Hook for extensible parsing.

From db68ec4dd0f0590db2275f0ca99ec24948983462 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 22:47:18 +0800
Subject: [PATCH v2 1/4] Add a parser_hook hook.

This does nothing but allow third-party plugins to implement a different
syntax, and fallback on the core parser if they don't implement a superset of
the supported core syntax.
---
 src/backend/tcop/postgres.c | 16 ++++++++++++++--
 src/include/tcop/tcopprot.h |  5 +++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 8cea10c901..e941b59b85 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -99,6 +99,9 @@ int			log_statement = LOGSTMT_NONE;
 /* GUC variable for maximum stack depth (measured in kilobytes) */
 int			max_stack_depth = 100;
 
+/* Hook for plugins to get control in pg_parse_query() */
+parser_hook_type parser_hook = NULL;
+
 /* wait N seconds to allow attach from a debugger */
 int			PostAuthDelay = 0;
 
@@ -589,18 +592,27 @@ ProcessClientWriteInterrupt(bool blocked)
  * database tables.  So, we rely on the raw parser to determine whether
  * we've seen a COMMIT or ABORT command; when we are in abort state, other
  * commands are not processed any further than the raw parse stage.
+ *
+ * To support loadable plugins that monitor the parsing or implements SQL
+ * syntactic sugar we provide a hook variable that lets a plugin get control
+ * before and after the standard parsing process.  If the plugin only implement
+ * a subset of postgres supported syntax, it's its duty to call raw_parser (or
+ * the previous hook if any) for the statements it doesn't understand.
  */
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list;
+	List	   *raw_parsetree_list = NIL;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	if (parser_hook)
+		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
+	else
+		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 968345404e..131dc2b22e 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -17,6 +17,7 @@
 #include "nodes/params.h"
 #include "nodes/parsenodes.h"
 #include "nodes/plannodes.h"
+#include "parser/parser.h"
 #include "storage/procsignal.h"
 #include "utils/guc.h"
 #include "utils/queryenvironment.h"
@@ -43,6 +44,10 @@ typedef enum
 
 extern PGDLLIMPORT int log_statement;
 
+/* Hook for plugins to get control in pg_parse_query() */
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+extern PGDLLIMPORT parser_hook_type parser_hook;
+
 extern List *pg_parse_query(const char *query_string);
 extern List *pg_rewrite_query(Query *query);
 extern List *pg_analyze_and_rewrite(RawStmt *parsetree,
-- 
2.31.1

From 3fb28880df308894cd2ce114f4b3cd97c90c03d6 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 23:54:02 +0800
Subject: [PATCH v2 2/4] Add a sqlol parser.

This is a toy example of alternative grammar that only accept a LOLCODE
compatible version of a

SELECT [column, ] column FROM tablename

and fallback on the core parser for everything else.
---
 contrib/Makefile                |   1 +
 contrib/sqlol/.gitignore        |   7 +
 contrib/sqlol/Makefile          |  33 ++
 contrib/sqlol/sqlol.c           | 107 +++++++
 contrib/sqlol/sqlol_gram.y      | 440 ++++++++++++++++++++++++++
 contrib/sqlol/sqlol_gramparse.h |  61 ++++
 contrib/sqlol/sqlol_keywords.c  |  98 ++++++
 contrib/sqlol/sqlol_keywords.h  |  38 +++
 contrib/sqlol/sqlol_kwlist.h    |  21 ++
 contrib/sqlol/sqlol_scan.l      | 544 ++++++++++++++++++++++++++++++++
 contrib/sqlol/sqlol_scanner.h   | 118 +++++++
 11 files changed, 1468 insertions(+)
 create mode 100644 contrib/sqlol/.gitignore
 create mode 100644 contrib/sqlol/Makefile
 create mode 100644 contrib/sqlol/sqlol.c
 create mode 100644 contrib/sqlol/sqlol_gram.y
 create mode 100644 contrib/sqlol/sqlol_gramparse.h
 create mode 100644 contrib/sqlol/sqlol_keywords.c
 create mode 100644 contrib/sqlol/sqlol_keywords.h
 create mode 100644 contrib/sqlol/sqlol_kwlist.h
 create mode 100644 contrib/sqlol/sqlol_scan.l
 create mode 100644 contrib/sqlol/sqlol_scanner.h

diff --git a/contrib/Makefile b/contrib/Makefile
index f27e458482..2a80cd137b 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -43,6 +43,7 @@ SUBDIRS = \
 		postgres_fdw	\
 		seg		\
 		spi		\
+		sqlol		\
 		tablefunc	\
 		tcn		\
 		test_decoding	\
diff --git a/contrib/sqlol/.gitignore b/contrib/sqlol/.gitignore
new file mode 100644
index 0000000000..3c4b587792
--- /dev/null
+++ b/contrib/sqlol/.gitignore
@@ -0,0 +1,7 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
+sqlol_gram.c
+sqlol_gram.h
+sqlol_scan.c
diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
new file mode 100644
index 0000000000..025e77c4ff
--- /dev/null
+++ b/contrib/sqlol/Makefile
@@ -0,0 +1,33 @@
+# contrib/sqlol/Makefile
+
+MODULE_big = sqlol
+OBJS = \
+	$(WIN32RES) \
+	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
+PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
+
+sqlol_gram.h: sqlol_gram.c
+	touch $@
+
+sqlol_gram.c: BISONFLAGS += -d
+# sqlol_gram.c: BISON_CHECK_CMD = $(PERL) $(srcdir)/check_keywords.pl $< $(top_srcdir)/src/include/parser/kwlist.h
+
+
+sqlol_scan.c: FLEXFLAGS = -CF -p -p
+sqlol_scan.c: FLEX_NO_BACKUP=yes
+sqlol_scan.c: FLEX_FIX_WARNING=yes
+
+
+# Force these dependencies to be known even without dependency info built:
+sqlol_gram.o sqlol_scan.o parser.o: sqlol_gram.h
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/sqlol
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
new file mode 100644
index 0000000000..b986966181
--- /dev/null
+++ b/contrib/sqlol/sqlol.c
@@ -0,0 +1,107 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol.c
+ *
+ *
+ * Copyright (c) 2008-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "tcop/tcopprot.h"
+
+#include "sqlol_gramparse.h"
+#include "sqlol_keywords.h"
+
+PG_MODULE_MAGIC;
+
+
+/* Saved hook values in case of unload */
+static parser_hook_type prev_parser_hook = NULL;
+
+void		_PG_init(void);
+void		_PG_fini(void);
+
+static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+
+
+/*
+ * Module load callback
+ */
+void
+_PG_init(void)
+{
+	/* Install hooks. */
+	prev_parser_hook = parser_hook;
+	parser_hook = sqlol_parser_hook;
+}
+
+/*
+ * Module unload callback
+ */
+void
+_PG_fini(void)
+{
+	/* Uninstall hooks. */
+	parser_hook = prev_parser_hook;
+}
+
+/*
+ * sqlol_parser_hook: parse our grammar
+ */
+static List *
+sqlol_parser_hook(const char *str, RawParseMode mode)
+{
+	sqlol_yyscan_t yyscanner;
+	sqlol_base_yy_extra_type yyextra;
+	int			yyresult;
+
+	if (mode != RAW_PARSE_DEFAULT)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	/* initialize the flex scanner */
+	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+
+	/* initialize the bison parser */
+	sqlol_parser_init(&yyextra);
+
+	/* Parse! */
+	yyresult = sqlol_base_yyparse(yyscanner);
+
+	/* Clean up (release memory) */
+	sqlol_scanner_finish(yyscanner);
+
+	/*
+	 * Invalid statement, fallback on previous parser_hook if any or
+	 * raw_parser()
+	 */
+	if (yyresult)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	return yyextra.parsetree;
+}
+
+int
+sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, sqlol_yyscan_t yyscanner)
+{
+	int			cur_token;
+
+	cur_token = sqlol_yylex(&(lvalp->sqlol_yystype), llocp, yyscanner);
+
+	return cur_token;
+}
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
new file mode 100644
index 0000000000..64d00d14ca
--- /dev/null
+++ b/contrib/sqlol/sqlol_gram.y
@@ -0,0 +1,440 @@
+%{
+
+/*#define YYDEBUG 1*/
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gram.y
+ *	  sqlol BISON rules/actions
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_gram.y
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "catalog/namespace.h"
+#include "nodes/makefuncs.h"
+
+#include "sqlol_gramparse.h"
+
+/*
+ * Location tracking support --- simpler than bison's default, since we only
+ * want to track the start position not the end position of each nonterminal.
+ */
+#define YYLLOC_DEFAULT(Current, Rhs, N) \
+	do { \
+		if ((N) > 0) \
+			(Current) = (Rhs)[1]; \
+		else \
+			(Current) = (-1); \
+	} while (0)
+
+/*
+ * The above macro assigns -1 (unknown) as the parse location of any
+ * nonterminal that was reduced from an empty rule, or whose leftmost
+ * component was reduced from an empty rule.  This is problematic
+ * for nonterminals defined like
+ *		OptFooList: / * EMPTY * / { ... } | OptFooList Foo { ... } ;
+ * because we'll set -1 as the location during the first reduction and then
+ * copy it during each subsequent reduction, leaving us with -1 for the
+ * location even when the list is not empty.  To fix that, do this in the
+ * action for the nonempty rule(s):
+ *		if (@$ < 0) @$ = @2;
+ * (Although we have many nonterminals that follow this pattern, we only
+ * bother with fixing @$ like this when the nonterminal's parse location
+ * is actually referenced in some rule.)
+ *
+ * A cleaner answer would be to make YYLLOC_DEFAULT scan all the Rhs
+ * locations until it's found one that's not -1.  Then we'd get a correct
+ * location for any nonterminal that isn't entirely empty.  But this way
+ * would add overhead to every rule reduction, and so far there's not been
+ * a compelling reason to pay that overhead.
+ */
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+
+#define parser_yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+#define parser_errposition(pos)  sqlol_scanner_errposition(pos, yyscanner)
+
+static void sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner,
+						 const char *msg);
+static RawStmt *makeRawStmt(Node *stmt, int stmt_location);
+static void updateRawStmtEnd(RawStmt *rs, int end_location);
+static Node *makeColumnRef(char *colname, List *indirection,
+						   int location, sqlol_yyscan_t yyscanner);
+static void check_qualified_name(List *names, sqlol_yyscan_t yyscanner);
+static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
+
+%}
+
+%pure-parser
+%expect 0
+%name-prefix="sqlol_base_yy"
+%locations
+
+%parse-param {sqlol_yyscan_t yyscanner}
+%lex-param   {sqlol_yyscan_t yyscanner}
+
+%union
+{
+	sqlol_YYSTYPE		sqlol_yystype;
+	/* these fields must match sqlol_YYSTYPE: */
+	int					ival;
+	char				*str;
+	const char			*keyword;
+
+	List				*list;
+	Node				*node;
+	Value				*value;
+	RangeVar			*range;
+	ResTarget			*target;
+}
+
+%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+				indirection_el
+
+%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+
+%type <range>	qualified_name
+
+%type <str>		ColId ColLabel attr_name
+
+%type <target>	gimmeh_el
+
+/*
+ * Non-keyword token types.  These are hard-wired into the "flex" lexer.
+ * They must be listed first so that their numeric codes do not depend on
+ * the set of keywords.  PL/pgSQL depends on this so that it can share the
+ * same lexer.  If you add/change tokens here, fix PL/pgSQL to match!
+ *
+ */
+%token <str>	IDENT FCONST SCONST Op
+
+/*
+ * If you want to make any keyword changes, update the keyword table in
+ * src/include/parser/kwlist.h and add new keywords to the appropriate one
+ * of the reserved-or-not-so-reserved keyword lists, below; search
+ * this file for "Keyword category lists".
+ */
+
+/* ordinary key words in alphabetical order */
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE
+
+
+%%
+
+/*
+ *	The target production for the whole parse.
+ *
+ * Ordinarily we parse a list of statements, but if we see one of the
+ * special MODE_XXX symbols as first token, we parse something else.
+ * The options here correspond to enum RawParseMode, which see for details.
+ */
+parse_toplevel:
+			stmtmulti
+			{
+				pg_yyget_extra(yyscanner)->parsetree = $1;
+			}
+		;
+
+/*
+ * At top level, we wrap each stmt with a RawStmt node carrying start location
+ * and length of the stmt's text.  Notice that the start loc/len are driven
+ * entirely from semicolon locations (@2).  It would seem natural to use
+ * @1 or @3 to get the true start location of a stmt, but that doesn't work
+ * for statements that can start with empty nonterminals (opt_with_clause is
+ * the main offender here); as noted in the comments for YYLLOC_DEFAULT,
+ * we'd get -1 for the location in such cases.
+ * We also take care to discard empty statements entirely.
+ */
+stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
+				{
+					if ($1 != NIL)
+					{
+						/* update length of previous stmt */
+						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
+					}
+					if ($3 != NULL)
+						$$ = lappend($1, makeRawStmt($3, @2 + 1));
+					else
+						$$ = $1;
+				}
+			| toplevel_stmt
+				{
+					if ($1 != NULL)
+						$$ = list_make1(makeRawStmt($1, 0));
+					else
+						$$ = NIL;
+				}
+		;
+
+/*
+ * toplevel_stmt includes BEGIN and END.  stmt does not include them, because
+ * those words have different meanings in function bodys.
+ */
+toplevel_stmt:
+			stmt
+		;
+
+stmt:
+			GimmehStmt
+			| /*EMPTY*/
+				{ $$ = NULL; }
+		;
+
+/*****************************************************************************
+ *
+ * GIMMEH statement
+ *
+ *****************************************************************************/
+
+GimmehStmt:
+			simple_gimmeh						{ $$ = $1; }
+		;
+
+simple_gimmeh:
+			HAI FCONST I HAS A qualified_name
+			GIMMEH gimmeh_list
+				{
+					SelectStmt *n = makeNode(SelectStmt);
+					n->targetList = $8;
+					n->fromClause = list_make1($6);
+					$$ = (Node *)n;
+				}
+		;
+
+gimmeh_list:
+		   gimmeh_el							{ $$ = list_make1($1); }
+		   | gimmeh_list ',' gimmeh_el			{ $$ = lappend($1, $3); }
+
+gimmeh_el:
+		 columnref
+			{
+				$$ = makeNode(ResTarget);
+				$$->name = NULL;
+				$$->indirection = NIL;
+				$$->val = (Node *)$1;
+				$$->location = @1;
+			}
+
+qualified_name:
+			ColId
+				{
+					$$ = makeRangeVar(NULL, $1, @1);
+				}
+			| ColId indirection
+				{
+					check_qualified_name($2, yyscanner);
+					$$ = makeRangeVar(NULL, NULL, @1);
+					switch (list_length($2))
+					{
+						case 1:
+							$$->catalogname = NULL;
+							$$->schemaname = $1;
+							$$->relname = strVal(linitial($2));
+							break;
+						case 2:
+							$$->catalogname = $1;
+							$$->schemaname = strVal(linitial($2));
+							$$->relname = strVal(lsecond($2));
+							break;
+						default:
+							/*
+							 * It's ok to error out here as at this point we
+							 * already parsed a "HAI FCONST" preamble, and no
+							 * other grammar is likely to accept a command
+							 * starting with that, so there's no point trying
+							 * to fall back on the other grammars.
+							 */
+							ereport(ERROR,
+									(errcode(ERRCODE_SYNTAX_ERROR),
+									 errmsg("improper qualified name (too many dotted names): %s",
+											NameListToString(lcons(makeString($1), $2))),
+									 parser_errposition(@1)));
+							break;
+					}
+				}
+		;
+
+columnref:	ColId
+				{
+					$$ = makeColumnRef($1, NIL, @1, yyscanner);
+				}
+			| ColId indirection
+				{
+					$$ = makeColumnRef($1, $2, @1, yyscanner);
+				}
+		;
+
+ColId:		IDENT									{ $$ = $1; }
+
+indirection:
+			indirection_el							{ $$ = list_make1($1); }
+			| indirection indirection_el			{ $$ = lappend($1, $2); }
+		;
+
+indirection_el:
+			'.' attr_name
+				{
+					$$ = (Node *) makeString($2);
+				}
+		;
+
+attr_name:	ColLabel								{ $$ = $1; };
+
+ColLabel:	IDENT									{ $$ = $1; }
+
+%%
+
+/*
+ * The signature of this function is required by bison.  However, we
+ * ignore the passed yylloc and instead use the last token position
+ * available from the scanner.
+ */
+static void
+sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner, const char *msg)
+{
+	parser_yyerror(msg);
+}
+
+static RawStmt *
+makeRawStmt(Node *stmt, int stmt_location)
+{
+	RawStmt    *rs = makeNode(RawStmt);
+
+	rs->stmt = stmt;
+	rs->stmt_location = stmt_location;
+	rs->stmt_len = 0;			/* might get changed later */
+	return rs;
+}
+
+/* Adjust a RawStmt to reflect that it doesn't run to the end of the string */
+static void
+updateRawStmtEnd(RawStmt *rs, int end_location)
+{
+	/*
+	 * If we already set the length, don't change it.  This is for situations
+	 * like "select foo ;; select bar" where the same statement will be last
+	 * in the string for more than one semicolon.
+	 */
+	if (rs->stmt_len > 0)
+		return;
+
+	/* OK, update length of RawStmt */
+	rs->stmt_len = end_location - rs->stmt_location;
+}
+
+static Node *
+makeColumnRef(char *colname, List *indirection,
+			  int location, sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * Generate a ColumnRef node, with an A_Indirection node added if there
+	 * is any subscripting in the specified indirection list.  However,
+	 * any field selection at the start of the indirection list must be
+	 * transposed into the "fields" part of the ColumnRef node.
+	 */
+	ColumnRef  *c = makeNode(ColumnRef);
+	int		nfields = 0;
+	ListCell *l;
+
+	c->location = location;
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Indices))
+		{
+			A_Indirection *i = makeNode(A_Indirection);
+
+			if (nfields == 0)
+			{
+				/* easy case - all indirection goes to A_Indirection */
+				c->fields = list_make1(makeString(colname));
+				i->indirection = check_indirection(indirection, yyscanner);
+			}
+			else
+			{
+				/* got to split the list in two */
+				i->indirection = check_indirection(list_copy_tail(indirection,
+																  nfields),
+												   yyscanner);
+				indirection = list_truncate(indirection, nfields);
+				c->fields = lcons(makeString(colname), indirection);
+			}
+			i->arg = (Node *) c;
+			return (Node *) i;
+		}
+		else if (IsA(lfirst(l), A_Star))
+		{
+			/* We only allow '*' at the end of a ColumnRef */
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+		nfields++;
+	}
+	/* No subscripting, so all indirection gets added to field list */
+	c->fields = lcons(makeString(colname), indirection);
+	return (Node *) c;
+}
+
+/* check_qualified_name --- check the result of qualified_name production
+ *
+ * It's easiest to let the grammar production for qualified_name allow
+ * subscripts and '*', which we then must reject here.
+ */
+static void
+check_qualified_name(List *names, sqlol_yyscan_t yyscanner)
+{
+	ListCell   *i;
+
+	foreach(i, names)
+	{
+		if (!IsA(lfirst(i), String))
+			parser_yyerror("syntax error");
+	}
+}
+
+/* check_indirection --- check the result of indirection production
+ *
+ * We only allow '*' at the end of the list, but it's hard to enforce that
+ * in the grammar, so do it here.
+ */
+static List *
+check_indirection(List *indirection, sqlol_yyscan_t yyscanner)
+{
+	ListCell *l;
+
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Star))
+		{
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+	}
+	return indirection;
+}
+
+/* sqlol_parser_init()
+ * Initialize to parse one query string
+ */
+void
+sqlol_parser_init(sqlol_base_yy_extra_type *yyext)
+{
+	yyext->parsetree = NIL;		/* in case grammar forgets to set it */
+}
diff --git a/contrib/sqlol/sqlol_gramparse.h b/contrib/sqlol/sqlol_gramparse.h
new file mode 100644
index 0000000000..58233a8d87
--- /dev/null
+++ b/contrib/sqlol/sqlol_gramparse.h
@@ -0,0 +1,61 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gramparse.h
+ *		Shared definitions for the "raw" parser (flex and bison phases only)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_gramparse.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_GRAMPARSE_H
+#define SQLOL_GRAMPARSE_H
+
+#include "nodes/parsenodes.h"
+#include "sqlol_scanner.h"
+
+/*
+ * NB: include gram.h only AFTER including scanner.h, because scanner.h
+ * is what #defines YYLTYPE.
+ */
+#include "sqlol_gram.h"
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.  Private
+ * state needed for raw parsing/lexing goes here.
+ */
+typedef struct sqlol_base_yy_extra_type
+{
+	/*
+	 * Fields used by the core scanner.
+	 */
+	sqlol_yy_extra_type sqlol_yy_extra;
+
+	/*
+	 * State variables that belong to the grammar.
+	 */
+	List	   *parsetree;		/* final parse result is delivered here */
+} sqlol_base_yy_extra_type;
+
+/*
+ * In principle we should use yyget_extra() to fetch the yyextra field
+ * from a yyscanner struct.  However, flex always puts that field first,
+ * and this is sufficiently performance-critical to make it seem worth
+ * cheating a bit to use an inline macro.
+ */
+#define pg_yyget_extra(yyscanner) (*((sqlol_base_yy_extra_type **) (yyscanner)))
+
+
+/* from parser.c */
+extern int	sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+
+/* from gram.y */
+extern void sqlol_parser_init(sqlol_base_yy_extra_type *yyext);
+extern int	sqlol_baseyyparse(sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_GRAMPARSE_H */
diff --git a/contrib/sqlol/sqlol_keywords.c b/contrib/sqlol/sqlol_keywords.c
new file mode 100644
index 0000000000..dbbdf5493c
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.c
@@ -0,0 +1,98 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.c
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  sqlol/sqlol_keywords.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "sqlol_gramparse.h"
+
+#define PG_KEYWORD(a,b,c) {a,b,c},
+
+const sqlol_ScanKeyword sqlol_ScanKeywords[] = {
+#include "sqlol_kwlist.h"
+};
+
+const int	sqlol_NumScanKeywords = lengthof(sqlol_ScanKeywords);
+
+#undef PG_KEYWORD
+
+
+/*
+ * ScanKeywordLookup - see if a given word is a keyword
+ *
+ * The table to be searched is passed explicitly, so that this can be used
+ * to search keyword lists other than the standard list appearing above.
+ *
+ * Returns a pointer to the sqlol_ScanKeyword table entry, or NULL if no match.
+ *
+ * The match is done case-insensitively.  Note that we deliberately use a
+ * dumbed-down case conversion that will only translate 'A'-'Z' into 'a'-'z',
+ * even if we are in a locale where tolower() would produce more or different
+ * translations.  This is to conform to the SQL99 spec, which says that
+ * keywords are to be matched in this way even though non-keyword identifiers
+ * receive a different case-normalization mapping.
+ */
+const sqlol_ScanKeyword *
+sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords)
+{
+	int			len,
+				i;
+	char		word[NAMEDATALEN];
+	const sqlol_ScanKeyword *low;
+	const sqlol_ScanKeyword *high;
+
+	len = strlen(text);
+	/* We assume all keywords are shorter than NAMEDATALEN. */
+	if (len >= NAMEDATALEN)
+		return NULL;
+
+	/*
+	 * Apply an ASCII-only downcasing.  We must not use tolower() since it may
+	 * produce the wrong translation in some locales (eg, Turkish).
+	 */
+	for (i = 0; i < len; i++)
+	{
+		char		ch = text[i];
+
+		if (ch >= 'A' && ch <= 'Z')
+			ch += 'a' - 'A';
+		word[i] = ch;
+	}
+	word[len] = '\0';
+
+	/*
+	 * Now do a binary search using plain strcmp() comparison.
+	 */
+	low = keywords;
+	high = keywords + (num_keywords - 1);
+	while (low <= high)
+	{
+		const sqlol_ScanKeyword *middle;
+		int			difference;
+
+		middle = low + (high - low) / 2;
+		difference = strcmp(middle->name, word);
+		if (difference == 0)
+			return middle;
+		else if (difference < 0)
+			low = middle + 1;
+		else
+			high = middle - 1;
+	}
+
+	return NULL;
+}
+
diff --git a/contrib/sqlol/sqlol_keywords.h b/contrib/sqlol/sqlol_keywords.h
new file mode 100644
index 0000000000..bc4acf4541
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.h
@@ -0,0 +1,38 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.h
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_keywords.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SQLOL_KEYWORDS_H
+#define SQLOL_KEYWORDS_H
+
+/* Keyword categories --- should match lists in gram.y */
+#define UNRESERVED_KEYWORD		0
+#define COL_NAME_KEYWORD		1
+#define TYPE_FUNC_NAME_KEYWORD	2
+#define RESERVED_KEYWORD		3
+
+
+typedef struct sqlol_ScanKeyword
+{
+	const char *name;			/* in lower case */
+	int16		value;			/* grammar's token code */
+	int16		category;		/* see codes above */
+} sqlol_ScanKeyword;
+
+extern PGDLLIMPORT const sqlol_ScanKeyword sqlol_ScanKeywords[];
+extern PGDLLIMPORT const int sqlol_NumScanKeywords;
+
+extern const sqlol_ScanKeyword *sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords);
+
+#endif							/* SQLOL_KEYWORDS_H */
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
new file mode 100644
index 0000000000..2de3893ee4
--- /dev/null
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -0,0 +1,21 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_kwlist.h
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_kwlist.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* name, value, category, is-bare-label */
+PG_KEYWORD("a", A, UNRESERVED_KEYWORD)
+PG_KEYWORD("gimmeh", GIMMEH, UNRESERVED_KEYWORD)
+PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
+PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
+PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
+PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
new file mode 100644
index 0000000000..a7088b8390
--- /dev/null
+++ b/contrib/sqlol/sqlol_scan.l
@@ -0,0 +1,544 @@
+%top{
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scan.l
+ *	  lexical scanner for sqlol
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_scan.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "common/string.h"
+#include "sqlol_gramparse.h"
+#include "parser/scansup.h"
+#include "mb/pg_wchar.h"
+
+#include "sqlol_keywords.h"
+}
+
+%{
+
+/* LCOV_EXCL_START */
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+
+/*
+ * Set the type of YYSTYPE.
+ */
+#define YYSTYPE sqlol_YYSTYPE
+
+/*
+ * Set the type of yyextra.  All state variables used by the scanner should
+ * be in yyextra, *not* statically allocated.
+ */
+#define YY_EXTRA_TYPE sqlol_yy_extra_type *
+
+/*
+ * Each call to yylex must set yylloc to the location of the found token
+ * (expressed as a byte offset from the start of the input text).
+ * When we parse a token that requires multiple lexer rules to process,
+ * this should be done in the first such rule, else yylloc will point
+ * into the middle of the token.
+ */
+#define SET_YYLLOC()  (*(yylloc) = yytext - yyextra->scanbuf)
+
+/*
+ * Advance yylloc by the given number of bytes.
+ */
+#define ADVANCE_YYLLOC(delta)  ( *(yylloc) += (delta) )
+
+/*
+ * Sometimes, we do want yylloc to point into the middle of a token; this is
+ * useful for instance to throw an error about an escape sequence within a
+ * string literal.  But if we find no error there, we want to revert yylloc
+ * to the token start, so that that's the location reported to the parser.
+ * Use PUSH_YYLLOC/POP_YYLLOC to save/restore yylloc around such code.
+ * (Currently the implied "stack" is just one location, but someday we might
+ * need to nest these.)
+ */
+#define PUSH_YYLLOC()	(yyextra->save_yylloc = *(yylloc))
+#define POP_YYLLOC()	(*(yylloc) = yyextra->save_yylloc)
+
+#define startlit()	( yyextra->literallen = 0 )
+static void addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner);
+static void addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner);
+static char *litbufdup(sqlol_yyscan_t yyscanner);
+
+#define yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+
+#define lexer_errposition()  sqlol_scanner_errposition(*(yylloc), yyscanner)
+
+/*
+ * Work around a bug in flex 2.5.35: it emits a couple of functions that
+ * it forgets to emit declarations for.  Since we use -Wmissing-prototypes,
+ * this would cause warnings.  Providing our own declarations should be
+ * harmless even when the bug gets fixed.
+ */
+extern int	sqlol_yyget_column(yyscan_t yyscanner);
+extern void sqlol_yyset_column(int column_no, yyscan_t yyscanner);
+
+%}
+
+%option reentrant
+%option bison-bridge
+%option bison-locations
+%option 8bit
+%option never-interactive
+%option nodefault
+%option noinput
+%option nounput
+%option noyywrap
+%option noyyalloc
+%option noyyrealloc
+%option noyyfree
+%option warn
+%option prefix="sqlol_yy"
+
+/*
+ * OK, here is a short description of lex/flex rules behavior.
+ * The longest pattern which matches an input string is always chosen.
+ * For equal-length patterns, the first occurring in the rules list is chosen.
+ * INITIAL is the starting state, to which all non-conditional rules apply.
+ * Exclusive states change parsing rules while the state is active.  When in
+ * an exclusive state, only those rules defined for that state apply.
+ *
+ * We use exclusive states for quoted strings, extended comments,
+ * and to eliminate parsing troubles for numeric strings.
+ * Exclusive states:
+ *  <xd> delimited identifiers (double-quoted identifiers)
+ *  <xq> standard quoted strings
+ *  <xqs> quote stop (detect continued strings)
+ *
+ * Remember to add an <<EOF>> case whenever you add a new exclusive state!
+ * The default one is probably not the right thing.
+ */
+
+%x xd
+%x xq
+%x xqs
+
+/*
+ * In order to make the world safe for Windows and Mac clients as well as
+ * Unix ones, we accept either \n or \r as a newline.  A DOS-style \r\n
+ * sequence will be seen as two successive newlines, but that doesn't cause
+ * any problems.  Comments that start with -- and extend to the next
+ * newline are treated as equivalent to a single whitespace character.
+ *
+ * NOTE a fine point: if there is no newline following --, we will absorb
+ * everything to the end of the input as a comment.  This is correct.  Older
+ * versions of Postgres failed to recognize -- as a comment if the input
+ * did not end with a newline.
+ *
+ * XXX perhaps \f (formfeed) should be treated as a newline as well?
+ *
+ * XXX if you change the set of whitespace characters, fix scanner_isspace()
+ * to agree.
+ */
+
+space			[ \t\n\r\f]
+horiz_space		[ \t\f]
+newline			[\n\r]
+non_newline		[^\n\r]
+
+comment			("--"{non_newline}*)
+
+whitespace		({space}+|{comment})
+
+/*
+ * SQL requires at least one newline in the whitespace separating
+ * string literals that are to be concatenated.  Silly, but who are we
+ * to argue?  Note that {whitespace_with_newline} should not have * after
+ * it, whereas {whitespace} should generally have a * after it...
+ */
+
+special_whitespace		({space}+|{comment}{newline})
+horiz_whitespace		({horiz_space}|{comment})
+whitespace_with_newline	({horiz_whitespace}*{newline}{special_whitespace}*)
+
+quote			'
+/* If we see {quote} then {quotecontinue}, the quoted string continues */
+quotecontinue	{whitespace_with_newline}{quote}
+
+/*
+ * {quotecontinuefail} is needed to avoid lexer backup when we fail to match
+ * {quotecontinue}.  It might seem that this could just be {whitespace}*,
+ * but if there's a dash after {whitespace_with_newline}, it must be consumed
+ * to see if there's another dash --- which would start a {comment} and thus
+ * allow continuation of the {quotecontinue} token.
+ */
+quotecontinuefail	{whitespace}*"-"?
+
+/* Extended quote
+ * xqdouble implements embedded quote, ''''
+ */
+xqstart			{quote}
+xqdouble		{quote}{quote}
+xqinside		[^']+
+
+/* Double quote
+ * Allows embedded spaces and other special characters into identifiers.
+ */
+dquote			\"
+xdstart			{dquote}
+xdstop			{dquote}
+xddouble		{dquote}{dquote}
+xdinside		[^"]+
+
+digit			[0-9]
+ident_start		[A-Za-z\200-\377_]
+ident_cont		[A-Za-z\200-\377_0-9\$]
+
+identifier		{ident_start}{ident_cont}*
+
+decimal			(({digit}+)|({digit}*\.{digit}+)|({digit}+\.{digit}*))
+
+other			.
+
+%%
+
+{whitespace}	{
+					/* ignore */
+				}
+
+
+{xqstart}		{
+					yyextra->saw_non_ascii = false;
+					SET_YYLLOC();
+					BEGIN(xq);
+					startlit();
+}
+<xq>{quote} {
+					/*
+					 * When we are scanning a quoted string and see an end
+					 * quote, we must look ahead for a possible continuation.
+					 * If we don't see one, we know the end quote was in fact
+					 * the end of the string.  To reduce the lexer table size,
+					 * we use a single "xqs" state to do the lookahead for all
+					 * types of strings.
+					 */
+					yyextra->state_before_str_stop = YYSTATE;
+					BEGIN(xqs);
+				}
+<xqs>{quotecontinue} {
+					/*
+					 * Found a quote continuation, so return to the in-quote
+					 * state and continue scanning the literal.  Nothing is
+					 * added to the literal's contents.
+					 */
+					BEGIN(yyextra->state_before_str_stop);
+				}
+<xqs>{quotecontinuefail} |
+<xqs>{other} |
+<xqs><<EOF>>	{
+					/*
+					 * Failed to see a quote continuation.  Throw back
+					 * everything after the end quote, and handle the string
+					 * according to the state we were in previously.
+					 */
+					yyless(0);
+					BEGIN(INITIAL);
+
+					switch (yyextra->state_before_str_stop)
+					{
+						case xq:
+							/*
+							 * Check that the data remains valid, if it might
+							 * have been made invalid by unescaping any chars.
+							 */
+							if (yyextra->saw_non_ascii)
+								pg_verifymbstr(yyextra->literalbuf,
+										yyextra->literallen,
+										false);
+							yylval->str = litbufdup(yyscanner);
+							return SCONST;
+						default:
+							yyerror("unhandled previous state in xqs");
+					}
+				}
+
+<xq>{xqdouble} {
+					addlitchar('\'', yyscanner);
+				}
+<xq>{xqinside}  {
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xq><<EOF>>		{ yyerror("unterminated quoted string"); }
+
+
+{xdstart}		{
+					SET_YYLLOC();
+					BEGIN(xd);
+					startlit();
+				}
+<xd>{xdstop}	{
+					char	   *ident;
+
+					BEGIN(INITIAL);
+					if (yyextra->literallen == 0)
+						yyerror("zero-length delimited identifier");
+					ident = litbufdup(yyscanner);
+					if (yyextra->literallen >= NAMEDATALEN)
+						truncate_identifier(ident, yyextra->literallen, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+<xd>{xddouble}	{
+					addlitchar('"', yyscanner);
+				}
+<xd>{xdinside}	{
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xd><<EOF>>		{ yyerror("unterminated quoted identifier"); }
+
+{decimal}		{
+					SET_YYLLOC();
+					yylval->str = pstrdup(yytext);
+					return FCONST;
+				}
+
+{identifier}	{
+					const sqlol_ScanKeyword *keyword;
+					char	   *ident;
+
+					SET_YYLLOC();
+
+					/* Is it a keyword? */
+					keyword = sqlol_ScanKeywordLookup(yytext,
+													yyextra->keywords,
+													yyextra->num_keywords);
+					if (keyword != NULL)
+					{
+						yylval->keyword = keyword->name;
+						return keyword->value;
+					}
+
+					/*
+					 * No.  Convert the identifier to lower case, and truncate
+					 * if necessary.
+					 */
+					ident = downcase_truncate_identifier(yytext, yyleng, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+
+{other}			{
+					SET_YYLLOC();
+					return yytext[0];
+				}
+
+<<EOF>>			{
+					SET_YYLLOC();
+					yyterminate();
+				}
+
+%%
+
+/* LCOV_EXCL_STOP */
+
+/*
+ * Arrange access to yyextra for subroutines of the main yylex() function.
+ * We expect each subroutine to have a yyscanner parameter.  Rather than
+ * use the yyget_xxx functions, which might or might not get inlined by the
+ * compiler, we cheat just a bit and cast yyscanner to the right type.
+ */
+#undef yyextra
+#define yyextra  (((struct yyguts_t *) yyscanner)->yyextra_r)
+
+/* Likewise for a couple of other things we need. */
+#undef yylloc
+#define yylloc	(((struct yyguts_t *) yyscanner)->yylloc_r)
+#undef yyleng
+#define yyleng	(((struct yyguts_t *) yyscanner)->yyleng_r)
+
+
+/*
+ * scanner_errposition
+ *		Report a lexer or grammar error cursor position, if possible.
+ *
+ * This is expected to be used within an ereport() call.  The return value
+ * is a dummy (always 0, in fact).
+ *
+ * Note that this can only be used for messages emitted during raw parsing
+ * (essentially, sqlol_scan.l, sqlol_parser.c, sqlol_and gram.y), since it
+ * requires the yyscanner struct to still be available.
+ */
+int
+sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner)
+{
+	int			pos;
+
+	if (location < 0)
+		return 0;				/* no-op if location is unknown */
+
+	/* Convert byte offset to character number */
+	pos = pg_mbstrlen_with_len(yyextra->scanbuf, location) + 1;
+	/* And pass it to the ereport mechanism */
+	return errposition(pos);
+}
+
+/*
+ * scanner_yyerror
+ *		Report a lexer or grammar error.
+ *
+ * Just ignore as we'll fallback to raw_parser().
+ */
+void
+sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner)
+{
+	return;
+}
+
+
+/*
+ * Called before any actual parsing is done
+ */
+sqlol_yyscan_t
+sqlol_scanner_init(const char *str,
+			 sqlol_yy_extra_type *yyext,
+			 const sqlol_ScanKeyword *keywords,
+			 int num_keywords)
+{
+	Size		slen = strlen(str);
+	yyscan_t	scanner;
+
+	if (yylex_init(&scanner) != 0)
+		elog(ERROR, "yylex_init() failed: %m");
+
+	sqlol_yyset_extra(yyext, scanner);
+
+	yyext->keywords = keywords;
+	yyext->num_keywords = num_keywords;
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	yyext->scanbuf = (char *) palloc(slen + 2);
+	yyext->scanbuflen = slen;
+	memcpy(yyext->scanbuf, str, slen);
+	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+
+	/* initialize literal buffer to a reasonable but expansible size */
+	yyext->literalalloc = 1024;
+	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
+	yyext->literallen = 0;
+
+	return scanner;
+}
+
+
+/*
+ * Called after parsing is done to clean up after scanner_init()
+ */
+void
+sqlol_scanner_finish(sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * We don't bother to call yylex_destroy(), because all it would do is
+	 * pfree a small amount of control storage.  It's cheaper to leak the
+	 * storage until the parsing context is destroyed.  The amount of space
+	 * involved is usually negligible compared to the output parse tree
+	 * anyway.
+	 *
+	 * We do bother to pfree the scanbuf and literal buffer, but only if they
+	 * represent a nontrivial amount of space.  The 8K cutoff is arbitrary.
+	 */
+	if (yyextra->scanbuflen >= 8192)
+		pfree(yyextra->scanbuf);
+	if (yyextra->literalalloc >= 8192)
+		pfree(yyextra->literalbuf);
+}
+
+
+static void
+addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + yleng) >= yyextra->literalalloc)
+	{
+		do
+		{
+			yyextra->literalalloc *= 2;
+		} while ((yyextra->literallen + yleng) >= yyextra->literalalloc);
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	memcpy(yyextra->literalbuf + yyextra->literallen, ytext, yleng);
+	yyextra->literallen += yleng;
+}
+
+
+static void
+addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + 1) >= yyextra->literalalloc)
+	{
+		yyextra->literalalloc *= 2;
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	yyextra->literalbuf[yyextra->literallen] = ychar;
+	yyextra->literallen += 1;
+}
+
+
+/*
+ * Create a palloc'd copy of literalbuf, adding a trailing null.
+ */
+static char *
+litbufdup(sqlol_yyscan_t yyscanner)
+{
+	int			llen = yyextra->literallen;
+	char	   *new;
+
+	new = palloc(llen + 1);
+	memcpy(new, yyextra->literalbuf, llen);
+	new[llen] = '\0';
+	return new;
+}
+
+/*
+ * Interface functions to make flex use palloc() instead of malloc().
+ * It'd be better to make these static, but flex insists otherwise.
+ */
+
+void *
+sqlol_yyalloc(yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	return palloc(bytes);
+}
+
+void *
+sqlol_yyrealloc(void *ptr, yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		return repalloc(ptr, bytes);
+	else
+		return palloc(bytes);
+}
+
+void
+sqlol_yyfree(void *ptr, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		pfree(ptr);
+}
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
new file mode 100644
index 0000000000..0a497e9d91
--- /dev/null
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -0,0 +1,118 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scanner.h
+ *		API for the core scanner (flex machine)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_scanner.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_SCANNER_H
+#define SQLOL_SCANNER_H
+
+#include "sqlol_keywords.h"
+
+/*
+ * The scanner returns extra data about scanned tokens in this union type.
+ * Note that this is a subset of the fields used in YYSTYPE of the bison
+ * parsers built atop the scanner.
+ */
+typedef union sqlol_YYSTYPE
+{
+	int			ival;			/* for integer literals */
+	char	   *str;			/* for identifiers and non-integer literals */
+	const char *keyword;		/* canonical spelling of keywords */
+} sqlol_YYSTYPE;
+
+/*
+ * We track token locations in terms of byte offsets from the start of the
+ * source string, not the column number/line number representation that
+ * bison uses by default.  Also, to minimize overhead we track only one
+ * location (usually the first token location) for each construct, not
+ * the beginning and ending locations as bison does by default.  It's
+ * therefore sufficient to make YYLTYPE an int.
+ */
+#define YYLTYPE  int
+
+/*
+ * Another important component of the scanner's API is the token code numbers.
+ * However, those are not defined in this file, because bison insists on
+ * defining them for itself.  The token codes used by the core scanner are
+ * the ASCII characters plus these:
+ *	%token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
+ *	%token <ival>	ICONST PARAM
+ *	%token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
+ *	%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+ * The above token definitions *must* be the first ones declared in any
+ * bison parser built atop this scanner, so that they will have consistent
+ * numbers assigned to them (specifically, IDENT = 258 and so on).
+ */
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.
+ * Private state needed by the core scanner goes here.  Note that the actual
+ * yy_extra struct may be larger and have this as its first component, thus
+ * allowing the calling parser to keep some fields of its own in YY_EXTRA.
+ */
+typedef struct sqlol_yy_extra_type
+{
+	/*
+	 * The string the scanner is physically scanning.  We keep this mainly so
+	 * that we can cheaply compute the offset of the current token (yytext).
+	 */
+	char	   *scanbuf;
+	Size		scanbuflen;
+
+	/*
+	 * The keyword list to use, and the associated grammar token codes.
+	 */
+	const sqlol_ScanKeyword *keywords;
+	int		num_keywords;
+
+	/*
+	 * literalbuf is used to accumulate literal values when multiple rules are
+	 * needed to parse a single literal.  Call startlit() to reset buffer to
+	 * empty, addlit() to add text.  NOTE: the string in literalbuf is NOT
+	 * necessarily null-terminated, but there always IS room to add a trailing
+	 * null at offset literallen.  We store a null only when we need it.
+	 */
+	char	   *literalbuf;		/* palloc'd expandable buffer */
+	int			literallen;		/* actual current string length */
+	int			literalalloc;	/* current allocated buffer size */
+
+	/*
+	 * Random assorted scanner state.
+	 */
+	int			state_before_str_stop;	/* start cond. before end quote */
+	YYLTYPE		save_yylloc;	/* one-element stack for PUSH_YYLLOC() */
+
+	/* state variables for literal-lexing warnings */
+	bool		saw_non_ascii;
+} sqlol_yy_extra_type;
+
+/*
+ * The type of yyscanner is opaque outside scan.l.
+ */
+typedef void *sqlol_yyscan_t;
+
+
+/* Constant data exported from parser/scan.l */
+extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
+
+/* Entry points in parser/scan.l */
+extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
+								  sqlol_yy_extra_type *yyext,
+								  const sqlol_ScanKeyword *keywords,
+								  int num_keywords);
+extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
+extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+extern int	sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner);
+extern void sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_SCANNER_H */
-- 
2.31.1

From 767ef007e65e44a5a2db7018fb759b29796c5f41 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 01:33:42 +0800
Subject: [PATCH v2 3/4] Add a new MODE_SINGLE_QUERY to the core parser and use
 it in pg_parse_query.

If a third-party module provides a parser_hook, pg_parse_query() switches to
single-query parsing so multi-query commands using different grammar can work
properly.  If the third-party module supports the full set of SQL we support,
or want to prevent fallback on the core parser, it can ignore the
MODE_SINGLE_QUERY mode and parse the full query string.  In that case they must
return a List with more than one RawStmt or a single RawStmt with a 0 length to
stop the parsing phase, or raise an ERROR.

Otherwise, plugins should parse a single query only and always return a List
containing a single RawStmt with a properly set length (possibly 0 if it was a
single query without end of query delimiter).  If the command is valid but
doesn't contain any statements (e.g. a single semi-colon), a single RawStmt
with a NULL stmt field should be returned, containing the consumed query string
length so we can move to the next command in a single pass rather than 1 byte
at a time.

Also, third-party modules can choose to ignore some or all of parsing error if
they want to implement only subset of postgres suppoted syntax, or even a
totally different syntax, and fall-back on core grammar for unhandled case.  In
thase case, they should set the error flag to true.  The returned List will be
ignored and the same offset of the input string will be parsed using the core
parser.

Finally, note that third-party plugins that wants to fallback on other grammar
should first try to call a previous parser hook if any before setting the error
switch and returning.
---
 .../pg_stat_statements/pg_stat_statements.c   |   3 +-
 src/backend/commands/tablecmds.c              |   2 +-
 src/backend/executor/spi.c                    |   4 +-
 src/backend/parser/gram.y                     |  29 +++-
 src/backend/parser/parse_type.c               |   2 +-
 src/backend/parser/parser.c                   |  15 +-
 src/backend/parser/scan.l                     |  26 +++-
 src/backend/tcop/postgres.c                   | 138 ++++++++++++++++--
 src/include/parser/parser.h                   |   5 +-
 src/include/parser/scanner.h                  |   6 +-
 src/include/tcop/tcopprot.h                   |   3 +-
 src/pl/plpgsql/src/pl_gram.y                  |   2 +-
 src/pl/plpgsql/src/pl_scanner.c               |   2 +-
 13 files changed, 210 insertions(+), 27 deletions(-)

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 09433c8c96..d852575613 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -2718,7 +2718,8 @@ fill_in_constant_lengths(JumbleState *jstate, const char *query,
 	yyscanner = scanner_init(query,
 							 &yyextra,
 							 &ScanKeywords,
-							 ScanKeywordTokens);
+							 ScanKeywordTokens,
+							 0);
 
 	/* we don't want to re-emit any escape string warnings */
 	yyextra.escape_string_warning = false;
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 028e8ac46b..284933c693 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -12677,7 +12677,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 	 * parse_analyze() or the rewriter, but instead we need to pass them
 	 * through parse_utilcmd.c to make them ready for execution.
 	 */
-	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT);
+	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT, 0);
 	querytree_list = NIL;
 	foreach(list_item, raw_parsetree_list)
 	{
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index b8bd05e894..f05b3ce9e7 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -2120,7 +2120,7 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Do parse analysis and rule rewrite for each raw parsetree, storing the
@@ -2228,7 +2228,7 @@ _SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Construct plancache entries, but don't do parse analysis yet.
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 9ee90e3f13..2cac062ef4 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -626,7 +626,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
 %token <ival>	ICONST PARAM
 %token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
-%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS END_OF_FILE
 
 /*
  * If you want to make any keyword changes, update the keyword table in
@@ -753,6 +753,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token		MODE_PLPGSQL_ASSIGN1
 %token		MODE_PLPGSQL_ASSIGN2
 %token		MODE_PLPGSQL_ASSIGN3
+%token		MODE_SINGLE_QUERY
 
 
 /* Precedence: lowest to highest */
@@ -858,6 +859,32 @@ parse_toplevel:
 				pg_yyget_extra(yyscanner)->parsetree =
 					list_make1(makeRawStmt((Node *) n, 0));
 			}
+			| MODE_SINGLE_QUERY toplevel_stmt ';'
+			{
+				RawStmt *raw = makeRawStmt($2, 0);
+				updateRawStmtEnd(raw, @3 + 1);
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string and move to the next command.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(raw);
+				YYACCEPT;
+			}
+			/*
+			 * We need to explicitly look for EOF to parse non-semicolon
+			 * terminated statements in single query mode, as we could
+			 * otherwise successfully parse the beginning of an otherwise
+			 * invalid query.
+			 */
+			| MODE_SINGLE_QUERY toplevel_stmt END_OF_FILE
+			{
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(makeRawStmt($2, 0));
+				YYACCEPT;
+			}
 		;
 
 /*
diff --git a/src/backend/parser/parse_type.c b/src/backend/parser/parse_type.c
index abe131ebeb..e9a7b5d62a 100644
--- a/src/backend/parser/parse_type.c
+++ b/src/backend/parser/parse_type.c
@@ -746,7 +746,7 @@ typeStringToTypeName(const char *str)
 	ptserrcontext.previous = error_context_stack;
 	error_context_stack = &ptserrcontext;
 
-	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME);
+	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME, 0);
 
 	error_context_stack = ptserrcontext.previous;
 
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index 875de7ba28..418c50ee8f 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -37,17 +37,25 @@ static char *str_udeescape(const char *str, char escape,
  *
  * Returns a list of raw (un-analyzed) parse trees.  The contents of the
  * list have the form required by the specified RawParseMode.
+ *
+ * For all mode different from MODE_SINGLE_QUERY, caller should provide a 0
+ * offset as the whole input string should be parsed.  Otherwise, caller should
+ * provide the wanted offset in the input string, or -1 if no offset is
+ * required.
  */
 List *
-raw_parser(const char *str, RawParseMode mode)
+raw_parser(const char *str, RawParseMode mode, int offset)
 {
 	core_yyscan_t yyscanner;
 	base_yy_extra_type yyextra;
 	int			yyresult;
 
+	Assert((mode != MODE_SINGLE_QUERY && offset == 0) ||
+			(mode == MODE_SINGLE_QUERY && offset != 0));
+
 	/* initialize the flex scanner */
 	yyscanner = scanner_init(str, &yyextra.core_yy_extra,
-							 &ScanKeywords, ScanKeywordTokens);
+							 &ScanKeywords, ScanKeywordTokens, offset);
 
 	/* base_yylex() only needs us to initialize the lookahead token, if any */
 	if (mode == RAW_PARSE_DEFAULT)
@@ -61,7 +69,8 @@ raw_parser(const char *str, RawParseMode mode)
 			MODE_PLPGSQL_EXPR,	/* RAW_PARSE_PLPGSQL_EXPR */
 			MODE_PLPGSQL_ASSIGN1,	/* RAW_PARSE_PLPGSQL_ASSIGN1 */
 			MODE_PLPGSQL_ASSIGN2,	/* RAW_PARSE_PLPGSQL_ASSIGN2 */
-			MODE_PLPGSQL_ASSIGN3	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_PLPGSQL_ASSIGN3,	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_SINGLE_QUERY		/* RAW_PARSE_SINGLE_QUERY */
 		};
 
 		yyextra.have_lookahead = true;
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
index 9f9d8a1706..8ccbe95ac6 100644
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -1041,7 +1041,10 @@ other			.
 
 <<EOF>>			{
 					SET_YYLLOC();
-					yyterminate();
+					if (yyextra->return_eof)
+						return END_OF_FILE;
+					else
+						yyterminate();
 				}
 
 %%
@@ -1189,8 +1192,10 @@ core_yyscan_t
 scanner_init(const char *str,
 			 core_yy_extra_type *yyext,
 			 const ScanKeywordList *keywordlist,
-			 const uint16 *keyword_tokens)
+			 const uint16 *keyword_tokens,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -1213,13 +1218,28 @@ scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Note that pg_parse_query will set a -1 offset rather than 0 for the
+	 * first query of a possibly multi-query string if it wants us to return an
+	 * EOF token.
+	 */
+	yyext->return_eof = (offset != 0);
+
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	if (offset > 0)
+		state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index e941b59b85..9331628add 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -602,17 +602,137 @@ ProcessClientWriteInterrupt(bool blocked)
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list = NIL;
+	List		   *result = NIL;
+	int				stmt_len, offset;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	if (parser_hook)
-		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
-	else
-		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	stmt_len = 0; /* lazily computed when needed */
+	offset = 0;
+
+	while(true)
+	{
+		List *raw_parsetree_list;
+		RawStmt *raw;
+		bool	error = false;
+
+		/*----------------
+		 * Start parsing the input string.  If a third-party module provided a
+		 * parser_hook, we switch to single-query parsing so multi-query
+		 * commands using different grammar can work properly.
+		 * If the third-party modules support the full set of SQL we support,
+		 * or want to prevent fallback on the core parser, it can ignore the
+		 * RAW_PARSE_SINGLE_QUERY flag and parse the full query string.
+		 * In that case they must return a List with more than one RawStmt or a
+		 * single RawStmt with a 0 length to stop the parsing phase, or raise
+		 * an ERROR.
+		 *
+		 * Otherwise, plugins should parse a single query only and always
+		 * return a List containing a single RawStmt with a properly set length
+		 * (possibly 0 if it was a single query without end of query
+		 * delimiter).  If the command is valid but doesn't contain any
+		 * statements (e.g. a single semi-colon), a single RawStmt with a NULL
+		 * stmt field should be returned, containing the consumed query string
+		 * length so we can move to the next command in a single pass rather
+		 * than 1 byte at a time.
+		 *
+		 * Also, third-party modules can choose to ignore some or all of
+		 * parsing error if they want to implement only subset of postgres
+		 * suppoted syntax, or even a totally different syntax, and fall-back
+		 * on core grammar for unhandled case.  In thase case, they should set
+		 * the error flag to true.  The returned List will be ignored and the
+		 * same offset of the input string will be parsed using the core
+		 * parser.
+		 *
+		 * Finally, note that third-party modules that wants to fallback on
+		 * other grammar should first try to call a previous parser hook if any
+		 * before setting the error switch and returning .
+		 */
+		if (parser_hook)
+			raw_parsetree_list = (*parser_hook) (query_string,
+												 RAW_PARSE_SINGLE_QUERY,
+												 offset,
+												 &error);
+
+		/*
+		 * If a third-party module couldn't parse a single query or if no
+		 * third-party module is configured, fallback on core parser.
+		 */
+		if (error || !parser_hook)
+		{
+			/* Send a -1 offset to raw_parser to specify that it should
+			 * explicitly detect EOF during parsing.  scanner_init() will treat
+			 * it the same as a 0 offset.
+			 */
+			raw_parsetree_list = raw_parser(query_string,
+					error ? RAW_PARSE_SINGLE_QUERY : RAW_PARSE_DEFAULT,
+					(error && offset == 0) ? -1 : offset);
+		}
+
+		/*
+		 * If there are no third-party plugin, or none of the parsers found a
+		 * valid query, or if a third party module consumed the whole
+		 * query string we're done.
+		 */
+		if (!parser_hook || raw_parsetree_list == NIL ||
+			list_length(raw_parsetree_list) > 1)
+		{
+			/*
+			 * Warn third-party plugins if they mix "single query" and "whole
+			 * input string" strategy rather than silently accepting it and
+			 * maybe allow fallback on core grammar even if they want to avoid
+			 * that.  This way plugin authors can be warned early of the issue.
+			 */
+			if (result != NIL)
+			{
+				Assert(parser_hook != NULL);
+				elog(ERROR, "parser_hook should parse a single statement at "
+						"a time or consume the whole input string at once");
+			}
+			result = raw_parsetree_list;
+			break;
+		}
+
+		if (stmt_len == 0)
+			stmt_len = strlen(query_string);
+
+		raw = linitial_node(RawStmt, raw_parsetree_list);
+
+		/*
+		 * In single-query mode, the parser will return statement location info
+		 * relative to the beginning of complete original string, not the part
+		 * we just parsed, so adjust the location info.
+		 */
+		if (offset > 0 && raw->stmt_len > 0)
+		{
+			Assert(raw->stmt_len > offset);
+			raw->stmt_location = offset;
+			raw->stmt_len -= offset;
+		}
+
+		/* Ignore the statement if it didn't contain any command. */
+		if (raw->stmt)
+			result = lappend(result, raw);
+
+		if (raw->stmt_len == 0)
+		{
+			/* The statement was the whole string, we're done. */
+			break;
+		}
+		else if (raw->stmt_len + offset >= stmt_len)
+		{
+			/* We consumed all of the input string, we're done. */
+			break;
+		}
+		else
+		{
+			/* Advance the offset to the next command. */
+			offset += raw->stmt_len;
+		}
+	}
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
@@ -620,13 +740,13 @@ pg_parse_query(const char *query_string)
 #ifdef COPY_PARSE_PLAN_TREES
 	/* Optional debugging check: pass raw parsetrees through copyObject() */
 	{
-		List	   *new_list = copyObject(raw_parsetree_list);
+		List	   *new_list = copyObject(result);
 
 		/* This checks both copyObject() and the equal() routines... */
-		if (!equal(new_list, raw_parsetree_list))
+		if (!equal(new_list, result))
 			elog(WARNING, "copyObject() failed to produce an equal raw parse tree");
 		else
-			raw_parsetree_list = new_list;
+			result = new_list;
 	}
 #endif
 
@@ -638,7 +758,7 @@ pg_parse_query(const char *query_string)
 
 	TRACE_POSTGRESQL_QUERY_PARSE_DONE(query_string);
 
-	return raw_parsetree_list;
+	return result;
 }
 
 /*
diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h
index 853b0f1606..5694ae791a 100644
--- a/src/include/parser/parser.h
+++ b/src/include/parser/parser.h
@@ -41,7 +41,8 @@ typedef enum
 	RAW_PARSE_PLPGSQL_EXPR,
 	RAW_PARSE_PLPGSQL_ASSIGN1,
 	RAW_PARSE_PLPGSQL_ASSIGN2,
-	RAW_PARSE_PLPGSQL_ASSIGN3
+	RAW_PARSE_PLPGSQL_ASSIGN3,
+	RAW_PARSE_SINGLE_QUERY
 } RawParseMode;
 
 /* Values for the backslash_quote GUC */
@@ -59,7 +60,7 @@ extern PGDLLIMPORT bool standard_conforming_strings;
 
 
 /* Primary entry point for the raw parsing functions */
-extern List *raw_parser(const char *str, RawParseMode mode);
+extern List *raw_parser(const char *str, RawParseMode mode, int offset);
 
 /* Utility functions exported by gram.y (perhaps these should be elsewhere) */
 extern List *SystemFuncName(char *name);
diff --git a/src/include/parser/scanner.h b/src/include/parser/scanner.h
index 0d8182faa0..a2e97be5d5 100644
--- a/src/include/parser/scanner.h
+++ b/src/include/parser/scanner.h
@@ -113,6 +113,9 @@ typedef struct core_yy_extra_type
 	/* state variables for literal-lexing warnings */
 	bool		warn_on_first_escape;
 	bool		saw_non_ascii;
+
+	/* state variable for returning an EOF token in single query mode */
+	bool		return_eof;
 } core_yy_extra_type;
 
 /*
@@ -136,7 +139,8 @@ extern PGDLLIMPORT const uint16 ScanKeywordTokens[];
 extern core_yyscan_t scanner_init(const char *str,
 								  core_yy_extra_type *yyext,
 								  const ScanKeywordList *keywordlist,
-								  const uint16 *keyword_tokens);
+								  const uint16 *keyword_tokens,
+								  int offset);
 extern void scanner_finish(core_yyscan_t yyscanner);
 extern int	core_yylex(core_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   core_yyscan_t yyscanner);
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 131dc2b22e..27201dde1d 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -45,7 +45,8 @@ typedef enum
 extern PGDLLIMPORT int log_statement;
 
 /* Hook for plugins to get control in pg_parse_query() */
-typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode,
+								   int offset, bool *error);
 extern PGDLLIMPORT parser_hook_type parser_hook;
 
 extern List *pg_parse_query(const char *query_string);
diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y
index 3fcca43b90..e5a8a6477a 100644
--- a/src/pl/plpgsql/src/pl_gram.y
+++ b/src/pl/plpgsql/src/pl_gram.y
@@ -3656,7 +3656,7 @@ check_sql_expr(const char *stmt, RawParseMode parseMode, int location)
 	error_context_stack = &syntax_errcontext;
 
 	oldCxt = MemoryContextSwitchTo(plpgsql_compile_tmp_cxt);
-	(void) raw_parser(stmt, parseMode);
+	(void) raw_parser(stmt, parseMode, 0);
 	MemoryContextSwitchTo(oldCxt);
 
 	/* Restore former ereport callback */
diff --git a/src/pl/plpgsql/src/pl_scanner.c b/src/pl/plpgsql/src/pl_scanner.c
index e4c7a91ab5..a2886c42ec 100644
--- a/src/pl/plpgsql/src/pl_scanner.c
+++ b/src/pl/plpgsql/src/pl_scanner.c
@@ -587,7 +587,7 @@ plpgsql_scanner_init(const char *str)
 {
 	/* Start up the core scanner */
 	yyscanner = scanner_init(str, &core_yy,
-							 &ReservedPLKeywords, ReservedPLKeywordTokens);
+							 &ReservedPLKeywords, ReservedPLKeywordTokens, 0);
 
 	/*
 	 * scanorig points to the original string, which unlike the scanner's
-- 
2.31.1

From 36506de98e53432f13c4ca0b6b9907371fa133a6 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 02:15:54 +0800
Subject: [PATCH v2 4/4] Teach sqlol to use the new MODE_SINGLE_QUERY parser
 mode.

This way multi-statements commands using both core parser and sqlol parser can
be supported.

Also add a LOLCODE version of CREATE VIEW viewname AS to easily test
multi-statements commands.
---
 contrib/sqlol/Makefile              |  2 +
 contrib/sqlol/expected/01_sqlol.out | 74 +++++++++++++++++++++++++++++
 contrib/sqlol/repro.sql             | 18 +++++++
 contrib/sqlol/sql/01_sqlol.sql      | 40 ++++++++++++++++
 contrib/sqlol/sqlol.c               | 24 ++++++----
 contrib/sqlol/sqlol_gram.y          | 63 ++++++++++++------------
 contrib/sqlol/sqlol_kwlist.h        |  1 +
 contrib/sqlol/sqlol_scan.l          | 13 ++++-
 contrib/sqlol/sqlol_scanner.h       |  3 +-
 9 files changed, 192 insertions(+), 46 deletions(-)
 create mode 100644 contrib/sqlol/expected/01_sqlol.out
 create mode 100644 contrib/sqlol/repro.sql
 create mode 100644 contrib/sqlol/sql/01_sqlol.sql

diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
index 025e77c4ff..554fe91eae 100644
--- a/contrib/sqlol/Makefile
+++ b/contrib/sqlol/Makefile
@@ -6,6 +6,8 @@ OBJS = \
 	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
 PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
 
+REGRESS = 01_sqlol
+
 sqlol_gram.h: sqlol_gram.c
 	touch $@
 
diff --git a/contrib/sqlol/expected/01_sqlol.out b/contrib/sqlol/expected/01_sqlol.out
new file mode 100644
index 0000000000..a18eaf6801
--- /dev/null
+++ b/contrib/sqlol/expected/01_sqlol.out
@@ -0,0 +1,74 @@
+LOAD 'sqlol';
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+ id | val 
+----+-----
+(0 rows)
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+ ?column? 
+----------
+        3
+(1 row)
+
+-- test empty statement ignoring
+\;\;select 1 \g
+ ?column? 
+----------
+        1
+(1 row)
+
+-- check the created views
+\d
+       List of relations
+ Schema | Name | Type  | Owner 
+--------+------+-------+-------
+ public | t1   | table | rjuju
+ public | v0   | view  | rjuju
+ public | v1   | view  | rjuju
+ public | v2   | view  | rjuju
+ public | v3   | view  | rjuju
+ public | v4   | view  | rjuju
+ public | v5   | view  | rjuju
+(7 rows)
+
+--
+-- Error position
+--
+SELECT 1\;err;
+ERROR:  syntax error at or near "err"
+LINE 1: SELECT 1;err;
+                 ^
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+ERROR:  syntax error at or near "HAI"
+LINE 1: SELECT 1;HAI 1.2 I HAS A t1 GIMME id KTHXBYE
+                 ^
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+ERROR:  improper qualified name (too many dotted names): some.thing.public.t1
+LINE 1: SELECT 1;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHX...
+                                 ^
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
+ERROR:  relation "notatable" does not exist
+LINE 1: SELECT 1;SELECT * FROM notatable;
+                               ^
diff --git a/contrib/sqlol/repro.sql b/contrib/sqlol/repro.sql
new file mode 100644
index 0000000000..0ebcb53160
--- /dev/null
+++ b/contrib/sqlol/repro.sql
@@ -0,0 +1,18 @@
+DROP TABLE IF EXISTS t1 CASCADE;
+
+LOAD 'sqlol';
+
+\;\; SELECT 1\;
+
+CREATE TABLE t1 (id integer, val text);
+
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+SELECT 1\;SELECT 2\;SELECT 3 \g
+\d
diff --git a/contrib/sqlol/sql/01_sqlol.sql b/contrib/sqlol/sql/01_sqlol.sql
new file mode 100644
index 0000000000..918caf94c0
--- /dev/null
+++ b/contrib/sqlol/sql/01_sqlol.sql
@@ -0,0 +1,40 @@
+LOAD 'sqlol';
+
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+
+-- test empty statement ignoring
+\;\;select 1 \g
+
+-- check the created views
+\d
+
+--
+-- Error position
+--
+SELECT 1\;err;
+
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
index b986966181..7d4e1b631f 100644
--- a/contrib/sqlol/sqlol.c
+++ b/contrib/sqlol/sqlol.c
@@ -26,7 +26,8 @@ static parser_hook_type prev_parser_hook = NULL;
 void		_PG_init(void);
 void		_PG_fini(void);
 
-static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+static List *sqlol_parser_hook(const char *str, RawParseMode mode, int offset,
+							   bool *error);
 
 
 /*
@@ -54,23 +55,25 @@ _PG_fini(void)
  * sqlol_parser_hook: parse our grammar
  */
 static List *
-sqlol_parser_hook(const char *str, RawParseMode mode)
+sqlol_parser_hook(const char *str, RawParseMode mode, int offset, bool *error)
 {
 	sqlol_yyscan_t yyscanner;
 	sqlol_base_yy_extra_type yyextra;
 	int			yyresult;
 
-	if (mode != RAW_PARSE_DEFAULT)
+	if (mode != RAW_PARSE_DEFAULT && mode != RAW_PARSE_SINGLE_QUERY)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	/* initialize the flex scanner */
 	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
-							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords,
+							 offset);
 
 	/* initialize the bison parser */
 	sqlol_parser_init(&yyextra);
@@ -88,9 +91,10 @@ sqlol_parser_hook(const char *str, RawParseMode mode)
 	if (yyresult)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	return yyextra.parsetree;
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
index 64d00d14ca..4c36cfef5e 100644
--- a/contrib/sqlol/sqlol_gram.y
+++ b/contrib/sqlol/sqlol_gram.y
@@ -20,6 +20,7 @@
 
 #include "catalog/namespace.h"
 #include "nodes/makefuncs.h"
+#include "catalog/pg_class_d.h"
 
 #include "sqlol_gramparse.h"
 
@@ -106,10 +107,10 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
 	ResTarget			*target;
 }
 
-%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+%type <node>	stmt toplevel_stmt GimmehStmt MaekStmt simple_gimmeh columnref
 				indirection_el
 
-%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+%type <list>	parse_toplevel rawstmt gimmeh_list indirection
 
 %type <range>	qualified_name
 
@@ -134,22 +135,19 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
  */
 
 /* ordinary key words in alphabetical order */
-%token <keyword> A GIMMEH HAI HAS I KTHXBYE
-
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE MAEK
 
 %%
 
 /*
  *	The target production for the whole parse.
- *
- * Ordinarily we parse a list of statements, but if we see one of the
- * special MODE_XXX symbols as first token, we parse something else.
- * The options here correspond to enum RawParseMode, which see for details.
  */
 parse_toplevel:
-			stmtmulti
+			rawstmt
 			{
 				pg_yyget_extra(yyscanner)->parsetree = $1;
+
+				YYACCEPT;
 			}
 		;
 
@@ -163,24 +161,11 @@ parse_toplevel:
  * we'd get -1 for the location in such cases.
  * We also take care to discard empty statements entirely.
  */
-stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
-				{
-					if ($1 != NIL)
-					{
-						/* update length of previous stmt */
-						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
-					}
-					if ($3 != NULL)
-						$$ = lappend($1, makeRawStmt($3, @2 + 1));
-					else
-						$$ = $1;
-				}
-			| toplevel_stmt
+rawstmt:	toplevel_stmt KTHXBYE
 				{
-					if ($1 != NULL)
-						$$ = list_make1(makeRawStmt($1, 0));
-					else
-						$$ = NIL;
+					RawStmt *raw = makeRawStmt($1, 0);
+					updateRawStmtEnd(raw, @2 + 7);
+					$$ = list_make1(raw);
 				}
 		;
 
@@ -189,13 +174,12 @@ stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
  * those words have different meanings in function bodys.
  */
 toplevel_stmt:
-			stmt
+			HAI FCONST stmt { $$ = $3; }
 		;
 
 stmt:
 			GimmehStmt
-			| /*EMPTY*/
-				{ $$ = NULL; }
+			| MaekStmt
 		;
 
 /*****************************************************************************
@@ -209,12 +193,11 @@ GimmehStmt:
 		;
 
 simple_gimmeh:
-			HAI FCONST I HAS A qualified_name
-			GIMMEH gimmeh_list
+			I HAS A qualified_name GIMMEH gimmeh_list
 				{
 					SelectStmt *n = makeNode(SelectStmt);
-					n->targetList = $8;
-					n->fromClause = list_make1($6);
+					n->targetList = $6;
+					n->fromClause = list_make1($4);
 					$$ = (Node *)n;
 				}
 		;
@@ -233,6 +216,20 @@ gimmeh_el:
 				$$->location = @1;
 			}
 
+MaekStmt:
+		MAEK GimmehStmt A qualified_name
+			{
+				ViewStmt *n = makeNode(ViewStmt);
+				n->view = $4;
+				n->view->relpersistence = RELPERSISTENCE_PERMANENT;
+				n->aliases = NIL;
+				n->query = $2;
+				n->replace = false;
+				n->options = NIL;
+				n->withCheckOption = false;
+				$$ = (Node *) n;
+			}
+
 qualified_name:
 			ColId
 				{
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
index 2de3893ee4..8b50d88df9 100644
--- a/contrib/sqlol/sqlol_kwlist.h
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -19,3 +19,4 @@ PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
 PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
 PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
 PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
+PG_KEYWORD("maek", MAEK, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
index a7088b8390..e6d4d53446 100644
--- a/contrib/sqlol/sqlol_scan.l
+++ b/contrib/sqlol/sqlol_scan.l
@@ -412,8 +412,10 @@ sqlol_yyscan_t
 sqlol_scanner_init(const char *str,
 			 sqlol_yy_extra_type *yyext,
 			 const sqlol_ScanKeyword *keywords,
-			 int num_keywords)
+			 int num_keywords,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -432,13 +434,20 @@ sqlol_scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
index 0a497e9d91..57f95867ee 100644
--- a/contrib/sqlol/sqlol_scanner.h
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -108,7 +108,8 @@ extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
 extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
 								  sqlol_yy_extra_type *yyext,
 								  const sqlol_ScanKeyword *keywords,
-								  int num_keywords);
+								  int num_keywords,
+								  int offset);
 extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
 extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   sqlol_yyscan_t yyscanner);
-- 
2.31.1

From 3522fd2b0b27f52ab400abe1c9fbd5bb0c6169b4 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 22:47:18 +0800
Subject: [PATCH v3 1/4] Add a parser_hook hook.

This does nothing but allow third-party plugins to implement a different
syntax, and fallback on the core parser if they don't implement a superset of
the supported core syntax.
---
 src/backend/tcop/postgres.c | 16 ++++++++++++++--
 src/include/tcop/tcopprot.h |  5 +++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 8cea10c901..e941b59b85 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -99,6 +99,9 @@ int			log_statement = LOGSTMT_NONE;
 /* GUC variable for maximum stack depth (measured in kilobytes) */
 int			max_stack_depth = 100;
 
+/* Hook for plugins to get control in pg_parse_query() */
+parser_hook_type parser_hook = NULL;
+
 /* wait N seconds to allow attach from a debugger */
 int			PostAuthDelay = 0;
 
@@ -589,18 +592,27 @@ ProcessClientWriteInterrupt(bool blocked)
  * database tables.  So, we rely on the raw parser to determine whether
  * we've seen a COMMIT or ABORT command; when we are in abort state, other
  * commands are not processed any further than the raw parse stage.
+ *
+ * To support loadable plugins that monitor the parsing or implements SQL
+ * syntactic sugar we provide a hook variable that lets a plugin get control
+ * before and after the standard parsing process.  If the plugin only implement
+ * a subset of postgres supported syntax, it's its duty to call raw_parser (or
+ * the previous hook if any) for the statements it doesn't understand.
  */
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list;
+	List	   *raw_parsetree_list = NIL;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	if (parser_hook)
+		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
+	else
+		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 968345404e..131dc2b22e 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -17,6 +17,7 @@
 #include "nodes/params.h"
 #include "nodes/parsenodes.h"
 #include "nodes/plannodes.h"
+#include "parser/parser.h"
 #include "storage/procsignal.h"
 #include "utils/guc.h"
 #include "utils/queryenvironment.h"
@@ -43,6 +44,10 @@ typedef enum
 
 extern PGDLLIMPORT int log_statement;
 
+/* Hook for plugins to get control in pg_parse_query() */
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+extern PGDLLIMPORT parser_hook_type parser_hook;
+
 extern List *pg_parse_query(const char *query_string);
 extern List *pg_rewrite_query(Query *query);
 extern List *pg_analyze_and_rewrite(RawStmt *parsetree,
-- 
2.31.1

From 51a4fd99b8c66b970c3f8819cc135e1095126c48 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 23:54:02 +0800
Subject: [PATCH v3 2/4] Add a sqlol parser.

This is a toy example of alternative grammar that only accept a LOLCODE
compatible version of a

SELECT [column, ] column FROM tablename

and fallback on the core parser for everything else.
---
 contrib/Makefile                |   1 +
 contrib/sqlol/.gitignore        |   7 +
 contrib/sqlol/Makefile          |  33 ++
 contrib/sqlol/sqlol.c           | 107 +++++++
 contrib/sqlol/sqlol_gram.y      | 440 ++++++++++++++++++++++++++
 contrib/sqlol/sqlol_gramparse.h |  61 ++++
 contrib/sqlol/sqlol_keywords.c  |  98 ++++++
 contrib/sqlol/sqlol_keywords.h  |  38 +++
 contrib/sqlol/sqlol_kwlist.h    |  21 ++
 contrib/sqlol/sqlol_scan.l      | 544 ++++++++++++++++++++++++++++++++
 contrib/sqlol/sqlol_scanner.h   | 118 +++++++
 11 files changed, 1468 insertions(+)
 create mode 100644 contrib/sqlol/.gitignore
 create mode 100644 contrib/sqlol/Makefile
 create mode 100644 contrib/sqlol/sqlol.c
 create mode 100644 contrib/sqlol/sqlol_gram.y
 create mode 100644 contrib/sqlol/sqlol_gramparse.h
 create mode 100644 contrib/sqlol/sqlol_keywords.c
 create mode 100644 contrib/sqlol/sqlol_keywords.h
 create mode 100644 contrib/sqlol/sqlol_kwlist.h
 create mode 100644 contrib/sqlol/sqlol_scan.l
 create mode 100644 contrib/sqlol/sqlol_scanner.h

diff --git a/contrib/Makefile b/contrib/Makefile
index f27e458482..2a80cd137b 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -43,6 +43,7 @@ SUBDIRS = \
 		postgres_fdw	\
 		seg		\
 		spi		\
+		sqlol		\
 		tablefunc	\
 		tcn		\
 		test_decoding	\
diff --git a/contrib/sqlol/.gitignore b/contrib/sqlol/.gitignore
new file mode 100644
index 0000000000..3c4b587792
--- /dev/null
+++ b/contrib/sqlol/.gitignore
@@ -0,0 +1,7 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
+sqlol_gram.c
+sqlol_gram.h
+sqlol_scan.c
diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
new file mode 100644
index 0000000000..3850ac3fce
--- /dev/null
+++ b/contrib/sqlol/Makefile
@@ -0,0 +1,33 @@
+# contrib/sqlol/Makefile
+
+MODULE_big = sqlol
+OBJS = \
+	$(WIN32RES) \
+	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
+PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
+
+sqlol_gram.h: sqlol_gram.c
+	touch $@
+
+sqlol_gram.c: BISONFLAGS += -d
+# sqlol_gram.c: BISON_CHECK_CMD = $(PERL) $(srcdir)/check_keywords.pl $< $(top_srcdir)/src/include/parser/kwlist.h
+
+
+sqlol_scan.c: FLEXFLAGS = -CF -p -p
+sqlol_scan.c: FLEX_NO_BACKUP=yes
+sqlol_scan.c: FLEX_FIX_WARNING=yes
+
+
+# Force these dependencies to be known even without dependency info built:
+sqlol.o sqlol_gram.o sqlol_scan.o parser.o: sqlol_gram.h
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/sqlol
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
new file mode 100644
index 0000000000..b986966181
--- /dev/null
+++ b/contrib/sqlol/sqlol.c
@@ -0,0 +1,107 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol.c
+ *
+ *
+ * Copyright (c) 2008-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "tcop/tcopprot.h"
+
+#include "sqlol_gramparse.h"
+#include "sqlol_keywords.h"
+
+PG_MODULE_MAGIC;
+
+
+/* Saved hook values in case of unload */
+static parser_hook_type prev_parser_hook = NULL;
+
+void		_PG_init(void);
+void		_PG_fini(void);
+
+static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+
+
+/*
+ * Module load callback
+ */
+void
+_PG_init(void)
+{
+	/* Install hooks. */
+	prev_parser_hook = parser_hook;
+	parser_hook = sqlol_parser_hook;
+}
+
+/*
+ * Module unload callback
+ */
+void
+_PG_fini(void)
+{
+	/* Uninstall hooks. */
+	parser_hook = prev_parser_hook;
+}
+
+/*
+ * sqlol_parser_hook: parse our grammar
+ */
+static List *
+sqlol_parser_hook(const char *str, RawParseMode mode)
+{
+	sqlol_yyscan_t yyscanner;
+	sqlol_base_yy_extra_type yyextra;
+	int			yyresult;
+
+	if (mode != RAW_PARSE_DEFAULT)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	/* initialize the flex scanner */
+	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+
+	/* initialize the bison parser */
+	sqlol_parser_init(&yyextra);
+
+	/* Parse! */
+	yyresult = sqlol_base_yyparse(yyscanner);
+
+	/* Clean up (release memory) */
+	sqlol_scanner_finish(yyscanner);
+
+	/*
+	 * Invalid statement, fallback on previous parser_hook if any or
+	 * raw_parser()
+	 */
+	if (yyresult)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	return yyextra.parsetree;
+}
+
+int
+sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, sqlol_yyscan_t yyscanner)
+{
+	int			cur_token;
+
+	cur_token = sqlol_yylex(&(lvalp->sqlol_yystype), llocp, yyscanner);
+
+	return cur_token;
+}
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
new file mode 100644
index 0000000000..64d00d14ca
--- /dev/null
+++ b/contrib/sqlol/sqlol_gram.y
@@ -0,0 +1,440 @@
+%{
+
+/*#define YYDEBUG 1*/
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gram.y
+ *	  sqlol BISON rules/actions
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_gram.y
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "catalog/namespace.h"
+#include "nodes/makefuncs.h"
+
+#include "sqlol_gramparse.h"
+
+/*
+ * Location tracking support --- simpler than bison's default, since we only
+ * want to track the start position not the end position of each nonterminal.
+ */
+#define YYLLOC_DEFAULT(Current, Rhs, N) \
+	do { \
+		if ((N) > 0) \
+			(Current) = (Rhs)[1]; \
+		else \
+			(Current) = (-1); \
+	} while (0)
+
+/*
+ * The above macro assigns -1 (unknown) as the parse location of any
+ * nonterminal that was reduced from an empty rule, or whose leftmost
+ * component was reduced from an empty rule.  This is problematic
+ * for nonterminals defined like
+ *		OptFooList: / * EMPTY * / { ... } | OptFooList Foo { ... } ;
+ * because we'll set -1 as the location during the first reduction and then
+ * copy it during each subsequent reduction, leaving us with -1 for the
+ * location even when the list is not empty.  To fix that, do this in the
+ * action for the nonempty rule(s):
+ *		if (@$ < 0) @$ = @2;
+ * (Although we have many nonterminals that follow this pattern, we only
+ * bother with fixing @$ like this when the nonterminal's parse location
+ * is actually referenced in some rule.)
+ *
+ * A cleaner answer would be to make YYLLOC_DEFAULT scan all the Rhs
+ * locations until it's found one that's not -1.  Then we'd get a correct
+ * location for any nonterminal that isn't entirely empty.  But this way
+ * would add overhead to every rule reduction, and so far there's not been
+ * a compelling reason to pay that overhead.
+ */
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+
+#define parser_yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+#define parser_errposition(pos)  sqlol_scanner_errposition(pos, yyscanner)
+
+static void sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner,
+						 const char *msg);
+static RawStmt *makeRawStmt(Node *stmt, int stmt_location);
+static void updateRawStmtEnd(RawStmt *rs, int end_location);
+static Node *makeColumnRef(char *colname, List *indirection,
+						   int location, sqlol_yyscan_t yyscanner);
+static void check_qualified_name(List *names, sqlol_yyscan_t yyscanner);
+static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
+
+%}
+
+%pure-parser
+%expect 0
+%name-prefix="sqlol_base_yy"
+%locations
+
+%parse-param {sqlol_yyscan_t yyscanner}
+%lex-param   {sqlol_yyscan_t yyscanner}
+
+%union
+{
+	sqlol_YYSTYPE		sqlol_yystype;
+	/* these fields must match sqlol_YYSTYPE: */
+	int					ival;
+	char				*str;
+	const char			*keyword;
+
+	List				*list;
+	Node				*node;
+	Value				*value;
+	RangeVar			*range;
+	ResTarget			*target;
+}
+
+%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+				indirection_el
+
+%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+
+%type <range>	qualified_name
+
+%type <str>		ColId ColLabel attr_name
+
+%type <target>	gimmeh_el
+
+/*
+ * Non-keyword token types.  These are hard-wired into the "flex" lexer.
+ * They must be listed first so that their numeric codes do not depend on
+ * the set of keywords.  PL/pgSQL depends on this so that it can share the
+ * same lexer.  If you add/change tokens here, fix PL/pgSQL to match!
+ *
+ */
+%token <str>	IDENT FCONST SCONST Op
+
+/*
+ * If you want to make any keyword changes, update the keyword table in
+ * src/include/parser/kwlist.h and add new keywords to the appropriate one
+ * of the reserved-or-not-so-reserved keyword lists, below; search
+ * this file for "Keyword category lists".
+ */
+
+/* ordinary key words in alphabetical order */
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE
+
+
+%%
+
+/*
+ *	The target production for the whole parse.
+ *
+ * Ordinarily we parse a list of statements, but if we see one of the
+ * special MODE_XXX symbols as first token, we parse something else.
+ * The options here correspond to enum RawParseMode, which see for details.
+ */
+parse_toplevel:
+			stmtmulti
+			{
+				pg_yyget_extra(yyscanner)->parsetree = $1;
+			}
+		;
+
+/*
+ * At top level, we wrap each stmt with a RawStmt node carrying start location
+ * and length of the stmt's text.  Notice that the start loc/len are driven
+ * entirely from semicolon locations (@2).  It would seem natural to use
+ * @1 or @3 to get the true start location of a stmt, but that doesn't work
+ * for statements that can start with empty nonterminals (opt_with_clause is
+ * the main offender here); as noted in the comments for YYLLOC_DEFAULT,
+ * we'd get -1 for the location in such cases.
+ * We also take care to discard empty statements entirely.
+ */
+stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
+				{
+					if ($1 != NIL)
+					{
+						/* update length of previous stmt */
+						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
+					}
+					if ($3 != NULL)
+						$$ = lappend($1, makeRawStmt($3, @2 + 1));
+					else
+						$$ = $1;
+				}
+			| toplevel_stmt
+				{
+					if ($1 != NULL)
+						$$ = list_make1(makeRawStmt($1, 0));
+					else
+						$$ = NIL;
+				}
+		;
+
+/*
+ * toplevel_stmt includes BEGIN and END.  stmt does not include them, because
+ * those words have different meanings in function bodys.
+ */
+toplevel_stmt:
+			stmt
+		;
+
+stmt:
+			GimmehStmt
+			| /*EMPTY*/
+				{ $$ = NULL; }
+		;
+
+/*****************************************************************************
+ *
+ * GIMMEH statement
+ *
+ *****************************************************************************/
+
+GimmehStmt:
+			simple_gimmeh						{ $$ = $1; }
+		;
+
+simple_gimmeh:
+			HAI FCONST I HAS A qualified_name
+			GIMMEH gimmeh_list
+				{
+					SelectStmt *n = makeNode(SelectStmt);
+					n->targetList = $8;
+					n->fromClause = list_make1($6);
+					$$ = (Node *)n;
+				}
+		;
+
+gimmeh_list:
+		   gimmeh_el							{ $$ = list_make1($1); }
+		   | gimmeh_list ',' gimmeh_el			{ $$ = lappend($1, $3); }
+
+gimmeh_el:
+		 columnref
+			{
+				$$ = makeNode(ResTarget);
+				$$->name = NULL;
+				$$->indirection = NIL;
+				$$->val = (Node *)$1;
+				$$->location = @1;
+			}
+
+qualified_name:
+			ColId
+				{
+					$$ = makeRangeVar(NULL, $1, @1);
+				}
+			| ColId indirection
+				{
+					check_qualified_name($2, yyscanner);
+					$$ = makeRangeVar(NULL, NULL, @1);
+					switch (list_length($2))
+					{
+						case 1:
+							$$->catalogname = NULL;
+							$$->schemaname = $1;
+							$$->relname = strVal(linitial($2));
+							break;
+						case 2:
+							$$->catalogname = $1;
+							$$->schemaname = strVal(linitial($2));
+							$$->relname = strVal(lsecond($2));
+							break;
+						default:
+							/*
+							 * It's ok to error out here as at this point we
+							 * already parsed a "HAI FCONST" preamble, and no
+							 * other grammar is likely to accept a command
+							 * starting with that, so there's no point trying
+							 * to fall back on the other grammars.
+							 */
+							ereport(ERROR,
+									(errcode(ERRCODE_SYNTAX_ERROR),
+									 errmsg("improper qualified name (too many dotted names): %s",
+											NameListToString(lcons(makeString($1), $2))),
+									 parser_errposition(@1)));
+							break;
+					}
+				}
+		;
+
+columnref:	ColId
+				{
+					$$ = makeColumnRef($1, NIL, @1, yyscanner);
+				}
+			| ColId indirection
+				{
+					$$ = makeColumnRef($1, $2, @1, yyscanner);
+				}
+		;
+
+ColId:		IDENT									{ $$ = $1; }
+
+indirection:
+			indirection_el							{ $$ = list_make1($1); }
+			| indirection indirection_el			{ $$ = lappend($1, $2); }
+		;
+
+indirection_el:
+			'.' attr_name
+				{
+					$$ = (Node *) makeString($2);
+				}
+		;
+
+attr_name:	ColLabel								{ $$ = $1; };
+
+ColLabel:	IDENT									{ $$ = $1; }
+
+%%
+
+/*
+ * The signature of this function is required by bison.  However, we
+ * ignore the passed yylloc and instead use the last token position
+ * available from the scanner.
+ */
+static void
+sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner, const char *msg)
+{
+	parser_yyerror(msg);
+}
+
+static RawStmt *
+makeRawStmt(Node *stmt, int stmt_location)
+{
+	RawStmt    *rs = makeNode(RawStmt);
+
+	rs->stmt = stmt;
+	rs->stmt_location = stmt_location;
+	rs->stmt_len = 0;			/* might get changed later */
+	return rs;
+}
+
+/* Adjust a RawStmt to reflect that it doesn't run to the end of the string */
+static void
+updateRawStmtEnd(RawStmt *rs, int end_location)
+{
+	/*
+	 * If we already set the length, don't change it.  This is for situations
+	 * like "select foo ;; select bar" where the same statement will be last
+	 * in the string for more than one semicolon.
+	 */
+	if (rs->stmt_len > 0)
+		return;
+
+	/* OK, update length of RawStmt */
+	rs->stmt_len = end_location - rs->stmt_location;
+}
+
+static Node *
+makeColumnRef(char *colname, List *indirection,
+			  int location, sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * Generate a ColumnRef node, with an A_Indirection node added if there
+	 * is any subscripting in the specified indirection list.  However,
+	 * any field selection at the start of the indirection list must be
+	 * transposed into the "fields" part of the ColumnRef node.
+	 */
+	ColumnRef  *c = makeNode(ColumnRef);
+	int		nfields = 0;
+	ListCell *l;
+
+	c->location = location;
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Indices))
+		{
+			A_Indirection *i = makeNode(A_Indirection);
+
+			if (nfields == 0)
+			{
+				/* easy case - all indirection goes to A_Indirection */
+				c->fields = list_make1(makeString(colname));
+				i->indirection = check_indirection(indirection, yyscanner);
+			}
+			else
+			{
+				/* got to split the list in two */
+				i->indirection = check_indirection(list_copy_tail(indirection,
+																  nfields),
+												   yyscanner);
+				indirection = list_truncate(indirection, nfields);
+				c->fields = lcons(makeString(colname), indirection);
+			}
+			i->arg = (Node *) c;
+			return (Node *) i;
+		}
+		else if (IsA(lfirst(l), A_Star))
+		{
+			/* We only allow '*' at the end of a ColumnRef */
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+		nfields++;
+	}
+	/* No subscripting, so all indirection gets added to field list */
+	c->fields = lcons(makeString(colname), indirection);
+	return (Node *) c;
+}
+
+/* check_qualified_name --- check the result of qualified_name production
+ *
+ * It's easiest to let the grammar production for qualified_name allow
+ * subscripts and '*', which we then must reject here.
+ */
+static void
+check_qualified_name(List *names, sqlol_yyscan_t yyscanner)
+{
+	ListCell   *i;
+
+	foreach(i, names)
+	{
+		if (!IsA(lfirst(i), String))
+			parser_yyerror("syntax error");
+	}
+}
+
+/* check_indirection --- check the result of indirection production
+ *
+ * We only allow '*' at the end of the list, but it's hard to enforce that
+ * in the grammar, so do it here.
+ */
+static List *
+check_indirection(List *indirection, sqlol_yyscan_t yyscanner)
+{
+	ListCell *l;
+
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Star))
+		{
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+	}
+	return indirection;
+}
+
+/* sqlol_parser_init()
+ * Initialize to parse one query string
+ */
+void
+sqlol_parser_init(sqlol_base_yy_extra_type *yyext)
+{
+	yyext->parsetree = NIL;		/* in case grammar forgets to set it */
+}
diff --git a/contrib/sqlol/sqlol_gramparse.h b/contrib/sqlol/sqlol_gramparse.h
new file mode 100644
index 0000000000..58233a8d87
--- /dev/null
+++ b/contrib/sqlol/sqlol_gramparse.h
@@ -0,0 +1,61 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gramparse.h
+ *		Shared definitions for the "raw" parser (flex and bison phases only)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_gramparse.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_GRAMPARSE_H
+#define SQLOL_GRAMPARSE_H
+
+#include "nodes/parsenodes.h"
+#include "sqlol_scanner.h"
+
+/*
+ * NB: include gram.h only AFTER including scanner.h, because scanner.h
+ * is what #defines YYLTYPE.
+ */
+#include "sqlol_gram.h"
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.  Private
+ * state needed for raw parsing/lexing goes here.
+ */
+typedef struct sqlol_base_yy_extra_type
+{
+	/*
+	 * Fields used by the core scanner.
+	 */
+	sqlol_yy_extra_type sqlol_yy_extra;
+
+	/*
+	 * State variables that belong to the grammar.
+	 */
+	List	   *parsetree;		/* final parse result is delivered here */
+} sqlol_base_yy_extra_type;
+
+/*
+ * In principle we should use yyget_extra() to fetch the yyextra field
+ * from a yyscanner struct.  However, flex always puts that field first,
+ * and this is sufficiently performance-critical to make it seem worth
+ * cheating a bit to use an inline macro.
+ */
+#define pg_yyget_extra(yyscanner) (*((sqlol_base_yy_extra_type **) (yyscanner)))
+
+
+/* from parser.c */
+extern int	sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+
+/* from gram.y */
+extern void sqlol_parser_init(sqlol_base_yy_extra_type *yyext);
+extern int	sqlol_baseyyparse(sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_GRAMPARSE_H */
diff --git a/contrib/sqlol/sqlol_keywords.c b/contrib/sqlol/sqlol_keywords.c
new file mode 100644
index 0000000000..dbbdf5493c
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.c
@@ -0,0 +1,98 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.c
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  sqlol/sqlol_keywords.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "sqlol_gramparse.h"
+
+#define PG_KEYWORD(a,b,c) {a,b,c},
+
+const sqlol_ScanKeyword sqlol_ScanKeywords[] = {
+#include "sqlol_kwlist.h"
+};
+
+const int	sqlol_NumScanKeywords = lengthof(sqlol_ScanKeywords);
+
+#undef PG_KEYWORD
+
+
+/*
+ * ScanKeywordLookup - see if a given word is a keyword
+ *
+ * The table to be searched is passed explicitly, so that this can be used
+ * to search keyword lists other than the standard list appearing above.
+ *
+ * Returns a pointer to the sqlol_ScanKeyword table entry, or NULL if no match.
+ *
+ * The match is done case-insensitively.  Note that we deliberately use a
+ * dumbed-down case conversion that will only translate 'A'-'Z' into 'a'-'z',
+ * even if we are in a locale where tolower() would produce more or different
+ * translations.  This is to conform to the SQL99 spec, which says that
+ * keywords are to be matched in this way even though non-keyword identifiers
+ * receive a different case-normalization mapping.
+ */
+const sqlol_ScanKeyword *
+sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords)
+{
+	int			len,
+				i;
+	char		word[NAMEDATALEN];
+	const sqlol_ScanKeyword *low;
+	const sqlol_ScanKeyword *high;
+
+	len = strlen(text);
+	/* We assume all keywords are shorter than NAMEDATALEN. */
+	if (len >= NAMEDATALEN)
+		return NULL;
+
+	/*
+	 * Apply an ASCII-only downcasing.  We must not use tolower() since it may
+	 * produce the wrong translation in some locales (eg, Turkish).
+	 */
+	for (i = 0; i < len; i++)
+	{
+		char		ch = text[i];
+
+		if (ch >= 'A' && ch <= 'Z')
+			ch += 'a' - 'A';
+		word[i] = ch;
+	}
+	word[len] = '\0';
+
+	/*
+	 * Now do a binary search using plain strcmp() comparison.
+	 */
+	low = keywords;
+	high = keywords + (num_keywords - 1);
+	while (low <= high)
+	{
+		const sqlol_ScanKeyword *middle;
+		int			difference;
+
+		middle = low + (high - low) / 2;
+		difference = strcmp(middle->name, word);
+		if (difference == 0)
+			return middle;
+		else if (difference < 0)
+			low = middle + 1;
+		else
+			high = middle - 1;
+	}
+
+	return NULL;
+}
+
diff --git a/contrib/sqlol/sqlol_keywords.h b/contrib/sqlol/sqlol_keywords.h
new file mode 100644
index 0000000000..bc4acf4541
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.h
@@ -0,0 +1,38 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.h
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_keywords.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SQLOL_KEYWORDS_H
+#define SQLOL_KEYWORDS_H
+
+/* Keyword categories --- should match lists in gram.y */
+#define UNRESERVED_KEYWORD		0
+#define COL_NAME_KEYWORD		1
+#define TYPE_FUNC_NAME_KEYWORD	2
+#define RESERVED_KEYWORD		3
+
+
+typedef struct sqlol_ScanKeyword
+{
+	const char *name;			/* in lower case */
+	int16		value;			/* grammar's token code */
+	int16		category;		/* see codes above */
+} sqlol_ScanKeyword;
+
+extern PGDLLIMPORT const sqlol_ScanKeyword sqlol_ScanKeywords[];
+extern PGDLLIMPORT const int sqlol_NumScanKeywords;
+
+extern const sqlol_ScanKeyword *sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords);
+
+#endif							/* SQLOL_KEYWORDS_H */
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
new file mode 100644
index 0000000000..2de3893ee4
--- /dev/null
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -0,0 +1,21 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_kwlist.h
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_kwlist.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* name, value, category, is-bare-label */
+PG_KEYWORD("a", A, UNRESERVED_KEYWORD)
+PG_KEYWORD("gimmeh", GIMMEH, UNRESERVED_KEYWORD)
+PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
+PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
+PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
+PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
new file mode 100644
index 0000000000..a7088b8390
--- /dev/null
+++ b/contrib/sqlol/sqlol_scan.l
@@ -0,0 +1,544 @@
+%top{
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scan.l
+ *	  lexical scanner for sqlol
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_scan.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "common/string.h"
+#include "sqlol_gramparse.h"
+#include "parser/scansup.h"
+#include "mb/pg_wchar.h"
+
+#include "sqlol_keywords.h"
+}
+
+%{
+
+/* LCOV_EXCL_START */
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+
+/*
+ * Set the type of YYSTYPE.
+ */
+#define YYSTYPE sqlol_YYSTYPE
+
+/*
+ * Set the type of yyextra.  All state variables used by the scanner should
+ * be in yyextra, *not* statically allocated.
+ */
+#define YY_EXTRA_TYPE sqlol_yy_extra_type *
+
+/*
+ * Each call to yylex must set yylloc to the location of the found token
+ * (expressed as a byte offset from the start of the input text).
+ * When we parse a token that requires multiple lexer rules to process,
+ * this should be done in the first such rule, else yylloc will point
+ * into the middle of the token.
+ */
+#define SET_YYLLOC()  (*(yylloc) = yytext - yyextra->scanbuf)
+
+/*
+ * Advance yylloc by the given number of bytes.
+ */
+#define ADVANCE_YYLLOC(delta)  ( *(yylloc) += (delta) )
+
+/*
+ * Sometimes, we do want yylloc to point into the middle of a token; this is
+ * useful for instance to throw an error about an escape sequence within a
+ * string literal.  But if we find no error there, we want to revert yylloc
+ * to the token start, so that that's the location reported to the parser.
+ * Use PUSH_YYLLOC/POP_YYLLOC to save/restore yylloc around such code.
+ * (Currently the implied "stack" is just one location, but someday we might
+ * need to nest these.)
+ */
+#define PUSH_YYLLOC()	(yyextra->save_yylloc = *(yylloc))
+#define POP_YYLLOC()	(*(yylloc) = yyextra->save_yylloc)
+
+#define startlit()	( yyextra->literallen = 0 )
+static void addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner);
+static void addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner);
+static char *litbufdup(sqlol_yyscan_t yyscanner);
+
+#define yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+
+#define lexer_errposition()  sqlol_scanner_errposition(*(yylloc), yyscanner)
+
+/*
+ * Work around a bug in flex 2.5.35: it emits a couple of functions that
+ * it forgets to emit declarations for.  Since we use -Wmissing-prototypes,
+ * this would cause warnings.  Providing our own declarations should be
+ * harmless even when the bug gets fixed.
+ */
+extern int	sqlol_yyget_column(yyscan_t yyscanner);
+extern void sqlol_yyset_column(int column_no, yyscan_t yyscanner);
+
+%}
+
+%option reentrant
+%option bison-bridge
+%option bison-locations
+%option 8bit
+%option never-interactive
+%option nodefault
+%option noinput
+%option nounput
+%option noyywrap
+%option noyyalloc
+%option noyyrealloc
+%option noyyfree
+%option warn
+%option prefix="sqlol_yy"
+
+/*
+ * OK, here is a short description of lex/flex rules behavior.
+ * The longest pattern which matches an input string is always chosen.
+ * For equal-length patterns, the first occurring in the rules list is chosen.
+ * INITIAL is the starting state, to which all non-conditional rules apply.
+ * Exclusive states change parsing rules while the state is active.  When in
+ * an exclusive state, only those rules defined for that state apply.
+ *
+ * We use exclusive states for quoted strings, extended comments,
+ * and to eliminate parsing troubles for numeric strings.
+ * Exclusive states:
+ *  <xd> delimited identifiers (double-quoted identifiers)
+ *  <xq> standard quoted strings
+ *  <xqs> quote stop (detect continued strings)
+ *
+ * Remember to add an <<EOF>> case whenever you add a new exclusive state!
+ * The default one is probably not the right thing.
+ */
+
+%x xd
+%x xq
+%x xqs
+
+/*
+ * In order to make the world safe for Windows and Mac clients as well as
+ * Unix ones, we accept either \n or \r as a newline.  A DOS-style \r\n
+ * sequence will be seen as two successive newlines, but that doesn't cause
+ * any problems.  Comments that start with -- and extend to the next
+ * newline are treated as equivalent to a single whitespace character.
+ *
+ * NOTE a fine point: if there is no newline following --, we will absorb
+ * everything to the end of the input as a comment.  This is correct.  Older
+ * versions of Postgres failed to recognize -- as a comment if the input
+ * did not end with a newline.
+ *
+ * XXX perhaps \f (formfeed) should be treated as a newline as well?
+ *
+ * XXX if you change the set of whitespace characters, fix scanner_isspace()
+ * to agree.
+ */
+
+space			[ \t\n\r\f]
+horiz_space		[ \t\f]
+newline			[\n\r]
+non_newline		[^\n\r]
+
+comment			("--"{non_newline}*)
+
+whitespace		({space}+|{comment})
+
+/*
+ * SQL requires at least one newline in the whitespace separating
+ * string literals that are to be concatenated.  Silly, but who are we
+ * to argue?  Note that {whitespace_with_newline} should not have * after
+ * it, whereas {whitespace} should generally have a * after it...
+ */
+
+special_whitespace		({space}+|{comment}{newline})
+horiz_whitespace		({horiz_space}|{comment})
+whitespace_with_newline	({horiz_whitespace}*{newline}{special_whitespace}*)
+
+quote			'
+/* If we see {quote} then {quotecontinue}, the quoted string continues */
+quotecontinue	{whitespace_with_newline}{quote}
+
+/*
+ * {quotecontinuefail} is needed to avoid lexer backup when we fail to match
+ * {quotecontinue}.  It might seem that this could just be {whitespace}*,
+ * but if there's a dash after {whitespace_with_newline}, it must be consumed
+ * to see if there's another dash --- which would start a {comment} and thus
+ * allow continuation of the {quotecontinue} token.
+ */
+quotecontinuefail	{whitespace}*"-"?
+
+/* Extended quote
+ * xqdouble implements embedded quote, ''''
+ */
+xqstart			{quote}
+xqdouble		{quote}{quote}
+xqinside		[^']+
+
+/* Double quote
+ * Allows embedded spaces and other special characters into identifiers.
+ */
+dquote			\"
+xdstart			{dquote}
+xdstop			{dquote}
+xddouble		{dquote}{dquote}
+xdinside		[^"]+
+
+digit			[0-9]
+ident_start		[A-Za-z\200-\377_]
+ident_cont		[A-Za-z\200-\377_0-9\$]
+
+identifier		{ident_start}{ident_cont}*
+
+decimal			(({digit}+)|({digit}*\.{digit}+)|({digit}+\.{digit}*))
+
+other			.
+
+%%
+
+{whitespace}	{
+					/* ignore */
+				}
+
+
+{xqstart}		{
+					yyextra->saw_non_ascii = false;
+					SET_YYLLOC();
+					BEGIN(xq);
+					startlit();
+}
+<xq>{quote} {
+					/*
+					 * When we are scanning a quoted string and see an end
+					 * quote, we must look ahead for a possible continuation.
+					 * If we don't see one, we know the end quote was in fact
+					 * the end of the string.  To reduce the lexer table size,
+					 * we use a single "xqs" state to do the lookahead for all
+					 * types of strings.
+					 */
+					yyextra->state_before_str_stop = YYSTATE;
+					BEGIN(xqs);
+				}
+<xqs>{quotecontinue} {
+					/*
+					 * Found a quote continuation, so return to the in-quote
+					 * state and continue scanning the literal.  Nothing is
+					 * added to the literal's contents.
+					 */
+					BEGIN(yyextra->state_before_str_stop);
+				}
+<xqs>{quotecontinuefail} |
+<xqs>{other} |
+<xqs><<EOF>>	{
+					/*
+					 * Failed to see a quote continuation.  Throw back
+					 * everything after the end quote, and handle the string
+					 * according to the state we were in previously.
+					 */
+					yyless(0);
+					BEGIN(INITIAL);
+
+					switch (yyextra->state_before_str_stop)
+					{
+						case xq:
+							/*
+							 * Check that the data remains valid, if it might
+							 * have been made invalid by unescaping any chars.
+							 */
+							if (yyextra->saw_non_ascii)
+								pg_verifymbstr(yyextra->literalbuf,
+										yyextra->literallen,
+										false);
+							yylval->str = litbufdup(yyscanner);
+							return SCONST;
+						default:
+							yyerror("unhandled previous state in xqs");
+					}
+				}
+
+<xq>{xqdouble} {
+					addlitchar('\'', yyscanner);
+				}
+<xq>{xqinside}  {
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xq><<EOF>>		{ yyerror("unterminated quoted string"); }
+
+
+{xdstart}		{
+					SET_YYLLOC();
+					BEGIN(xd);
+					startlit();
+				}
+<xd>{xdstop}	{
+					char	   *ident;
+
+					BEGIN(INITIAL);
+					if (yyextra->literallen == 0)
+						yyerror("zero-length delimited identifier");
+					ident = litbufdup(yyscanner);
+					if (yyextra->literallen >= NAMEDATALEN)
+						truncate_identifier(ident, yyextra->literallen, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+<xd>{xddouble}	{
+					addlitchar('"', yyscanner);
+				}
+<xd>{xdinside}	{
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xd><<EOF>>		{ yyerror("unterminated quoted identifier"); }
+
+{decimal}		{
+					SET_YYLLOC();
+					yylval->str = pstrdup(yytext);
+					return FCONST;
+				}
+
+{identifier}	{
+					const sqlol_ScanKeyword *keyword;
+					char	   *ident;
+
+					SET_YYLLOC();
+
+					/* Is it a keyword? */
+					keyword = sqlol_ScanKeywordLookup(yytext,
+													yyextra->keywords,
+													yyextra->num_keywords);
+					if (keyword != NULL)
+					{
+						yylval->keyword = keyword->name;
+						return keyword->value;
+					}
+
+					/*
+					 * No.  Convert the identifier to lower case, and truncate
+					 * if necessary.
+					 */
+					ident = downcase_truncate_identifier(yytext, yyleng, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+
+{other}			{
+					SET_YYLLOC();
+					return yytext[0];
+				}
+
+<<EOF>>			{
+					SET_YYLLOC();
+					yyterminate();
+				}
+
+%%
+
+/* LCOV_EXCL_STOP */
+
+/*
+ * Arrange access to yyextra for subroutines of the main yylex() function.
+ * We expect each subroutine to have a yyscanner parameter.  Rather than
+ * use the yyget_xxx functions, which might or might not get inlined by the
+ * compiler, we cheat just a bit and cast yyscanner to the right type.
+ */
+#undef yyextra
+#define yyextra  (((struct yyguts_t *) yyscanner)->yyextra_r)
+
+/* Likewise for a couple of other things we need. */
+#undef yylloc
+#define yylloc	(((struct yyguts_t *) yyscanner)->yylloc_r)
+#undef yyleng
+#define yyleng	(((struct yyguts_t *) yyscanner)->yyleng_r)
+
+
+/*
+ * scanner_errposition
+ *		Report a lexer or grammar error cursor position, if possible.
+ *
+ * This is expected to be used within an ereport() call.  The return value
+ * is a dummy (always 0, in fact).
+ *
+ * Note that this can only be used for messages emitted during raw parsing
+ * (essentially, sqlol_scan.l, sqlol_parser.c, sqlol_and gram.y), since it
+ * requires the yyscanner struct to still be available.
+ */
+int
+sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner)
+{
+	int			pos;
+
+	if (location < 0)
+		return 0;				/* no-op if location is unknown */
+
+	/* Convert byte offset to character number */
+	pos = pg_mbstrlen_with_len(yyextra->scanbuf, location) + 1;
+	/* And pass it to the ereport mechanism */
+	return errposition(pos);
+}
+
+/*
+ * scanner_yyerror
+ *		Report a lexer or grammar error.
+ *
+ * Just ignore as we'll fallback to raw_parser().
+ */
+void
+sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner)
+{
+	return;
+}
+
+
+/*
+ * Called before any actual parsing is done
+ */
+sqlol_yyscan_t
+sqlol_scanner_init(const char *str,
+			 sqlol_yy_extra_type *yyext,
+			 const sqlol_ScanKeyword *keywords,
+			 int num_keywords)
+{
+	Size		slen = strlen(str);
+	yyscan_t	scanner;
+
+	if (yylex_init(&scanner) != 0)
+		elog(ERROR, "yylex_init() failed: %m");
+
+	sqlol_yyset_extra(yyext, scanner);
+
+	yyext->keywords = keywords;
+	yyext->num_keywords = num_keywords;
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	yyext->scanbuf = (char *) palloc(slen + 2);
+	yyext->scanbuflen = slen;
+	memcpy(yyext->scanbuf, str, slen);
+	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+
+	/* initialize literal buffer to a reasonable but expansible size */
+	yyext->literalalloc = 1024;
+	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
+	yyext->literallen = 0;
+
+	return scanner;
+}
+
+
+/*
+ * Called after parsing is done to clean up after scanner_init()
+ */
+void
+sqlol_scanner_finish(sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * We don't bother to call yylex_destroy(), because all it would do is
+	 * pfree a small amount of control storage.  It's cheaper to leak the
+	 * storage until the parsing context is destroyed.  The amount of space
+	 * involved is usually negligible compared to the output parse tree
+	 * anyway.
+	 *
+	 * We do bother to pfree the scanbuf and literal buffer, but only if they
+	 * represent a nontrivial amount of space.  The 8K cutoff is arbitrary.
+	 */
+	if (yyextra->scanbuflen >= 8192)
+		pfree(yyextra->scanbuf);
+	if (yyextra->literalalloc >= 8192)
+		pfree(yyextra->literalbuf);
+}
+
+
+static void
+addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + yleng) >= yyextra->literalalloc)
+	{
+		do
+		{
+			yyextra->literalalloc *= 2;
+		} while ((yyextra->literallen + yleng) >= yyextra->literalalloc);
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	memcpy(yyextra->literalbuf + yyextra->literallen, ytext, yleng);
+	yyextra->literallen += yleng;
+}
+
+
+static void
+addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + 1) >= yyextra->literalalloc)
+	{
+		yyextra->literalalloc *= 2;
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	yyextra->literalbuf[yyextra->literallen] = ychar;
+	yyextra->literallen += 1;
+}
+
+
+/*
+ * Create a palloc'd copy of literalbuf, adding a trailing null.
+ */
+static char *
+litbufdup(sqlol_yyscan_t yyscanner)
+{
+	int			llen = yyextra->literallen;
+	char	   *new;
+
+	new = palloc(llen + 1);
+	memcpy(new, yyextra->literalbuf, llen);
+	new[llen] = '\0';
+	return new;
+}
+
+/*
+ * Interface functions to make flex use palloc() instead of malloc().
+ * It'd be better to make these static, but flex insists otherwise.
+ */
+
+void *
+sqlol_yyalloc(yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	return palloc(bytes);
+}
+
+void *
+sqlol_yyrealloc(void *ptr, yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		return repalloc(ptr, bytes);
+	else
+		return palloc(bytes);
+}
+
+void
+sqlol_yyfree(void *ptr, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		pfree(ptr);
+}
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
new file mode 100644
index 0000000000..0a497e9d91
--- /dev/null
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -0,0 +1,118 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scanner.h
+ *		API for the core scanner (flex machine)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_scanner.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_SCANNER_H
+#define SQLOL_SCANNER_H
+
+#include "sqlol_keywords.h"
+
+/*
+ * The scanner returns extra data about scanned tokens in this union type.
+ * Note that this is a subset of the fields used in YYSTYPE of the bison
+ * parsers built atop the scanner.
+ */
+typedef union sqlol_YYSTYPE
+{
+	int			ival;			/* for integer literals */
+	char	   *str;			/* for identifiers and non-integer literals */
+	const char *keyword;		/* canonical spelling of keywords */
+} sqlol_YYSTYPE;
+
+/*
+ * We track token locations in terms of byte offsets from the start of the
+ * source string, not the column number/line number representation that
+ * bison uses by default.  Also, to minimize overhead we track only one
+ * location (usually the first token location) for each construct, not
+ * the beginning and ending locations as bison does by default.  It's
+ * therefore sufficient to make YYLTYPE an int.
+ */
+#define YYLTYPE  int
+
+/*
+ * Another important component of the scanner's API is the token code numbers.
+ * However, those are not defined in this file, because bison insists on
+ * defining them for itself.  The token codes used by the core scanner are
+ * the ASCII characters plus these:
+ *	%token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
+ *	%token <ival>	ICONST PARAM
+ *	%token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
+ *	%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+ * The above token definitions *must* be the first ones declared in any
+ * bison parser built atop this scanner, so that they will have consistent
+ * numbers assigned to them (specifically, IDENT = 258 and so on).
+ */
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.
+ * Private state needed by the core scanner goes here.  Note that the actual
+ * yy_extra struct may be larger and have this as its first component, thus
+ * allowing the calling parser to keep some fields of its own in YY_EXTRA.
+ */
+typedef struct sqlol_yy_extra_type
+{
+	/*
+	 * The string the scanner is physically scanning.  We keep this mainly so
+	 * that we can cheaply compute the offset of the current token (yytext).
+	 */
+	char	   *scanbuf;
+	Size		scanbuflen;
+
+	/*
+	 * The keyword list to use, and the associated grammar token codes.
+	 */
+	const sqlol_ScanKeyword *keywords;
+	int		num_keywords;
+
+	/*
+	 * literalbuf is used to accumulate literal values when multiple rules are
+	 * needed to parse a single literal.  Call startlit() to reset buffer to
+	 * empty, addlit() to add text.  NOTE: the string in literalbuf is NOT
+	 * necessarily null-terminated, but there always IS room to add a trailing
+	 * null at offset literallen.  We store a null only when we need it.
+	 */
+	char	   *literalbuf;		/* palloc'd expandable buffer */
+	int			literallen;		/* actual current string length */
+	int			literalalloc;	/* current allocated buffer size */
+
+	/*
+	 * Random assorted scanner state.
+	 */
+	int			state_before_str_stop;	/* start cond. before end quote */
+	YYLTYPE		save_yylloc;	/* one-element stack for PUSH_YYLLOC() */
+
+	/* state variables for literal-lexing warnings */
+	bool		saw_non_ascii;
+} sqlol_yy_extra_type;
+
+/*
+ * The type of yyscanner is opaque outside scan.l.
+ */
+typedef void *sqlol_yyscan_t;
+
+
+/* Constant data exported from parser/scan.l */
+extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
+
+/* Entry points in parser/scan.l */
+extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
+								  sqlol_yy_extra_type *yyext,
+								  const sqlol_ScanKeyword *keywords,
+								  int num_keywords);
+extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
+extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+extern int	sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner);
+extern void sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_SCANNER_H */
-- 
2.31.1

From e85972610aa0d3aa090011c7f2c3bbe976a7c803 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 01:33:42 +0800
Subject: [PATCH v3 3/4] Add a new MODE_SINGLE_QUERY to the core parser and use
 it in pg_parse_query.

If a third-party module provides a parser_hook, pg_parse_query() switches to
single-query parsing so multi-query commands using different grammar can work
properly.  If the third-party module supports the full set of SQL we support,
or want to prevent fallback on the core parser, it can ignore the
MODE_SINGLE_QUERY mode and parse the full query string.  In that case they must
return a List with more than one RawStmt or a single RawStmt with a 0 length to
stop the parsing phase, or raise an ERROR.

Otherwise, plugins should parse a single query only and always return a List
containing a single RawStmt with a properly set length (possibly 0 if it was a
single query without end of query delimiter).  If the command is valid but
doesn't contain any statements (e.g. a single semi-colon), a single RawStmt
with a NULL stmt field should be returned, containing the consumed query string
length so we can move to the next command in a single pass rather than 1 byte
at a time.

Also, third-party modules can choose to ignore some or all of parsing error if
they want to implement only subset of postgres suppoted syntax, or even a
totally different syntax, and fall-back on core grammar for unhandled case.  In
thase case, they should set the error flag to true.  The returned List will be
ignored and the same offset of the input string will be parsed using the core
parser.

Finally, note that third-party plugins that wants to fallback on other grammar
should first try to call a previous parser hook if any before setting the error
switch and returning.
---
 .../pg_stat_statements/pg_stat_statements.c   |   3 +-
 src/backend/commands/tablecmds.c              |   2 +-
 src/backend/executor/spi.c                    |   4 +-
 src/backend/parser/gram.y                     |  29 +++-
 src/backend/parser/parse_type.c               |   2 +-
 src/backend/parser/parser.c                   |  15 +-
 src/backend/parser/scan.l                     |  26 +++-
 src/backend/tcop/postgres.c                   | 138 ++++++++++++++++--
 src/include/parser/parser.h                   |   5 +-
 src/include/parser/scanner.h                  |   6 +-
 src/include/tcop/tcopprot.h                   |   3 +-
 src/pl/plpgsql/src/pl_gram.y                  |   2 +-
 src/pl/plpgsql/src/pl_scanner.c               |   2 +-
 13 files changed, 210 insertions(+), 27 deletions(-)

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 09433c8c96..d852575613 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -2718,7 +2718,8 @@ fill_in_constant_lengths(JumbleState *jstate, const char *query,
 	yyscanner = scanner_init(query,
 							 &yyextra,
 							 &ScanKeywords,
-							 ScanKeywordTokens);
+							 ScanKeywordTokens,
+							 0);
 
 	/* we don't want to re-emit any escape string warnings */
 	yyextra.escape_string_warning = false;
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 028e8ac46b..284933c693 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -12677,7 +12677,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 	 * parse_analyze() or the rewriter, but instead we need to pass them
 	 * through parse_utilcmd.c to make them ready for execution.
 	 */
-	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT);
+	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT, 0);
 	querytree_list = NIL;
 	foreach(list_item, raw_parsetree_list)
 	{
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index b8bd05e894..f05b3ce9e7 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -2120,7 +2120,7 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Do parse analysis and rule rewrite for each raw parsetree, storing the
@@ -2228,7 +2228,7 @@ _SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Construct plancache entries, but don't do parse analysis yet.
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 9ee90e3f13..2cac062ef4 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -626,7 +626,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
 %token <ival>	ICONST PARAM
 %token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
-%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS END_OF_FILE
 
 /*
  * If you want to make any keyword changes, update the keyword table in
@@ -753,6 +753,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token		MODE_PLPGSQL_ASSIGN1
 %token		MODE_PLPGSQL_ASSIGN2
 %token		MODE_PLPGSQL_ASSIGN3
+%token		MODE_SINGLE_QUERY
 
 
 /* Precedence: lowest to highest */
@@ -858,6 +859,32 @@ parse_toplevel:
 				pg_yyget_extra(yyscanner)->parsetree =
 					list_make1(makeRawStmt((Node *) n, 0));
 			}
+			| MODE_SINGLE_QUERY toplevel_stmt ';'
+			{
+				RawStmt *raw = makeRawStmt($2, 0);
+				updateRawStmtEnd(raw, @3 + 1);
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string and move to the next command.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(raw);
+				YYACCEPT;
+			}
+			/*
+			 * We need to explicitly look for EOF to parse non-semicolon
+			 * terminated statements in single query mode, as we could
+			 * otherwise successfully parse the beginning of an otherwise
+			 * invalid query.
+			 */
+			| MODE_SINGLE_QUERY toplevel_stmt END_OF_FILE
+			{
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(makeRawStmt($2, 0));
+				YYACCEPT;
+			}
 		;
 
 /*
diff --git a/src/backend/parser/parse_type.c b/src/backend/parser/parse_type.c
index abe131ebeb..e9a7b5d62a 100644
--- a/src/backend/parser/parse_type.c
+++ b/src/backend/parser/parse_type.c
@@ -746,7 +746,7 @@ typeStringToTypeName(const char *str)
 	ptserrcontext.previous = error_context_stack;
 	error_context_stack = &ptserrcontext;
 
-	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME);
+	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME, 0);
 
 	error_context_stack = ptserrcontext.previous;
 
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index 875de7ba28..23fd49e74c 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -37,17 +37,25 @@ static char *str_udeescape(const char *str, char escape,
  *
  * Returns a list of raw (un-analyzed) parse trees.  The contents of the
  * list have the form required by the specified RawParseMode.
+ *
+ * For all mode different from MODE_SINGLE_QUERY, caller should provide a 0
+ * offset as the whole input string should be parsed.  Otherwise, caller should
+ * provide the wanted offset in the input string, or -1 if no offset is
+ * required.
  */
 List *
-raw_parser(const char *str, RawParseMode mode)
+raw_parser(const char *str, RawParseMode mode, int offset)
 {
 	core_yyscan_t yyscanner;
 	base_yy_extra_type yyextra;
 	int			yyresult;
 
+	Assert((mode != RAW_PARSE_SINGLE_QUERY && offset == 0) ||
+			(mode == RAW_PARSE_SINGLE_QUERY && offset != 0));
+
 	/* initialize the flex scanner */
 	yyscanner = scanner_init(str, &yyextra.core_yy_extra,
-							 &ScanKeywords, ScanKeywordTokens);
+							 &ScanKeywords, ScanKeywordTokens, offset);
 
 	/* base_yylex() only needs us to initialize the lookahead token, if any */
 	if (mode == RAW_PARSE_DEFAULT)
@@ -61,7 +69,8 @@ raw_parser(const char *str, RawParseMode mode)
 			MODE_PLPGSQL_EXPR,	/* RAW_PARSE_PLPGSQL_EXPR */
 			MODE_PLPGSQL_ASSIGN1,	/* RAW_PARSE_PLPGSQL_ASSIGN1 */
 			MODE_PLPGSQL_ASSIGN2,	/* RAW_PARSE_PLPGSQL_ASSIGN2 */
-			MODE_PLPGSQL_ASSIGN3	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_PLPGSQL_ASSIGN3,	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_SINGLE_QUERY		/* RAW_PARSE_SINGLE_QUERY */
 		};
 
 		yyextra.have_lookahead = true;
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
index 9f9d8a1706..8ccbe95ac6 100644
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -1041,7 +1041,10 @@ other			.
 
 <<EOF>>			{
 					SET_YYLLOC();
-					yyterminate();
+					if (yyextra->return_eof)
+						return END_OF_FILE;
+					else
+						yyterminate();
 				}
 
 %%
@@ -1189,8 +1192,10 @@ core_yyscan_t
 scanner_init(const char *str,
 			 core_yy_extra_type *yyext,
 			 const ScanKeywordList *keywordlist,
-			 const uint16 *keyword_tokens)
+			 const uint16 *keyword_tokens,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -1213,13 +1218,28 @@ scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Note that pg_parse_query will set a -1 offset rather than 0 for the
+	 * first query of a possibly multi-query string if it wants us to return an
+	 * EOF token.
+	 */
+	yyext->return_eof = (offset != 0);
+
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	if (offset > 0)
+		state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index e941b59b85..9331628add 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -602,17 +602,137 @@ ProcessClientWriteInterrupt(bool blocked)
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list = NIL;
+	List		   *result = NIL;
+	int				stmt_len, offset;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	if (parser_hook)
-		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
-	else
-		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	stmt_len = 0; /* lazily computed when needed */
+	offset = 0;
+
+	while(true)
+	{
+		List *raw_parsetree_list;
+		RawStmt *raw;
+		bool	error = false;
+
+		/*----------------
+		 * Start parsing the input string.  If a third-party module provided a
+		 * parser_hook, we switch to single-query parsing so multi-query
+		 * commands using different grammar can work properly.
+		 * If the third-party modules support the full set of SQL we support,
+		 * or want to prevent fallback on the core parser, it can ignore the
+		 * RAW_PARSE_SINGLE_QUERY flag and parse the full query string.
+		 * In that case they must return a List with more than one RawStmt or a
+		 * single RawStmt with a 0 length to stop the parsing phase, or raise
+		 * an ERROR.
+		 *
+		 * Otherwise, plugins should parse a single query only and always
+		 * return a List containing a single RawStmt with a properly set length
+		 * (possibly 0 if it was a single query without end of query
+		 * delimiter).  If the command is valid but doesn't contain any
+		 * statements (e.g. a single semi-colon), a single RawStmt with a NULL
+		 * stmt field should be returned, containing the consumed query string
+		 * length so we can move to the next command in a single pass rather
+		 * than 1 byte at a time.
+		 *
+		 * Also, third-party modules can choose to ignore some or all of
+		 * parsing error if they want to implement only subset of postgres
+		 * suppoted syntax, or even a totally different syntax, and fall-back
+		 * on core grammar for unhandled case.  In thase case, they should set
+		 * the error flag to true.  The returned List will be ignored and the
+		 * same offset of the input string will be parsed using the core
+		 * parser.
+		 *
+		 * Finally, note that third-party modules that wants to fallback on
+		 * other grammar should first try to call a previous parser hook if any
+		 * before setting the error switch and returning .
+		 */
+		if (parser_hook)
+			raw_parsetree_list = (*parser_hook) (query_string,
+												 RAW_PARSE_SINGLE_QUERY,
+												 offset,
+												 &error);
+
+		/*
+		 * If a third-party module couldn't parse a single query or if no
+		 * third-party module is configured, fallback on core parser.
+		 */
+		if (error || !parser_hook)
+		{
+			/* Send a -1 offset to raw_parser to specify that it should
+			 * explicitly detect EOF during parsing.  scanner_init() will treat
+			 * it the same as a 0 offset.
+			 */
+			raw_parsetree_list = raw_parser(query_string,
+					error ? RAW_PARSE_SINGLE_QUERY : RAW_PARSE_DEFAULT,
+					(error && offset == 0) ? -1 : offset);
+		}
+
+		/*
+		 * If there are no third-party plugin, or none of the parsers found a
+		 * valid query, or if a third party module consumed the whole
+		 * query string we're done.
+		 */
+		if (!parser_hook || raw_parsetree_list == NIL ||
+			list_length(raw_parsetree_list) > 1)
+		{
+			/*
+			 * Warn third-party plugins if they mix "single query" and "whole
+			 * input string" strategy rather than silently accepting it and
+			 * maybe allow fallback on core grammar even if they want to avoid
+			 * that.  This way plugin authors can be warned early of the issue.
+			 */
+			if (result != NIL)
+			{
+				Assert(parser_hook != NULL);
+				elog(ERROR, "parser_hook should parse a single statement at "
+						"a time or consume the whole input string at once");
+			}
+			result = raw_parsetree_list;
+			break;
+		}
+
+		if (stmt_len == 0)
+			stmt_len = strlen(query_string);
+
+		raw = linitial_node(RawStmt, raw_parsetree_list);
+
+		/*
+		 * In single-query mode, the parser will return statement location info
+		 * relative to the beginning of complete original string, not the part
+		 * we just parsed, so adjust the location info.
+		 */
+		if (offset > 0 && raw->stmt_len > 0)
+		{
+			Assert(raw->stmt_len > offset);
+			raw->stmt_location = offset;
+			raw->stmt_len -= offset;
+		}
+
+		/* Ignore the statement if it didn't contain any command. */
+		if (raw->stmt)
+			result = lappend(result, raw);
+
+		if (raw->stmt_len == 0)
+		{
+			/* The statement was the whole string, we're done. */
+			break;
+		}
+		else if (raw->stmt_len + offset >= stmt_len)
+		{
+			/* We consumed all of the input string, we're done. */
+			break;
+		}
+		else
+		{
+			/* Advance the offset to the next command. */
+			offset += raw->stmt_len;
+		}
+	}
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
@@ -620,13 +740,13 @@ pg_parse_query(const char *query_string)
 #ifdef COPY_PARSE_PLAN_TREES
 	/* Optional debugging check: pass raw parsetrees through copyObject() */
 	{
-		List	   *new_list = copyObject(raw_parsetree_list);
+		List	   *new_list = copyObject(result);
 
 		/* This checks both copyObject() and the equal() routines... */
-		if (!equal(new_list, raw_parsetree_list))
+		if (!equal(new_list, result))
 			elog(WARNING, "copyObject() failed to produce an equal raw parse tree");
 		else
-			raw_parsetree_list = new_list;
+			result = new_list;
 	}
 #endif
 
@@ -638,7 +758,7 @@ pg_parse_query(const char *query_string)
 
 	TRACE_POSTGRESQL_QUERY_PARSE_DONE(query_string);
 
-	return raw_parsetree_list;
+	return result;
 }
 
 /*
diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h
index 853b0f1606..5694ae791a 100644
--- a/src/include/parser/parser.h
+++ b/src/include/parser/parser.h
@@ -41,7 +41,8 @@ typedef enum
 	RAW_PARSE_PLPGSQL_EXPR,
 	RAW_PARSE_PLPGSQL_ASSIGN1,
 	RAW_PARSE_PLPGSQL_ASSIGN2,
-	RAW_PARSE_PLPGSQL_ASSIGN3
+	RAW_PARSE_PLPGSQL_ASSIGN3,
+	RAW_PARSE_SINGLE_QUERY
 } RawParseMode;
 
 /* Values for the backslash_quote GUC */
@@ -59,7 +60,7 @@ extern PGDLLIMPORT bool standard_conforming_strings;
 
 
 /* Primary entry point for the raw parsing functions */
-extern List *raw_parser(const char *str, RawParseMode mode);
+extern List *raw_parser(const char *str, RawParseMode mode, int offset);
 
 /* Utility functions exported by gram.y (perhaps these should be elsewhere) */
 extern List *SystemFuncName(char *name);
diff --git a/src/include/parser/scanner.h b/src/include/parser/scanner.h
index 0d8182faa0..a2e97be5d5 100644
--- a/src/include/parser/scanner.h
+++ b/src/include/parser/scanner.h
@@ -113,6 +113,9 @@ typedef struct core_yy_extra_type
 	/* state variables for literal-lexing warnings */
 	bool		warn_on_first_escape;
 	bool		saw_non_ascii;
+
+	/* state variable for returning an EOF token in single query mode */
+	bool		return_eof;
 } core_yy_extra_type;
 
 /*
@@ -136,7 +139,8 @@ extern PGDLLIMPORT const uint16 ScanKeywordTokens[];
 extern core_yyscan_t scanner_init(const char *str,
 								  core_yy_extra_type *yyext,
 								  const ScanKeywordList *keywordlist,
-								  const uint16 *keyword_tokens);
+								  const uint16 *keyword_tokens,
+								  int offset);
 extern void scanner_finish(core_yyscan_t yyscanner);
 extern int	core_yylex(core_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   core_yyscan_t yyscanner);
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 131dc2b22e..27201dde1d 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -45,7 +45,8 @@ typedef enum
 extern PGDLLIMPORT int log_statement;
 
 /* Hook for plugins to get control in pg_parse_query() */
-typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode,
+								   int offset, bool *error);
 extern PGDLLIMPORT parser_hook_type parser_hook;
 
 extern List *pg_parse_query(const char *query_string);
diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y
index 3fcca43b90..e5a8a6477a 100644
--- a/src/pl/plpgsql/src/pl_gram.y
+++ b/src/pl/plpgsql/src/pl_gram.y
@@ -3656,7 +3656,7 @@ check_sql_expr(const char *stmt, RawParseMode parseMode, int location)
 	error_context_stack = &syntax_errcontext;
 
 	oldCxt = MemoryContextSwitchTo(plpgsql_compile_tmp_cxt);
-	(void) raw_parser(stmt, parseMode);
+	(void) raw_parser(stmt, parseMode, 0);
 	MemoryContextSwitchTo(oldCxt);
 
 	/* Restore former ereport callback */
diff --git a/src/pl/plpgsql/src/pl_scanner.c b/src/pl/plpgsql/src/pl_scanner.c
index e4c7a91ab5..a2886c42ec 100644
--- a/src/pl/plpgsql/src/pl_scanner.c
+++ b/src/pl/plpgsql/src/pl_scanner.c
@@ -587,7 +587,7 @@ plpgsql_scanner_init(const char *str)
 {
 	/* Start up the core scanner */
 	yyscanner = scanner_init(str, &core_yy,
-							 &ReservedPLKeywords, ReservedPLKeywordTokens);
+							 &ReservedPLKeywords, ReservedPLKeywordTokens, 0);
 
 	/*
 	 * scanorig points to the original string, which unlike the scanner's
-- 
2.31.1

From 379695587598a0af4490fef22f17f7f28f7df0ad Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 02:15:54 +0800
Subject: [PATCH v3 4/4] Teach sqlol to use the new MODE_SINGLE_QUERY parser
 mode.

This way multi-statements commands using both core parser and sqlol parser can
be supported.

Also add a LOLCODE version of CREATE VIEW viewname AS to easily test
multi-statements commands.
---
 contrib/sqlol/Makefile              |  2 +
 contrib/sqlol/expected/01_sqlol.out | 74 +++++++++++++++++++++++++++++
 contrib/sqlol/repro.sql             | 18 +++++++
 contrib/sqlol/sql/01_sqlol.sql      | 40 ++++++++++++++++
 contrib/sqlol/sqlol.c               | 24 ++++++----
 contrib/sqlol/sqlol_gram.y          | 63 ++++++++++++------------
 contrib/sqlol/sqlol_kwlist.h        |  1 +
 contrib/sqlol/sqlol_scan.l          | 13 ++++-
 contrib/sqlol/sqlol_scanner.h       |  3 +-
 9 files changed, 192 insertions(+), 46 deletions(-)
 create mode 100644 contrib/sqlol/expected/01_sqlol.out
 create mode 100644 contrib/sqlol/repro.sql
 create mode 100644 contrib/sqlol/sql/01_sqlol.sql

diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
index 3850ac3fce..eaf94801c2 100644
--- a/contrib/sqlol/Makefile
+++ b/contrib/sqlol/Makefile
@@ -6,6 +6,8 @@ OBJS = \
 	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
 PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
 
+REGRESS = 01_sqlol
+
 sqlol_gram.h: sqlol_gram.c
 	touch $@
 
diff --git a/contrib/sqlol/expected/01_sqlol.out b/contrib/sqlol/expected/01_sqlol.out
new file mode 100644
index 0000000000..a18eaf6801
--- /dev/null
+++ b/contrib/sqlol/expected/01_sqlol.out
@@ -0,0 +1,74 @@
+LOAD 'sqlol';
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+ id | val 
+----+-----
+(0 rows)
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+ ?column? 
+----------
+        3
+(1 row)
+
+-- test empty statement ignoring
+\;\;select 1 \g
+ ?column? 
+----------
+        1
+(1 row)
+
+-- check the created views
+\d
+       List of relations
+ Schema | Name | Type  | Owner 
+--------+------+-------+-------
+ public | t1   | table | rjuju
+ public | v0   | view  | rjuju
+ public | v1   | view  | rjuju
+ public | v2   | view  | rjuju
+ public | v3   | view  | rjuju
+ public | v4   | view  | rjuju
+ public | v5   | view  | rjuju
+(7 rows)
+
+--
+-- Error position
+--
+SELECT 1\;err;
+ERROR:  syntax error at or near "err"
+LINE 1: SELECT 1;err;
+                 ^
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+ERROR:  syntax error at or near "HAI"
+LINE 1: SELECT 1;HAI 1.2 I HAS A t1 GIMME id KTHXBYE
+                 ^
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+ERROR:  improper qualified name (too many dotted names): some.thing.public.t1
+LINE 1: SELECT 1;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHX...
+                                 ^
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
+ERROR:  relation "notatable" does not exist
+LINE 1: SELECT 1;SELECT * FROM notatable;
+                               ^
diff --git a/contrib/sqlol/repro.sql b/contrib/sqlol/repro.sql
new file mode 100644
index 0000000000..0ebcb53160
--- /dev/null
+++ b/contrib/sqlol/repro.sql
@@ -0,0 +1,18 @@
+DROP TABLE IF EXISTS t1 CASCADE;
+
+LOAD 'sqlol';
+
+\;\; SELECT 1\;
+
+CREATE TABLE t1 (id integer, val text);
+
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+SELECT 1\;SELECT 2\;SELECT 3 \g
+\d
diff --git a/contrib/sqlol/sql/01_sqlol.sql b/contrib/sqlol/sql/01_sqlol.sql
new file mode 100644
index 0000000000..918caf94c0
--- /dev/null
+++ b/contrib/sqlol/sql/01_sqlol.sql
@@ -0,0 +1,40 @@
+LOAD 'sqlol';
+
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+
+-- test empty statement ignoring
+\;\;select 1 \g
+
+-- check the created views
+\d
+
+--
+-- Error position
+--
+SELECT 1\;err;
+
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
index b986966181..7d4e1b631f 100644
--- a/contrib/sqlol/sqlol.c
+++ b/contrib/sqlol/sqlol.c
@@ -26,7 +26,8 @@ static parser_hook_type prev_parser_hook = NULL;
 void		_PG_init(void);
 void		_PG_fini(void);
 
-static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+static List *sqlol_parser_hook(const char *str, RawParseMode mode, int offset,
+							   bool *error);
 
 
 /*
@@ -54,23 +55,25 @@ _PG_fini(void)
  * sqlol_parser_hook: parse our grammar
  */
 static List *
-sqlol_parser_hook(const char *str, RawParseMode mode)
+sqlol_parser_hook(const char *str, RawParseMode mode, int offset, bool *error)
 {
 	sqlol_yyscan_t yyscanner;
 	sqlol_base_yy_extra_type yyextra;
 	int			yyresult;
 
-	if (mode != RAW_PARSE_DEFAULT)
+	if (mode != RAW_PARSE_DEFAULT && mode != RAW_PARSE_SINGLE_QUERY)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	/* initialize the flex scanner */
 	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
-							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords,
+							 offset);
 
 	/* initialize the bison parser */
 	sqlol_parser_init(&yyextra);
@@ -88,9 +91,10 @@ sqlol_parser_hook(const char *str, RawParseMode mode)
 	if (yyresult)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	return yyextra.parsetree;
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
index 64d00d14ca..4c36cfef5e 100644
--- a/contrib/sqlol/sqlol_gram.y
+++ b/contrib/sqlol/sqlol_gram.y
@@ -20,6 +20,7 @@
 
 #include "catalog/namespace.h"
 #include "nodes/makefuncs.h"
+#include "catalog/pg_class_d.h"
 
 #include "sqlol_gramparse.h"
 
@@ -106,10 +107,10 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
 	ResTarget			*target;
 }
 
-%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+%type <node>	stmt toplevel_stmt GimmehStmt MaekStmt simple_gimmeh columnref
 				indirection_el
 
-%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+%type <list>	parse_toplevel rawstmt gimmeh_list indirection
 
 %type <range>	qualified_name
 
@@ -134,22 +135,19 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
  */
 
 /* ordinary key words in alphabetical order */
-%token <keyword> A GIMMEH HAI HAS I KTHXBYE
-
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE MAEK
 
 %%
 
 /*
  *	The target production for the whole parse.
- *
- * Ordinarily we parse a list of statements, but if we see one of the
- * special MODE_XXX symbols as first token, we parse something else.
- * The options here correspond to enum RawParseMode, which see for details.
  */
 parse_toplevel:
-			stmtmulti
+			rawstmt
 			{
 				pg_yyget_extra(yyscanner)->parsetree = $1;
+
+				YYACCEPT;
 			}
 		;
 
@@ -163,24 +161,11 @@ parse_toplevel:
  * we'd get -1 for the location in such cases.
  * We also take care to discard empty statements entirely.
  */
-stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
-				{
-					if ($1 != NIL)
-					{
-						/* update length of previous stmt */
-						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
-					}
-					if ($3 != NULL)
-						$$ = lappend($1, makeRawStmt($3, @2 + 1));
-					else
-						$$ = $1;
-				}
-			| toplevel_stmt
+rawstmt:	toplevel_stmt KTHXBYE
 				{
-					if ($1 != NULL)
-						$$ = list_make1(makeRawStmt($1, 0));
-					else
-						$$ = NIL;
+					RawStmt *raw = makeRawStmt($1, 0);
+					updateRawStmtEnd(raw, @2 + 7);
+					$$ = list_make1(raw);
 				}
 		;
 
@@ -189,13 +174,12 @@ stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
  * those words have different meanings in function bodys.
  */
 toplevel_stmt:
-			stmt
+			HAI FCONST stmt { $$ = $3; }
 		;
 
 stmt:
 			GimmehStmt
-			| /*EMPTY*/
-				{ $$ = NULL; }
+			| MaekStmt
 		;
 
 /*****************************************************************************
@@ -209,12 +193,11 @@ GimmehStmt:
 		;
 
 simple_gimmeh:
-			HAI FCONST I HAS A qualified_name
-			GIMMEH gimmeh_list
+			I HAS A qualified_name GIMMEH gimmeh_list
 				{
 					SelectStmt *n = makeNode(SelectStmt);
-					n->targetList = $8;
-					n->fromClause = list_make1($6);
+					n->targetList = $6;
+					n->fromClause = list_make1($4);
 					$$ = (Node *)n;
 				}
 		;
@@ -233,6 +216,20 @@ gimmeh_el:
 				$$->location = @1;
 			}
 
+MaekStmt:
+		MAEK GimmehStmt A qualified_name
+			{
+				ViewStmt *n = makeNode(ViewStmt);
+				n->view = $4;
+				n->view->relpersistence = RELPERSISTENCE_PERMANENT;
+				n->aliases = NIL;
+				n->query = $2;
+				n->replace = false;
+				n->options = NIL;
+				n->withCheckOption = false;
+				$$ = (Node *) n;
+			}
+
 qualified_name:
 			ColId
 				{
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
index 2de3893ee4..8b50d88df9 100644
--- a/contrib/sqlol/sqlol_kwlist.h
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -19,3 +19,4 @@ PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
 PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
 PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
 PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
+PG_KEYWORD("maek", MAEK, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
index a7088b8390..e6d4d53446 100644
--- a/contrib/sqlol/sqlol_scan.l
+++ b/contrib/sqlol/sqlol_scan.l
@@ -412,8 +412,10 @@ sqlol_yyscan_t
 sqlol_scanner_init(const char *str,
 			 sqlol_yy_extra_type *yyext,
 			 const sqlol_ScanKeyword *keywords,
-			 int num_keywords)
+			 int num_keywords,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -432,13 +434,20 @@ sqlol_scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
index 0a497e9d91..57f95867ee 100644
--- a/contrib/sqlol/sqlol_scanner.h
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -108,7 +108,8 @@ extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
 extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
 								  sqlol_yy_extra_type *yyext,
 								  const sqlol_ScanKeyword *keywords,
-								  int num_keywords);
+								  int num_keywords,
+								  int offset);
 extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
 extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   sqlol_yyscan_t yyscanner);
-- 
2.31.1

From 236c61e4f26b5ef2dedb9ecb7efacb175777fba8 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 22:47:18 +0800
Subject: [PATCH v4 1/4] Add a parser_hook hook.

This does nothing but allow third-party plugins to implement a different
syntax, and fallback on the core parser if they don't implement a superset of
the supported core syntax.
---
 src/backend/tcop/postgres.c | 16 ++++++++++++++--
 src/include/tcop/tcopprot.h |  5 +++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 8cea10c901..e941b59b85 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -99,6 +99,9 @@ int			log_statement = LOGSTMT_NONE;
 /* GUC variable for maximum stack depth (measured in kilobytes) */
 int			max_stack_depth = 100;
 
+/* Hook for plugins to get control in pg_parse_query() */
+parser_hook_type parser_hook = NULL;
+
 /* wait N seconds to allow attach from a debugger */
 int			PostAuthDelay = 0;
 
@@ -589,18 +592,27 @@ ProcessClientWriteInterrupt(bool blocked)
  * database tables.  So, we rely on the raw parser to determine whether
  * we've seen a COMMIT or ABORT command; when we are in abort state, other
  * commands are not processed any further than the raw parse stage.
+ *
+ * To support loadable plugins that monitor the parsing or implements SQL
+ * syntactic sugar we provide a hook variable that lets a plugin get control
+ * before and after the standard parsing process.  If the plugin only implement
+ * a subset of postgres supported syntax, it's its duty to call raw_parser (or
+ * the previous hook if any) for the statements it doesn't understand.
  */
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list;
+	List	   *raw_parsetree_list = NIL;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	if (parser_hook)
+		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
+	else
+		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 968345404e..131dc2b22e 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -17,6 +17,7 @@
 #include "nodes/params.h"
 #include "nodes/parsenodes.h"
 #include "nodes/plannodes.h"
+#include "parser/parser.h"
 #include "storage/procsignal.h"
 #include "utils/guc.h"
 #include "utils/queryenvironment.h"
@@ -43,6 +44,10 @@ typedef enum
 
 extern PGDLLIMPORT int log_statement;
 
+/* Hook for plugins to get control in pg_parse_query() */
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+extern PGDLLIMPORT parser_hook_type parser_hook;
+
 extern List *pg_parse_query(const char *query_string);
 extern List *pg_rewrite_query(Query *query);
 extern List *pg_analyze_and_rewrite(RawStmt *parsetree,
-- 
2.31.1

From dcd5a2b45fcc65724ac81e78afb0611e310f15e7 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 23:54:02 +0800
Subject: [PATCH v4 2/4] Add a sqlol parser.

This is a toy example of alternative grammar that only accept a LOLCODE
compatible version of a

SELECT [column, ] column FROM tablename

and fallback on the core parser for everything else.
---
 contrib/Makefile                |   1 +
 contrib/sqlol/.gitignore        |   7 +
 contrib/sqlol/Makefile          |  33 ++
 contrib/sqlol/sqlol.c           | 107 +++++++
 contrib/sqlol/sqlol_gram.y      | 440 ++++++++++++++++++++++++++
 contrib/sqlol/sqlol_gramparse.h |  61 ++++
 contrib/sqlol/sqlol_keywords.c  |  98 ++++++
 contrib/sqlol/sqlol_keywords.h  |  38 +++
 contrib/sqlol/sqlol_kwlist.h    |  21 ++
 contrib/sqlol/sqlol_scan.l      | 544 ++++++++++++++++++++++++++++++++
 contrib/sqlol/sqlol_scanner.h   | 118 +++++++
 11 files changed, 1468 insertions(+)
 create mode 100644 contrib/sqlol/.gitignore
 create mode 100644 contrib/sqlol/Makefile
 create mode 100644 contrib/sqlol/sqlol.c
 create mode 100644 contrib/sqlol/sqlol_gram.y
 create mode 100644 contrib/sqlol/sqlol_gramparse.h
 create mode 100644 contrib/sqlol/sqlol_keywords.c
 create mode 100644 contrib/sqlol/sqlol_keywords.h
 create mode 100644 contrib/sqlol/sqlol_kwlist.h
 create mode 100644 contrib/sqlol/sqlol_scan.l
 create mode 100644 contrib/sqlol/sqlol_scanner.h

diff --git a/contrib/Makefile b/contrib/Makefile
index f27e458482..2a80cd137b 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -43,6 +43,7 @@ SUBDIRS = \
 		postgres_fdw	\
 		seg		\
 		spi		\
+		sqlol		\
 		tablefunc	\
 		tcn		\
 		test_decoding	\
diff --git a/contrib/sqlol/.gitignore b/contrib/sqlol/.gitignore
new file mode 100644
index 0000000000..3c4b587792
--- /dev/null
+++ b/contrib/sqlol/.gitignore
@@ -0,0 +1,7 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
+sqlol_gram.c
+sqlol_gram.h
+sqlol_scan.c
diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
new file mode 100644
index 0000000000..3850ac3fce
--- /dev/null
+++ b/contrib/sqlol/Makefile
@@ -0,0 +1,33 @@
+# contrib/sqlol/Makefile
+
+MODULE_big = sqlol
+OBJS = \
+	$(WIN32RES) \
+	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
+PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
+
+sqlol_gram.h: sqlol_gram.c
+	touch $@
+
+sqlol_gram.c: BISONFLAGS += -d
+# sqlol_gram.c: BISON_CHECK_CMD = $(PERL) $(srcdir)/check_keywords.pl $< $(top_srcdir)/src/include/parser/kwlist.h
+
+
+sqlol_scan.c: FLEXFLAGS = -CF -p -p
+sqlol_scan.c: FLEX_NO_BACKUP=yes
+sqlol_scan.c: FLEX_FIX_WARNING=yes
+
+
+# Force these dependencies to be known even without dependency info built:
+sqlol.o sqlol_gram.o sqlol_scan.o parser.o: sqlol_gram.h
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/sqlol
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
new file mode 100644
index 0000000000..b986966181
--- /dev/null
+++ b/contrib/sqlol/sqlol.c
@@ -0,0 +1,107 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol.c
+ *
+ *
+ * Copyright (c) 2008-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "tcop/tcopprot.h"
+
+#include "sqlol_gramparse.h"
+#include "sqlol_keywords.h"
+
+PG_MODULE_MAGIC;
+
+
+/* Saved hook values in case of unload */
+static parser_hook_type prev_parser_hook = NULL;
+
+void		_PG_init(void);
+void		_PG_fini(void);
+
+static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+
+
+/*
+ * Module load callback
+ */
+void
+_PG_init(void)
+{
+	/* Install hooks. */
+	prev_parser_hook = parser_hook;
+	parser_hook = sqlol_parser_hook;
+}
+
+/*
+ * Module unload callback
+ */
+void
+_PG_fini(void)
+{
+	/* Uninstall hooks. */
+	parser_hook = prev_parser_hook;
+}
+
+/*
+ * sqlol_parser_hook: parse our grammar
+ */
+static List *
+sqlol_parser_hook(const char *str, RawParseMode mode)
+{
+	sqlol_yyscan_t yyscanner;
+	sqlol_base_yy_extra_type yyextra;
+	int			yyresult;
+
+	if (mode != RAW_PARSE_DEFAULT)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	/* initialize the flex scanner */
+	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+
+	/* initialize the bison parser */
+	sqlol_parser_init(&yyextra);
+
+	/* Parse! */
+	yyresult = sqlol_base_yyparse(yyscanner);
+
+	/* Clean up (release memory) */
+	sqlol_scanner_finish(yyscanner);
+
+	/*
+	 * Invalid statement, fallback on previous parser_hook if any or
+	 * raw_parser()
+	 */
+	if (yyresult)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	return yyextra.parsetree;
+}
+
+int
+sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, sqlol_yyscan_t yyscanner)
+{
+	int			cur_token;
+
+	cur_token = sqlol_yylex(&(lvalp->sqlol_yystype), llocp, yyscanner);
+
+	return cur_token;
+}
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
new file mode 100644
index 0000000000..64d00d14ca
--- /dev/null
+++ b/contrib/sqlol/sqlol_gram.y
@@ -0,0 +1,440 @@
+%{
+
+/*#define YYDEBUG 1*/
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gram.y
+ *	  sqlol BISON rules/actions
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_gram.y
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "catalog/namespace.h"
+#include "nodes/makefuncs.h"
+
+#include "sqlol_gramparse.h"
+
+/*
+ * Location tracking support --- simpler than bison's default, since we only
+ * want to track the start position not the end position of each nonterminal.
+ */
+#define YYLLOC_DEFAULT(Current, Rhs, N) \
+	do { \
+		if ((N) > 0) \
+			(Current) = (Rhs)[1]; \
+		else \
+			(Current) = (-1); \
+	} while (0)
+
+/*
+ * The above macro assigns -1 (unknown) as the parse location of any
+ * nonterminal that was reduced from an empty rule, or whose leftmost
+ * component was reduced from an empty rule.  This is problematic
+ * for nonterminals defined like
+ *		OptFooList: / * EMPTY * / { ... } | OptFooList Foo { ... } ;
+ * because we'll set -1 as the location during the first reduction and then
+ * copy it during each subsequent reduction, leaving us with -1 for the
+ * location even when the list is not empty.  To fix that, do this in the
+ * action for the nonempty rule(s):
+ *		if (@$ < 0) @$ = @2;
+ * (Although we have many nonterminals that follow this pattern, we only
+ * bother with fixing @$ like this when the nonterminal's parse location
+ * is actually referenced in some rule.)
+ *
+ * A cleaner answer would be to make YYLLOC_DEFAULT scan all the Rhs
+ * locations until it's found one that's not -1.  Then we'd get a correct
+ * location for any nonterminal that isn't entirely empty.  But this way
+ * would add overhead to every rule reduction, and so far there's not been
+ * a compelling reason to pay that overhead.
+ */
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+
+#define parser_yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+#define parser_errposition(pos)  sqlol_scanner_errposition(pos, yyscanner)
+
+static void sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner,
+						 const char *msg);
+static RawStmt *makeRawStmt(Node *stmt, int stmt_location);
+static void updateRawStmtEnd(RawStmt *rs, int end_location);
+static Node *makeColumnRef(char *colname, List *indirection,
+						   int location, sqlol_yyscan_t yyscanner);
+static void check_qualified_name(List *names, sqlol_yyscan_t yyscanner);
+static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
+
+%}
+
+%pure-parser
+%expect 0
+%name-prefix="sqlol_base_yy"
+%locations
+
+%parse-param {sqlol_yyscan_t yyscanner}
+%lex-param   {sqlol_yyscan_t yyscanner}
+
+%union
+{
+	sqlol_YYSTYPE		sqlol_yystype;
+	/* these fields must match sqlol_YYSTYPE: */
+	int					ival;
+	char				*str;
+	const char			*keyword;
+
+	List				*list;
+	Node				*node;
+	Value				*value;
+	RangeVar			*range;
+	ResTarget			*target;
+}
+
+%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+				indirection_el
+
+%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+
+%type <range>	qualified_name
+
+%type <str>		ColId ColLabel attr_name
+
+%type <target>	gimmeh_el
+
+/*
+ * Non-keyword token types.  These are hard-wired into the "flex" lexer.
+ * They must be listed first so that their numeric codes do not depend on
+ * the set of keywords.  PL/pgSQL depends on this so that it can share the
+ * same lexer.  If you add/change tokens here, fix PL/pgSQL to match!
+ *
+ */
+%token <str>	IDENT FCONST SCONST Op
+
+/*
+ * If you want to make any keyword changes, update the keyword table in
+ * src/include/parser/kwlist.h and add new keywords to the appropriate one
+ * of the reserved-or-not-so-reserved keyword lists, below; search
+ * this file for "Keyword category lists".
+ */
+
+/* ordinary key words in alphabetical order */
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE
+
+
+%%
+
+/*
+ *	The target production for the whole parse.
+ *
+ * Ordinarily we parse a list of statements, but if we see one of the
+ * special MODE_XXX symbols as first token, we parse something else.
+ * The options here correspond to enum RawParseMode, which see for details.
+ */
+parse_toplevel:
+			stmtmulti
+			{
+				pg_yyget_extra(yyscanner)->parsetree = $1;
+			}
+		;
+
+/*
+ * At top level, we wrap each stmt with a RawStmt node carrying start location
+ * and length of the stmt's text.  Notice that the start loc/len are driven
+ * entirely from semicolon locations (@2).  It would seem natural to use
+ * @1 or @3 to get the true start location of a stmt, but that doesn't work
+ * for statements that can start with empty nonterminals (opt_with_clause is
+ * the main offender here); as noted in the comments for YYLLOC_DEFAULT,
+ * we'd get -1 for the location in such cases.
+ * We also take care to discard empty statements entirely.
+ */
+stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
+				{
+					if ($1 != NIL)
+					{
+						/* update length of previous stmt */
+						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
+					}
+					if ($3 != NULL)
+						$$ = lappend($1, makeRawStmt($3, @2 + 1));
+					else
+						$$ = $1;
+				}
+			| toplevel_stmt
+				{
+					if ($1 != NULL)
+						$$ = list_make1(makeRawStmt($1, 0));
+					else
+						$$ = NIL;
+				}
+		;
+
+/*
+ * toplevel_stmt includes BEGIN and END.  stmt does not include them, because
+ * those words have different meanings in function bodys.
+ */
+toplevel_stmt:
+			stmt
+		;
+
+stmt:
+			GimmehStmt
+			| /*EMPTY*/
+				{ $$ = NULL; }
+		;
+
+/*****************************************************************************
+ *
+ * GIMMEH statement
+ *
+ *****************************************************************************/
+
+GimmehStmt:
+			simple_gimmeh						{ $$ = $1; }
+		;
+
+simple_gimmeh:
+			HAI FCONST I HAS A qualified_name
+			GIMMEH gimmeh_list
+				{
+					SelectStmt *n = makeNode(SelectStmt);
+					n->targetList = $8;
+					n->fromClause = list_make1($6);
+					$$ = (Node *)n;
+				}
+		;
+
+gimmeh_list:
+		   gimmeh_el							{ $$ = list_make1($1); }
+		   | gimmeh_list ',' gimmeh_el			{ $$ = lappend($1, $3); }
+
+gimmeh_el:
+		 columnref
+			{
+				$$ = makeNode(ResTarget);
+				$$->name = NULL;
+				$$->indirection = NIL;
+				$$->val = (Node *)$1;
+				$$->location = @1;
+			}
+
+qualified_name:
+			ColId
+				{
+					$$ = makeRangeVar(NULL, $1, @1);
+				}
+			| ColId indirection
+				{
+					check_qualified_name($2, yyscanner);
+					$$ = makeRangeVar(NULL, NULL, @1);
+					switch (list_length($2))
+					{
+						case 1:
+							$$->catalogname = NULL;
+							$$->schemaname = $1;
+							$$->relname = strVal(linitial($2));
+							break;
+						case 2:
+							$$->catalogname = $1;
+							$$->schemaname = strVal(linitial($2));
+							$$->relname = strVal(lsecond($2));
+							break;
+						default:
+							/*
+							 * It's ok to error out here as at this point we
+							 * already parsed a "HAI FCONST" preamble, and no
+							 * other grammar is likely to accept a command
+							 * starting with that, so there's no point trying
+							 * to fall back on the other grammars.
+							 */
+							ereport(ERROR,
+									(errcode(ERRCODE_SYNTAX_ERROR),
+									 errmsg("improper qualified name (too many dotted names): %s",
+											NameListToString(lcons(makeString($1), $2))),
+									 parser_errposition(@1)));
+							break;
+					}
+				}
+		;
+
+columnref:	ColId
+				{
+					$$ = makeColumnRef($1, NIL, @1, yyscanner);
+				}
+			| ColId indirection
+				{
+					$$ = makeColumnRef($1, $2, @1, yyscanner);
+				}
+		;
+
+ColId:		IDENT									{ $$ = $1; }
+
+indirection:
+			indirection_el							{ $$ = list_make1($1); }
+			| indirection indirection_el			{ $$ = lappend($1, $2); }
+		;
+
+indirection_el:
+			'.' attr_name
+				{
+					$$ = (Node *) makeString($2);
+				}
+		;
+
+attr_name:	ColLabel								{ $$ = $1; };
+
+ColLabel:	IDENT									{ $$ = $1; }
+
+%%
+
+/*
+ * The signature of this function is required by bison.  However, we
+ * ignore the passed yylloc and instead use the last token position
+ * available from the scanner.
+ */
+static void
+sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner, const char *msg)
+{
+	parser_yyerror(msg);
+}
+
+static RawStmt *
+makeRawStmt(Node *stmt, int stmt_location)
+{
+	RawStmt    *rs = makeNode(RawStmt);
+
+	rs->stmt = stmt;
+	rs->stmt_location = stmt_location;
+	rs->stmt_len = 0;			/* might get changed later */
+	return rs;
+}
+
+/* Adjust a RawStmt to reflect that it doesn't run to the end of the string */
+static void
+updateRawStmtEnd(RawStmt *rs, int end_location)
+{
+	/*
+	 * If we already set the length, don't change it.  This is for situations
+	 * like "select foo ;; select bar" where the same statement will be last
+	 * in the string for more than one semicolon.
+	 */
+	if (rs->stmt_len > 0)
+		return;
+
+	/* OK, update length of RawStmt */
+	rs->stmt_len = end_location - rs->stmt_location;
+}
+
+static Node *
+makeColumnRef(char *colname, List *indirection,
+			  int location, sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * Generate a ColumnRef node, with an A_Indirection node added if there
+	 * is any subscripting in the specified indirection list.  However,
+	 * any field selection at the start of the indirection list must be
+	 * transposed into the "fields" part of the ColumnRef node.
+	 */
+	ColumnRef  *c = makeNode(ColumnRef);
+	int		nfields = 0;
+	ListCell *l;
+
+	c->location = location;
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Indices))
+		{
+			A_Indirection *i = makeNode(A_Indirection);
+
+			if (nfields == 0)
+			{
+				/* easy case - all indirection goes to A_Indirection */
+				c->fields = list_make1(makeString(colname));
+				i->indirection = check_indirection(indirection, yyscanner);
+			}
+			else
+			{
+				/* got to split the list in two */
+				i->indirection = check_indirection(list_copy_tail(indirection,
+																  nfields),
+												   yyscanner);
+				indirection = list_truncate(indirection, nfields);
+				c->fields = lcons(makeString(colname), indirection);
+			}
+			i->arg = (Node *) c;
+			return (Node *) i;
+		}
+		else if (IsA(lfirst(l), A_Star))
+		{
+			/* We only allow '*' at the end of a ColumnRef */
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+		nfields++;
+	}
+	/* No subscripting, so all indirection gets added to field list */
+	c->fields = lcons(makeString(colname), indirection);
+	return (Node *) c;
+}
+
+/* check_qualified_name --- check the result of qualified_name production
+ *
+ * It's easiest to let the grammar production for qualified_name allow
+ * subscripts and '*', which we then must reject here.
+ */
+static void
+check_qualified_name(List *names, sqlol_yyscan_t yyscanner)
+{
+	ListCell   *i;
+
+	foreach(i, names)
+	{
+		if (!IsA(lfirst(i), String))
+			parser_yyerror("syntax error");
+	}
+}
+
+/* check_indirection --- check the result of indirection production
+ *
+ * We only allow '*' at the end of the list, but it's hard to enforce that
+ * in the grammar, so do it here.
+ */
+static List *
+check_indirection(List *indirection, sqlol_yyscan_t yyscanner)
+{
+	ListCell *l;
+
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Star))
+		{
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+	}
+	return indirection;
+}
+
+/* sqlol_parser_init()
+ * Initialize to parse one query string
+ */
+void
+sqlol_parser_init(sqlol_base_yy_extra_type *yyext)
+{
+	yyext->parsetree = NIL;		/* in case grammar forgets to set it */
+}
diff --git a/contrib/sqlol/sqlol_gramparse.h b/contrib/sqlol/sqlol_gramparse.h
new file mode 100644
index 0000000000..58233a8d87
--- /dev/null
+++ b/contrib/sqlol/sqlol_gramparse.h
@@ -0,0 +1,61 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gramparse.h
+ *		Shared definitions for the "raw" parser (flex and bison phases only)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_gramparse.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_GRAMPARSE_H
+#define SQLOL_GRAMPARSE_H
+
+#include "nodes/parsenodes.h"
+#include "sqlol_scanner.h"
+
+/*
+ * NB: include gram.h only AFTER including scanner.h, because scanner.h
+ * is what #defines YYLTYPE.
+ */
+#include "sqlol_gram.h"
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.  Private
+ * state needed for raw parsing/lexing goes here.
+ */
+typedef struct sqlol_base_yy_extra_type
+{
+	/*
+	 * Fields used by the core scanner.
+	 */
+	sqlol_yy_extra_type sqlol_yy_extra;
+
+	/*
+	 * State variables that belong to the grammar.
+	 */
+	List	   *parsetree;		/* final parse result is delivered here */
+} sqlol_base_yy_extra_type;
+
+/*
+ * In principle we should use yyget_extra() to fetch the yyextra field
+ * from a yyscanner struct.  However, flex always puts that field first,
+ * and this is sufficiently performance-critical to make it seem worth
+ * cheating a bit to use an inline macro.
+ */
+#define pg_yyget_extra(yyscanner) (*((sqlol_base_yy_extra_type **) (yyscanner)))
+
+
+/* from parser.c */
+extern int	sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+
+/* from gram.y */
+extern void sqlol_parser_init(sqlol_base_yy_extra_type *yyext);
+extern int	sqlol_baseyyparse(sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_GRAMPARSE_H */
diff --git a/contrib/sqlol/sqlol_keywords.c b/contrib/sqlol/sqlol_keywords.c
new file mode 100644
index 0000000000..dbbdf5493c
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.c
@@ -0,0 +1,98 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.c
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  sqlol/sqlol_keywords.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "sqlol_gramparse.h"
+
+#define PG_KEYWORD(a,b,c) {a,b,c},
+
+const sqlol_ScanKeyword sqlol_ScanKeywords[] = {
+#include "sqlol_kwlist.h"
+};
+
+const int	sqlol_NumScanKeywords = lengthof(sqlol_ScanKeywords);
+
+#undef PG_KEYWORD
+
+
+/*
+ * ScanKeywordLookup - see if a given word is a keyword
+ *
+ * The table to be searched is passed explicitly, so that this can be used
+ * to search keyword lists other than the standard list appearing above.
+ *
+ * Returns a pointer to the sqlol_ScanKeyword table entry, or NULL if no match.
+ *
+ * The match is done case-insensitively.  Note that we deliberately use a
+ * dumbed-down case conversion that will only translate 'A'-'Z' into 'a'-'z',
+ * even if we are in a locale where tolower() would produce more or different
+ * translations.  This is to conform to the SQL99 spec, which says that
+ * keywords are to be matched in this way even though non-keyword identifiers
+ * receive a different case-normalization mapping.
+ */
+const sqlol_ScanKeyword *
+sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords)
+{
+	int			len,
+				i;
+	char		word[NAMEDATALEN];
+	const sqlol_ScanKeyword *low;
+	const sqlol_ScanKeyword *high;
+
+	len = strlen(text);
+	/* We assume all keywords are shorter than NAMEDATALEN. */
+	if (len >= NAMEDATALEN)
+		return NULL;
+
+	/*
+	 * Apply an ASCII-only downcasing.  We must not use tolower() since it may
+	 * produce the wrong translation in some locales (eg, Turkish).
+	 */
+	for (i = 0; i < len; i++)
+	{
+		char		ch = text[i];
+
+		if (ch >= 'A' && ch <= 'Z')
+			ch += 'a' - 'A';
+		word[i] = ch;
+	}
+	word[len] = '\0';
+
+	/*
+	 * Now do a binary search using plain strcmp() comparison.
+	 */
+	low = keywords;
+	high = keywords + (num_keywords - 1);
+	while (low <= high)
+	{
+		const sqlol_ScanKeyword *middle;
+		int			difference;
+
+		middle = low + (high - low) / 2;
+		difference = strcmp(middle->name, word);
+		if (difference == 0)
+			return middle;
+		else if (difference < 0)
+			low = middle + 1;
+		else
+			high = middle - 1;
+	}
+
+	return NULL;
+}
+
diff --git a/contrib/sqlol/sqlol_keywords.h b/contrib/sqlol/sqlol_keywords.h
new file mode 100644
index 0000000000..bc4acf4541
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.h
@@ -0,0 +1,38 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.h
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_keywords.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SQLOL_KEYWORDS_H
+#define SQLOL_KEYWORDS_H
+
+/* Keyword categories --- should match lists in gram.y */
+#define UNRESERVED_KEYWORD		0
+#define COL_NAME_KEYWORD		1
+#define TYPE_FUNC_NAME_KEYWORD	2
+#define RESERVED_KEYWORD		3
+
+
+typedef struct sqlol_ScanKeyword
+{
+	const char *name;			/* in lower case */
+	int16		value;			/* grammar's token code */
+	int16		category;		/* see codes above */
+} sqlol_ScanKeyword;
+
+extern PGDLLIMPORT const sqlol_ScanKeyword sqlol_ScanKeywords[];
+extern PGDLLIMPORT const int sqlol_NumScanKeywords;
+
+extern const sqlol_ScanKeyword *sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords);
+
+#endif							/* SQLOL_KEYWORDS_H */
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
new file mode 100644
index 0000000000..2de3893ee4
--- /dev/null
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -0,0 +1,21 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_kwlist.h
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_kwlist.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* name, value, category, is-bare-label */
+PG_KEYWORD("a", A, UNRESERVED_KEYWORD)
+PG_KEYWORD("gimmeh", GIMMEH, UNRESERVED_KEYWORD)
+PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
+PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
+PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
+PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
new file mode 100644
index 0000000000..a7088b8390
--- /dev/null
+++ b/contrib/sqlol/sqlol_scan.l
@@ -0,0 +1,544 @@
+%top{
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scan.l
+ *	  lexical scanner for sqlol
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_scan.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "common/string.h"
+#include "sqlol_gramparse.h"
+#include "parser/scansup.h"
+#include "mb/pg_wchar.h"
+
+#include "sqlol_keywords.h"
+}
+
+%{
+
+/* LCOV_EXCL_START */
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+
+/*
+ * Set the type of YYSTYPE.
+ */
+#define YYSTYPE sqlol_YYSTYPE
+
+/*
+ * Set the type of yyextra.  All state variables used by the scanner should
+ * be in yyextra, *not* statically allocated.
+ */
+#define YY_EXTRA_TYPE sqlol_yy_extra_type *
+
+/*
+ * Each call to yylex must set yylloc to the location of the found token
+ * (expressed as a byte offset from the start of the input text).
+ * When we parse a token that requires multiple lexer rules to process,
+ * this should be done in the first such rule, else yylloc will point
+ * into the middle of the token.
+ */
+#define SET_YYLLOC()  (*(yylloc) = yytext - yyextra->scanbuf)
+
+/*
+ * Advance yylloc by the given number of bytes.
+ */
+#define ADVANCE_YYLLOC(delta)  ( *(yylloc) += (delta) )
+
+/*
+ * Sometimes, we do want yylloc to point into the middle of a token; this is
+ * useful for instance to throw an error about an escape sequence within a
+ * string literal.  But if we find no error there, we want to revert yylloc
+ * to the token start, so that that's the location reported to the parser.
+ * Use PUSH_YYLLOC/POP_YYLLOC to save/restore yylloc around such code.
+ * (Currently the implied "stack" is just one location, but someday we might
+ * need to nest these.)
+ */
+#define PUSH_YYLLOC()	(yyextra->save_yylloc = *(yylloc))
+#define POP_YYLLOC()	(*(yylloc) = yyextra->save_yylloc)
+
+#define startlit()	( yyextra->literallen = 0 )
+static void addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner);
+static void addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner);
+static char *litbufdup(sqlol_yyscan_t yyscanner);
+
+#define yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+
+#define lexer_errposition()  sqlol_scanner_errposition(*(yylloc), yyscanner)
+
+/*
+ * Work around a bug in flex 2.5.35: it emits a couple of functions that
+ * it forgets to emit declarations for.  Since we use -Wmissing-prototypes,
+ * this would cause warnings.  Providing our own declarations should be
+ * harmless even when the bug gets fixed.
+ */
+extern int	sqlol_yyget_column(yyscan_t yyscanner);
+extern void sqlol_yyset_column(int column_no, yyscan_t yyscanner);
+
+%}
+
+%option reentrant
+%option bison-bridge
+%option bison-locations
+%option 8bit
+%option never-interactive
+%option nodefault
+%option noinput
+%option nounput
+%option noyywrap
+%option noyyalloc
+%option noyyrealloc
+%option noyyfree
+%option warn
+%option prefix="sqlol_yy"
+
+/*
+ * OK, here is a short description of lex/flex rules behavior.
+ * The longest pattern which matches an input string is always chosen.
+ * For equal-length patterns, the first occurring in the rules list is chosen.
+ * INITIAL is the starting state, to which all non-conditional rules apply.
+ * Exclusive states change parsing rules while the state is active.  When in
+ * an exclusive state, only those rules defined for that state apply.
+ *
+ * We use exclusive states for quoted strings, extended comments,
+ * and to eliminate parsing troubles for numeric strings.
+ * Exclusive states:
+ *  <xd> delimited identifiers (double-quoted identifiers)
+ *  <xq> standard quoted strings
+ *  <xqs> quote stop (detect continued strings)
+ *
+ * Remember to add an <<EOF>> case whenever you add a new exclusive state!
+ * The default one is probably not the right thing.
+ */
+
+%x xd
+%x xq
+%x xqs
+
+/*
+ * In order to make the world safe for Windows and Mac clients as well as
+ * Unix ones, we accept either \n or \r as a newline.  A DOS-style \r\n
+ * sequence will be seen as two successive newlines, but that doesn't cause
+ * any problems.  Comments that start with -- and extend to the next
+ * newline are treated as equivalent to a single whitespace character.
+ *
+ * NOTE a fine point: if there is no newline following --, we will absorb
+ * everything to the end of the input as a comment.  This is correct.  Older
+ * versions of Postgres failed to recognize -- as a comment if the input
+ * did not end with a newline.
+ *
+ * XXX perhaps \f (formfeed) should be treated as a newline as well?
+ *
+ * XXX if you change the set of whitespace characters, fix scanner_isspace()
+ * to agree.
+ */
+
+space			[ \t\n\r\f]
+horiz_space		[ \t\f]
+newline			[\n\r]
+non_newline		[^\n\r]
+
+comment			("--"{non_newline}*)
+
+whitespace		({space}+|{comment})
+
+/*
+ * SQL requires at least one newline in the whitespace separating
+ * string literals that are to be concatenated.  Silly, but who are we
+ * to argue?  Note that {whitespace_with_newline} should not have * after
+ * it, whereas {whitespace} should generally have a * after it...
+ */
+
+special_whitespace		({space}+|{comment}{newline})
+horiz_whitespace		({horiz_space}|{comment})
+whitespace_with_newline	({horiz_whitespace}*{newline}{special_whitespace}*)
+
+quote			'
+/* If we see {quote} then {quotecontinue}, the quoted string continues */
+quotecontinue	{whitespace_with_newline}{quote}
+
+/*
+ * {quotecontinuefail} is needed to avoid lexer backup when we fail to match
+ * {quotecontinue}.  It might seem that this could just be {whitespace}*,
+ * but if there's a dash after {whitespace_with_newline}, it must be consumed
+ * to see if there's another dash --- which would start a {comment} and thus
+ * allow continuation of the {quotecontinue} token.
+ */
+quotecontinuefail	{whitespace}*"-"?
+
+/* Extended quote
+ * xqdouble implements embedded quote, ''''
+ */
+xqstart			{quote}
+xqdouble		{quote}{quote}
+xqinside		[^']+
+
+/* Double quote
+ * Allows embedded spaces and other special characters into identifiers.
+ */
+dquote			\"
+xdstart			{dquote}
+xdstop			{dquote}
+xddouble		{dquote}{dquote}
+xdinside		[^"]+
+
+digit			[0-9]
+ident_start		[A-Za-z\200-\377_]
+ident_cont		[A-Za-z\200-\377_0-9\$]
+
+identifier		{ident_start}{ident_cont}*
+
+decimal			(({digit}+)|({digit}*\.{digit}+)|({digit}+\.{digit}*))
+
+other			.
+
+%%
+
+{whitespace}	{
+					/* ignore */
+				}
+
+
+{xqstart}		{
+					yyextra->saw_non_ascii = false;
+					SET_YYLLOC();
+					BEGIN(xq);
+					startlit();
+}
+<xq>{quote} {
+					/*
+					 * When we are scanning a quoted string and see an end
+					 * quote, we must look ahead for a possible continuation.
+					 * If we don't see one, we know the end quote was in fact
+					 * the end of the string.  To reduce the lexer table size,
+					 * we use a single "xqs" state to do the lookahead for all
+					 * types of strings.
+					 */
+					yyextra->state_before_str_stop = YYSTATE;
+					BEGIN(xqs);
+				}
+<xqs>{quotecontinue} {
+					/*
+					 * Found a quote continuation, so return to the in-quote
+					 * state and continue scanning the literal.  Nothing is
+					 * added to the literal's contents.
+					 */
+					BEGIN(yyextra->state_before_str_stop);
+				}
+<xqs>{quotecontinuefail} |
+<xqs>{other} |
+<xqs><<EOF>>	{
+					/*
+					 * Failed to see a quote continuation.  Throw back
+					 * everything after the end quote, and handle the string
+					 * according to the state we were in previously.
+					 */
+					yyless(0);
+					BEGIN(INITIAL);
+
+					switch (yyextra->state_before_str_stop)
+					{
+						case xq:
+							/*
+							 * Check that the data remains valid, if it might
+							 * have been made invalid by unescaping any chars.
+							 */
+							if (yyextra->saw_non_ascii)
+								pg_verifymbstr(yyextra->literalbuf,
+										yyextra->literallen,
+										false);
+							yylval->str = litbufdup(yyscanner);
+							return SCONST;
+						default:
+							yyerror("unhandled previous state in xqs");
+					}
+				}
+
+<xq>{xqdouble} {
+					addlitchar('\'', yyscanner);
+				}
+<xq>{xqinside}  {
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xq><<EOF>>		{ yyerror("unterminated quoted string"); }
+
+
+{xdstart}		{
+					SET_YYLLOC();
+					BEGIN(xd);
+					startlit();
+				}
+<xd>{xdstop}	{
+					char	   *ident;
+
+					BEGIN(INITIAL);
+					if (yyextra->literallen == 0)
+						yyerror("zero-length delimited identifier");
+					ident = litbufdup(yyscanner);
+					if (yyextra->literallen >= NAMEDATALEN)
+						truncate_identifier(ident, yyextra->literallen, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+<xd>{xddouble}	{
+					addlitchar('"', yyscanner);
+				}
+<xd>{xdinside}	{
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xd><<EOF>>		{ yyerror("unterminated quoted identifier"); }
+
+{decimal}		{
+					SET_YYLLOC();
+					yylval->str = pstrdup(yytext);
+					return FCONST;
+				}
+
+{identifier}	{
+					const sqlol_ScanKeyword *keyword;
+					char	   *ident;
+
+					SET_YYLLOC();
+
+					/* Is it a keyword? */
+					keyword = sqlol_ScanKeywordLookup(yytext,
+													yyextra->keywords,
+													yyextra->num_keywords);
+					if (keyword != NULL)
+					{
+						yylval->keyword = keyword->name;
+						return keyword->value;
+					}
+
+					/*
+					 * No.  Convert the identifier to lower case, and truncate
+					 * if necessary.
+					 */
+					ident = downcase_truncate_identifier(yytext, yyleng, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+
+{other}			{
+					SET_YYLLOC();
+					return yytext[0];
+				}
+
+<<EOF>>			{
+					SET_YYLLOC();
+					yyterminate();
+				}
+
+%%
+
+/* LCOV_EXCL_STOP */
+
+/*
+ * Arrange access to yyextra for subroutines of the main yylex() function.
+ * We expect each subroutine to have a yyscanner parameter.  Rather than
+ * use the yyget_xxx functions, which might or might not get inlined by the
+ * compiler, we cheat just a bit and cast yyscanner to the right type.
+ */
+#undef yyextra
+#define yyextra  (((struct yyguts_t *) yyscanner)->yyextra_r)
+
+/* Likewise for a couple of other things we need. */
+#undef yylloc
+#define yylloc	(((struct yyguts_t *) yyscanner)->yylloc_r)
+#undef yyleng
+#define yyleng	(((struct yyguts_t *) yyscanner)->yyleng_r)
+
+
+/*
+ * scanner_errposition
+ *		Report a lexer or grammar error cursor position, if possible.
+ *
+ * This is expected to be used within an ereport() call.  The return value
+ * is a dummy (always 0, in fact).
+ *
+ * Note that this can only be used for messages emitted during raw parsing
+ * (essentially, sqlol_scan.l, sqlol_parser.c, sqlol_and gram.y), since it
+ * requires the yyscanner struct to still be available.
+ */
+int
+sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner)
+{
+	int			pos;
+
+	if (location < 0)
+		return 0;				/* no-op if location is unknown */
+
+	/* Convert byte offset to character number */
+	pos = pg_mbstrlen_with_len(yyextra->scanbuf, location) + 1;
+	/* And pass it to the ereport mechanism */
+	return errposition(pos);
+}
+
+/*
+ * scanner_yyerror
+ *		Report a lexer or grammar error.
+ *
+ * Just ignore as we'll fallback to raw_parser().
+ */
+void
+sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner)
+{
+	return;
+}
+
+
+/*
+ * Called before any actual parsing is done
+ */
+sqlol_yyscan_t
+sqlol_scanner_init(const char *str,
+			 sqlol_yy_extra_type *yyext,
+			 const sqlol_ScanKeyword *keywords,
+			 int num_keywords)
+{
+	Size		slen = strlen(str);
+	yyscan_t	scanner;
+
+	if (yylex_init(&scanner) != 0)
+		elog(ERROR, "yylex_init() failed: %m");
+
+	sqlol_yyset_extra(yyext, scanner);
+
+	yyext->keywords = keywords;
+	yyext->num_keywords = num_keywords;
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	yyext->scanbuf = (char *) palloc(slen + 2);
+	yyext->scanbuflen = slen;
+	memcpy(yyext->scanbuf, str, slen);
+	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+
+	/* initialize literal buffer to a reasonable but expansible size */
+	yyext->literalalloc = 1024;
+	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
+	yyext->literallen = 0;
+
+	return scanner;
+}
+
+
+/*
+ * Called after parsing is done to clean up after scanner_init()
+ */
+void
+sqlol_scanner_finish(sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * We don't bother to call yylex_destroy(), because all it would do is
+	 * pfree a small amount of control storage.  It's cheaper to leak the
+	 * storage until the parsing context is destroyed.  The amount of space
+	 * involved is usually negligible compared to the output parse tree
+	 * anyway.
+	 *
+	 * We do bother to pfree the scanbuf and literal buffer, but only if they
+	 * represent a nontrivial amount of space.  The 8K cutoff is arbitrary.
+	 */
+	if (yyextra->scanbuflen >= 8192)
+		pfree(yyextra->scanbuf);
+	if (yyextra->literalalloc >= 8192)
+		pfree(yyextra->literalbuf);
+}
+
+
+static void
+addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + yleng) >= yyextra->literalalloc)
+	{
+		do
+		{
+			yyextra->literalalloc *= 2;
+		} while ((yyextra->literallen + yleng) >= yyextra->literalalloc);
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	memcpy(yyextra->literalbuf + yyextra->literallen, ytext, yleng);
+	yyextra->literallen += yleng;
+}
+
+
+static void
+addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + 1) >= yyextra->literalalloc)
+	{
+		yyextra->literalalloc *= 2;
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	yyextra->literalbuf[yyextra->literallen] = ychar;
+	yyextra->literallen += 1;
+}
+
+
+/*
+ * Create a palloc'd copy of literalbuf, adding a trailing null.
+ */
+static char *
+litbufdup(sqlol_yyscan_t yyscanner)
+{
+	int			llen = yyextra->literallen;
+	char	   *new;
+
+	new = palloc(llen + 1);
+	memcpy(new, yyextra->literalbuf, llen);
+	new[llen] = '\0';
+	return new;
+}
+
+/*
+ * Interface functions to make flex use palloc() instead of malloc().
+ * It'd be better to make these static, but flex insists otherwise.
+ */
+
+void *
+sqlol_yyalloc(yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	return palloc(bytes);
+}
+
+void *
+sqlol_yyrealloc(void *ptr, yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		return repalloc(ptr, bytes);
+	else
+		return palloc(bytes);
+}
+
+void
+sqlol_yyfree(void *ptr, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		pfree(ptr);
+}
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
new file mode 100644
index 0000000000..0a497e9d91
--- /dev/null
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -0,0 +1,118 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scanner.h
+ *		API for the core scanner (flex machine)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_scanner.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_SCANNER_H
+#define SQLOL_SCANNER_H
+
+#include "sqlol_keywords.h"
+
+/*
+ * The scanner returns extra data about scanned tokens in this union type.
+ * Note that this is a subset of the fields used in YYSTYPE of the bison
+ * parsers built atop the scanner.
+ */
+typedef union sqlol_YYSTYPE
+{
+	int			ival;			/* for integer literals */
+	char	   *str;			/* for identifiers and non-integer literals */
+	const char *keyword;		/* canonical spelling of keywords */
+} sqlol_YYSTYPE;
+
+/*
+ * We track token locations in terms of byte offsets from the start of the
+ * source string, not the column number/line number representation that
+ * bison uses by default.  Also, to minimize overhead we track only one
+ * location (usually the first token location) for each construct, not
+ * the beginning and ending locations as bison does by default.  It's
+ * therefore sufficient to make YYLTYPE an int.
+ */
+#define YYLTYPE  int
+
+/*
+ * Another important component of the scanner's API is the token code numbers.
+ * However, those are not defined in this file, because bison insists on
+ * defining them for itself.  The token codes used by the core scanner are
+ * the ASCII characters plus these:
+ *	%token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
+ *	%token <ival>	ICONST PARAM
+ *	%token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
+ *	%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+ * The above token definitions *must* be the first ones declared in any
+ * bison parser built atop this scanner, so that they will have consistent
+ * numbers assigned to them (specifically, IDENT = 258 and so on).
+ */
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.
+ * Private state needed by the core scanner goes here.  Note that the actual
+ * yy_extra struct may be larger and have this as its first component, thus
+ * allowing the calling parser to keep some fields of its own in YY_EXTRA.
+ */
+typedef struct sqlol_yy_extra_type
+{
+	/*
+	 * The string the scanner is physically scanning.  We keep this mainly so
+	 * that we can cheaply compute the offset of the current token (yytext).
+	 */
+	char	   *scanbuf;
+	Size		scanbuflen;
+
+	/*
+	 * The keyword list to use, and the associated grammar token codes.
+	 */
+	const sqlol_ScanKeyword *keywords;
+	int		num_keywords;
+
+	/*
+	 * literalbuf is used to accumulate literal values when multiple rules are
+	 * needed to parse a single literal.  Call startlit() to reset buffer to
+	 * empty, addlit() to add text.  NOTE: the string in literalbuf is NOT
+	 * necessarily null-terminated, but there always IS room to add a trailing
+	 * null at offset literallen.  We store a null only when we need it.
+	 */
+	char	   *literalbuf;		/* palloc'd expandable buffer */
+	int			literallen;		/* actual current string length */
+	int			literalalloc;	/* current allocated buffer size */
+
+	/*
+	 * Random assorted scanner state.
+	 */
+	int			state_before_str_stop;	/* start cond. before end quote */
+	YYLTYPE		save_yylloc;	/* one-element stack for PUSH_YYLLOC() */
+
+	/* state variables for literal-lexing warnings */
+	bool		saw_non_ascii;
+} sqlol_yy_extra_type;
+
+/*
+ * The type of yyscanner is opaque outside scan.l.
+ */
+typedef void *sqlol_yyscan_t;
+
+
+/* Constant data exported from parser/scan.l */
+extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
+
+/* Entry points in parser/scan.l */
+extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
+								  sqlol_yy_extra_type *yyext,
+								  const sqlol_ScanKeyword *keywords,
+								  int num_keywords);
+extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
+extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+extern int	sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner);
+extern void sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_SCANNER_H */
-- 
2.31.1

From b362e0238049009c586fdadb2fb53b2eb5dc6e3d Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 01:33:42 +0800
Subject: [PATCH v4 3/4] Add a new MODE_SINGLE_QUERY to the core parser and use
 it in pg_parse_query.

If a third-party module provides a parser_hook, pg_parse_query() switches to
single-query parsing so multi-query commands using different grammar can work
properly.  If the third-party module supports the full set of SQL we support,
or want to prevent fallback on the core parser, it can ignore the
MODE_SINGLE_QUERY mode and parse the full query string.  In that case they must
return a List with more than one RawStmt or a single RawStmt with a 0 length to
stop the parsing phase, or raise an ERROR.

Otherwise, plugins should parse a single query only and always return a List
containing a single RawStmt with a properly set length (possibly 0 if it was a
single query without end of query delimiter).  If the command is valid but
doesn't contain any statements (e.g. a single semi-colon), a single RawStmt
with a NULL stmt field should be returned, containing the consumed query string
length so we can move to the next command in a single pass rather than 1 byte
at a time.

Also, third-party modules can choose to ignore some or all of parsing error if
they want to implement only subset of postgres suppoted syntax, or even a
totally different syntax, and fall-back on core grammar for unhandled case.  In
thase case, they should set the error flag to true.  The returned List will be
ignored and the same offset of the input string will be parsed using the core
parser.

Finally, note that third-party plugins that wants to fallback on other grammar
should first try to call a previous parser hook if any before setting the error
switch and returning.
---
 .../pg_stat_statements/pg_stat_statements.c   |   3 +-
 src/backend/commands/tablecmds.c              |   2 +-
 src/backend/executor/spi.c                    |   4 +-
 src/backend/parser/gram.y                     |  29 +++-
 src/backend/parser/parse_type.c               |   2 +-
 src/backend/parser/parser.c                   |  15 +-
 src/backend/parser/scan.l                     |  26 +++-
 src/backend/tcop/postgres.c                   | 138 ++++++++++++++++--
 src/include/parser/parser.h                   |   5 +-
 src/include/parser/scanner.h                  |   6 +-
 src/include/tcop/tcopprot.h                   |   3 +-
 src/pl/plpgsql/src/pl_gram.y                  |   2 +-
 src/pl/plpgsql/src/pl_scanner.c               |   2 +-
 13 files changed, 210 insertions(+), 27 deletions(-)

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 09433c8c96..d852575613 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -2718,7 +2718,8 @@ fill_in_constant_lengths(JumbleState *jstate, const char *query,
 	yyscanner = scanner_init(query,
 							 &yyextra,
 							 &ScanKeywords,
-							 ScanKeywordTokens);
+							 ScanKeywordTokens,
+							 0);
 
 	/* we don't want to re-emit any escape string warnings */
 	yyextra.escape_string_warning = false;
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 028e8ac46b..284933c693 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -12677,7 +12677,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 	 * parse_analyze() or the rewriter, but instead we need to pass them
 	 * through parse_utilcmd.c to make them ready for execution.
 	 */
-	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT);
+	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT, 0);
 	querytree_list = NIL;
 	foreach(list_item, raw_parsetree_list)
 	{
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index b8bd05e894..f05b3ce9e7 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -2120,7 +2120,7 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Do parse analysis and rule rewrite for each raw parsetree, storing the
@@ -2228,7 +2228,7 @@ _SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Construct plancache entries, but don't do parse analysis yet.
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index eb24195438..911bb4d24b 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -626,7 +626,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
 %token <ival>	ICONST PARAM
 %token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
-%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS END_OF_FILE
 
 /*
  * If you want to make any keyword changes, update the keyword table in
@@ -753,6 +753,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token		MODE_PLPGSQL_ASSIGN1
 %token		MODE_PLPGSQL_ASSIGN2
 %token		MODE_PLPGSQL_ASSIGN3
+%token		MODE_SINGLE_QUERY
 
 
 /* Precedence: lowest to highest */
@@ -858,6 +859,32 @@ parse_toplevel:
 				pg_yyget_extra(yyscanner)->parsetree =
 					list_make1(makeRawStmt((Node *) n, 0));
 			}
+			| MODE_SINGLE_QUERY toplevel_stmt ';'
+			{
+				RawStmt *raw = makeRawStmt($2, 0);
+				updateRawStmtEnd(raw, @3 + 1);
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string and move to the next command.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(raw);
+				YYACCEPT;
+			}
+			/*
+			 * We need to explicitly look for EOF to parse non-semicolon
+			 * terminated statements in single query mode, as we could
+			 * otherwise successfully parse the beginning of an otherwise
+			 * invalid query.
+			 */
+			| MODE_SINGLE_QUERY toplevel_stmt END_OF_FILE
+			{
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(makeRawStmt($2, 0));
+				YYACCEPT;
+			}
 		;
 
 /*
diff --git a/src/backend/parser/parse_type.c b/src/backend/parser/parse_type.c
index abe131ebeb..e9a7b5d62a 100644
--- a/src/backend/parser/parse_type.c
+++ b/src/backend/parser/parse_type.c
@@ -746,7 +746,7 @@ typeStringToTypeName(const char *str)
 	ptserrcontext.previous = error_context_stack;
 	error_context_stack = &ptserrcontext;
 
-	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME);
+	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME, 0);
 
 	error_context_stack = ptserrcontext.previous;
 
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index 875de7ba28..23fd49e74c 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -37,17 +37,25 @@ static char *str_udeescape(const char *str, char escape,
  *
  * Returns a list of raw (un-analyzed) parse trees.  The contents of the
  * list have the form required by the specified RawParseMode.
+ *
+ * For all mode different from MODE_SINGLE_QUERY, caller should provide a 0
+ * offset as the whole input string should be parsed.  Otherwise, caller should
+ * provide the wanted offset in the input string, or -1 if no offset is
+ * required.
  */
 List *
-raw_parser(const char *str, RawParseMode mode)
+raw_parser(const char *str, RawParseMode mode, int offset)
 {
 	core_yyscan_t yyscanner;
 	base_yy_extra_type yyextra;
 	int			yyresult;
 
+	Assert((mode != RAW_PARSE_SINGLE_QUERY && offset == 0) ||
+			(mode == RAW_PARSE_SINGLE_QUERY && offset != 0));
+
 	/* initialize the flex scanner */
 	yyscanner = scanner_init(str, &yyextra.core_yy_extra,
-							 &ScanKeywords, ScanKeywordTokens);
+							 &ScanKeywords, ScanKeywordTokens, offset);
 
 	/* base_yylex() only needs us to initialize the lookahead token, if any */
 	if (mode == RAW_PARSE_DEFAULT)
@@ -61,7 +69,8 @@ raw_parser(const char *str, RawParseMode mode)
 			MODE_PLPGSQL_EXPR,	/* RAW_PARSE_PLPGSQL_EXPR */
 			MODE_PLPGSQL_ASSIGN1,	/* RAW_PARSE_PLPGSQL_ASSIGN1 */
 			MODE_PLPGSQL_ASSIGN2,	/* RAW_PARSE_PLPGSQL_ASSIGN2 */
-			MODE_PLPGSQL_ASSIGN3	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_PLPGSQL_ASSIGN3,	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_SINGLE_QUERY		/* RAW_PARSE_SINGLE_QUERY */
 		};
 
 		yyextra.have_lookahead = true;
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
index 9f9d8a1706..8ccbe95ac6 100644
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -1041,7 +1041,10 @@ other			.
 
 <<EOF>>			{
 					SET_YYLLOC();
-					yyterminate();
+					if (yyextra->return_eof)
+						return END_OF_FILE;
+					else
+						yyterminate();
 				}
 
 %%
@@ -1189,8 +1192,10 @@ core_yyscan_t
 scanner_init(const char *str,
 			 core_yy_extra_type *yyext,
 			 const ScanKeywordList *keywordlist,
-			 const uint16 *keyword_tokens)
+			 const uint16 *keyword_tokens,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -1213,13 +1218,28 @@ scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Note that pg_parse_query will set a -1 offset rather than 0 for the
+	 * first query of a possibly multi-query string if it wants us to return an
+	 * EOF token.
+	 */
+	yyext->return_eof = (offset != 0);
+
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	if (offset > 0)
+		state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index e941b59b85..9331628add 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -602,17 +602,137 @@ ProcessClientWriteInterrupt(bool blocked)
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list = NIL;
+	List		   *result = NIL;
+	int				stmt_len, offset;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	if (parser_hook)
-		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
-	else
-		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	stmt_len = 0; /* lazily computed when needed */
+	offset = 0;
+
+	while(true)
+	{
+		List *raw_parsetree_list;
+		RawStmt *raw;
+		bool	error = false;
+
+		/*----------------
+		 * Start parsing the input string.  If a third-party module provided a
+		 * parser_hook, we switch to single-query parsing so multi-query
+		 * commands using different grammar can work properly.
+		 * If the third-party modules support the full set of SQL we support,
+		 * or want to prevent fallback on the core parser, it can ignore the
+		 * RAW_PARSE_SINGLE_QUERY flag and parse the full query string.
+		 * In that case they must return a List with more than one RawStmt or a
+		 * single RawStmt with a 0 length to stop the parsing phase, or raise
+		 * an ERROR.
+		 *
+		 * Otherwise, plugins should parse a single query only and always
+		 * return a List containing a single RawStmt with a properly set length
+		 * (possibly 0 if it was a single query without end of query
+		 * delimiter).  If the command is valid but doesn't contain any
+		 * statements (e.g. a single semi-colon), a single RawStmt with a NULL
+		 * stmt field should be returned, containing the consumed query string
+		 * length so we can move to the next command in a single pass rather
+		 * than 1 byte at a time.
+		 *
+		 * Also, third-party modules can choose to ignore some or all of
+		 * parsing error if they want to implement only subset of postgres
+		 * suppoted syntax, or even a totally different syntax, and fall-back
+		 * on core grammar for unhandled case.  In thase case, they should set
+		 * the error flag to true.  The returned List will be ignored and the
+		 * same offset of the input string will be parsed using the core
+		 * parser.
+		 *
+		 * Finally, note that third-party modules that wants to fallback on
+		 * other grammar should first try to call a previous parser hook if any
+		 * before setting the error switch and returning .
+		 */
+		if (parser_hook)
+			raw_parsetree_list = (*parser_hook) (query_string,
+												 RAW_PARSE_SINGLE_QUERY,
+												 offset,
+												 &error);
+
+		/*
+		 * If a third-party module couldn't parse a single query or if no
+		 * third-party module is configured, fallback on core parser.
+		 */
+		if (error || !parser_hook)
+		{
+			/* Send a -1 offset to raw_parser to specify that it should
+			 * explicitly detect EOF during parsing.  scanner_init() will treat
+			 * it the same as a 0 offset.
+			 */
+			raw_parsetree_list = raw_parser(query_string,
+					error ? RAW_PARSE_SINGLE_QUERY : RAW_PARSE_DEFAULT,
+					(error && offset == 0) ? -1 : offset);
+		}
+
+		/*
+		 * If there are no third-party plugin, or none of the parsers found a
+		 * valid query, or if a third party module consumed the whole
+		 * query string we're done.
+		 */
+		if (!parser_hook || raw_parsetree_list == NIL ||
+			list_length(raw_parsetree_list) > 1)
+		{
+			/*
+			 * Warn third-party plugins if they mix "single query" and "whole
+			 * input string" strategy rather than silently accepting it and
+			 * maybe allow fallback on core grammar even if they want to avoid
+			 * that.  This way plugin authors can be warned early of the issue.
+			 */
+			if (result != NIL)
+			{
+				Assert(parser_hook != NULL);
+				elog(ERROR, "parser_hook should parse a single statement at "
+						"a time or consume the whole input string at once");
+			}
+			result = raw_parsetree_list;
+			break;
+		}
+
+		if (stmt_len == 0)
+			stmt_len = strlen(query_string);
+
+		raw = linitial_node(RawStmt, raw_parsetree_list);
+
+		/*
+		 * In single-query mode, the parser will return statement location info
+		 * relative to the beginning of complete original string, not the part
+		 * we just parsed, so adjust the location info.
+		 */
+		if (offset > 0 && raw->stmt_len > 0)
+		{
+			Assert(raw->stmt_len > offset);
+			raw->stmt_location = offset;
+			raw->stmt_len -= offset;
+		}
+
+		/* Ignore the statement if it didn't contain any command. */
+		if (raw->stmt)
+			result = lappend(result, raw);
+
+		if (raw->stmt_len == 0)
+		{
+			/* The statement was the whole string, we're done. */
+			break;
+		}
+		else if (raw->stmt_len + offset >= stmt_len)
+		{
+			/* We consumed all of the input string, we're done. */
+			break;
+		}
+		else
+		{
+			/* Advance the offset to the next command. */
+			offset += raw->stmt_len;
+		}
+	}
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
@@ -620,13 +740,13 @@ pg_parse_query(const char *query_string)
 #ifdef COPY_PARSE_PLAN_TREES
 	/* Optional debugging check: pass raw parsetrees through copyObject() */
 	{
-		List	   *new_list = copyObject(raw_parsetree_list);
+		List	   *new_list = copyObject(result);
 
 		/* This checks both copyObject() and the equal() routines... */
-		if (!equal(new_list, raw_parsetree_list))
+		if (!equal(new_list, result))
 			elog(WARNING, "copyObject() failed to produce an equal raw parse tree");
 		else
-			raw_parsetree_list = new_list;
+			result = new_list;
 	}
 #endif
 
@@ -638,7 +758,7 @@ pg_parse_query(const char *query_string)
 
 	TRACE_POSTGRESQL_QUERY_PARSE_DONE(query_string);
 
-	return raw_parsetree_list;
+	return result;
 }
 
 /*
diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h
index 853b0f1606..5694ae791a 100644
--- a/src/include/parser/parser.h
+++ b/src/include/parser/parser.h
@@ -41,7 +41,8 @@ typedef enum
 	RAW_PARSE_PLPGSQL_EXPR,
 	RAW_PARSE_PLPGSQL_ASSIGN1,
 	RAW_PARSE_PLPGSQL_ASSIGN2,
-	RAW_PARSE_PLPGSQL_ASSIGN3
+	RAW_PARSE_PLPGSQL_ASSIGN3,
+	RAW_PARSE_SINGLE_QUERY
 } RawParseMode;
 
 /* Values for the backslash_quote GUC */
@@ -59,7 +60,7 @@ extern PGDLLIMPORT bool standard_conforming_strings;
 
 
 /* Primary entry point for the raw parsing functions */
-extern List *raw_parser(const char *str, RawParseMode mode);
+extern List *raw_parser(const char *str, RawParseMode mode, int offset);
 
 /* Utility functions exported by gram.y (perhaps these should be elsewhere) */
 extern List *SystemFuncName(char *name);
diff --git a/src/include/parser/scanner.h b/src/include/parser/scanner.h
index 0d8182faa0..a2e97be5d5 100644
--- a/src/include/parser/scanner.h
+++ b/src/include/parser/scanner.h
@@ -113,6 +113,9 @@ typedef struct core_yy_extra_type
 	/* state variables for literal-lexing warnings */
 	bool		warn_on_first_escape;
 	bool		saw_non_ascii;
+
+	/* state variable for returning an EOF token in single query mode */
+	bool		return_eof;
 } core_yy_extra_type;
 
 /*
@@ -136,7 +139,8 @@ extern PGDLLIMPORT const uint16 ScanKeywordTokens[];
 extern core_yyscan_t scanner_init(const char *str,
 								  core_yy_extra_type *yyext,
 								  const ScanKeywordList *keywordlist,
-								  const uint16 *keyword_tokens);
+								  const uint16 *keyword_tokens,
+								  int offset);
 extern void scanner_finish(core_yyscan_t yyscanner);
 extern int	core_yylex(core_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   core_yyscan_t yyscanner);
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 131dc2b22e..27201dde1d 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -45,7 +45,8 @@ typedef enum
 extern PGDLLIMPORT int log_statement;
 
 /* Hook for plugins to get control in pg_parse_query() */
-typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode,
+								   int offset, bool *error);
 extern PGDLLIMPORT parser_hook_type parser_hook;
 
 extern List *pg_parse_query(const char *query_string);
diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y
index 3fcca43b90..e5a8a6477a 100644
--- a/src/pl/plpgsql/src/pl_gram.y
+++ b/src/pl/plpgsql/src/pl_gram.y
@@ -3656,7 +3656,7 @@ check_sql_expr(const char *stmt, RawParseMode parseMode, int location)
 	error_context_stack = &syntax_errcontext;
 
 	oldCxt = MemoryContextSwitchTo(plpgsql_compile_tmp_cxt);
-	(void) raw_parser(stmt, parseMode);
+	(void) raw_parser(stmt, parseMode, 0);
 	MemoryContextSwitchTo(oldCxt);
 
 	/* Restore former ereport callback */
diff --git a/src/pl/plpgsql/src/pl_scanner.c b/src/pl/plpgsql/src/pl_scanner.c
index e4c7a91ab5..a2886c42ec 100644
--- a/src/pl/plpgsql/src/pl_scanner.c
+++ b/src/pl/plpgsql/src/pl_scanner.c
@@ -587,7 +587,7 @@ plpgsql_scanner_init(const char *str)
 {
 	/* Start up the core scanner */
 	yyscanner = scanner_init(str, &core_yy,
-							 &ReservedPLKeywords, ReservedPLKeywordTokens);
+							 &ReservedPLKeywords, ReservedPLKeywordTokens, 0);
 
 	/*
 	 * scanorig points to the original string, which unlike the scanner's
-- 
2.31.1

From 346b336b959bec03e1e7dbb6827c1cfd150785ff Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 02:15:54 +0800
Subject: [PATCH v4 4/4] Teach sqlol to use the new MODE_SINGLE_QUERY parser
 mode.

This way multi-statements commands using both core parser and sqlol parser can
be supported.

Also add a LOLCODE version of CREATE VIEW viewname AS to easily test
multi-statements commands.
---
 contrib/sqlol/Makefile              |  2 +
 contrib/sqlol/expected/01_sqlol.out | 77 +++++++++++++++++++++++++++++
 contrib/sqlol/repro.sql             | 18 +++++++
 contrib/sqlol/sql/01_sqlol.sql      | 44 +++++++++++++++++
 contrib/sqlol/sqlol.c               | 24 +++++----
 contrib/sqlol/sqlol_gram.y          | 63 +++++++++++------------
 contrib/sqlol/sqlol_kwlist.h        |  1 +
 contrib/sqlol/sqlol_scan.l          | 13 ++++-
 contrib/sqlol/sqlol_scanner.h       |  3 +-
 9 files changed, 199 insertions(+), 46 deletions(-)
 create mode 100644 contrib/sqlol/expected/01_sqlol.out
 create mode 100644 contrib/sqlol/repro.sql
 create mode 100644 contrib/sqlol/sql/01_sqlol.sql

diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
index 3850ac3fce..eaf94801c2 100644
--- a/contrib/sqlol/Makefile
+++ b/contrib/sqlol/Makefile
@@ -6,6 +6,8 @@ OBJS = \
 	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
 PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
 
+REGRESS = 01_sqlol
+
 sqlol_gram.h: sqlol_gram.c
 	touch $@
 
diff --git a/contrib/sqlol/expected/01_sqlol.out b/contrib/sqlol/expected/01_sqlol.out
new file mode 100644
index 0000000000..9c51dd62c2
--- /dev/null
+++ b/contrib/sqlol/expected/01_sqlol.out
@@ -0,0 +1,77 @@
+LOAD 'sqlol';
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+ id | val 
+----+-----
+(0 rows)
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+ ?column? 
+----------
+        3
+(1 row)
+
+-- test empty statement ignoring
+\;\;select 1 \g
+ ?column? 
+----------
+        1
+(1 row)
+
+-- check the created views
+SELECT relname, relkind
+FROM pg_class c
+JOIN pg_namespace n ON c.relnamespace = n.oid
+WHERE nspname = 'public'
+ORDER BY relname COLLATE "C";
+ relname | relkind 
+---------+---------
+ t1      | r
+ v0      | v
+ v1      | v
+ v2      | v
+ v3      | v
+ v4      | v
+ v5      | v
+(7 rows)
+
+--
+-- Error position
+--
+SELECT 1\;err;
+ERROR:  syntax error at or near "err"
+LINE 1: SELECT 1;err;
+                 ^
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+ERROR:  syntax error at or near "HAI"
+LINE 1: SELECT 1;HAI 1.2 I HAS A t1 GIMME id KTHXBYE
+                 ^
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+ERROR:  improper qualified name (too many dotted names): some.thing.public.t1
+LINE 1: SELECT 1;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHX...
+                                 ^
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
+ERROR:  relation "notatable" does not exist
+LINE 1: SELECT 1;SELECT * FROM notatable;
+                               ^
diff --git a/contrib/sqlol/repro.sql b/contrib/sqlol/repro.sql
new file mode 100644
index 0000000000..0ebcb53160
--- /dev/null
+++ b/contrib/sqlol/repro.sql
@@ -0,0 +1,18 @@
+DROP TABLE IF EXISTS t1 CASCADE;
+
+LOAD 'sqlol';
+
+\;\; SELECT 1\;
+
+CREATE TABLE t1 (id integer, val text);
+
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+SELECT 1\;SELECT 2\;SELECT 3 \g
+\d
diff --git a/contrib/sqlol/sql/01_sqlol.sql b/contrib/sqlol/sql/01_sqlol.sql
new file mode 100644
index 0000000000..e89a3dd9a0
--- /dev/null
+++ b/contrib/sqlol/sql/01_sqlol.sql
@@ -0,0 +1,44 @@
+LOAD 'sqlol';
+
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+
+-- test empty statement ignoring
+\;\;select 1 \g
+
+-- check the created views
+SELECT relname, relkind
+FROM pg_class c
+JOIN pg_namespace n ON c.relnamespace = n.oid
+WHERE nspname = 'public'
+ORDER BY relname COLLATE "C";
+
+--
+-- Error position
+--
+SELECT 1\;err;
+
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
index b986966181..7d4e1b631f 100644
--- a/contrib/sqlol/sqlol.c
+++ b/contrib/sqlol/sqlol.c
@@ -26,7 +26,8 @@ static parser_hook_type prev_parser_hook = NULL;
 void		_PG_init(void);
 void		_PG_fini(void);
 
-static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+static List *sqlol_parser_hook(const char *str, RawParseMode mode, int offset,
+							   bool *error);
 
 
 /*
@@ -54,23 +55,25 @@ _PG_fini(void)
  * sqlol_parser_hook: parse our grammar
  */
 static List *
-sqlol_parser_hook(const char *str, RawParseMode mode)
+sqlol_parser_hook(const char *str, RawParseMode mode, int offset, bool *error)
 {
 	sqlol_yyscan_t yyscanner;
 	sqlol_base_yy_extra_type yyextra;
 	int			yyresult;
 
-	if (mode != RAW_PARSE_DEFAULT)
+	if (mode != RAW_PARSE_DEFAULT && mode != RAW_PARSE_SINGLE_QUERY)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	/* initialize the flex scanner */
 	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
-							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords,
+							 offset);
 
 	/* initialize the bison parser */
 	sqlol_parser_init(&yyextra);
@@ -88,9 +91,10 @@ sqlol_parser_hook(const char *str, RawParseMode mode)
 	if (yyresult)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	return yyextra.parsetree;
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
index 64d00d14ca..4c36cfef5e 100644
--- a/contrib/sqlol/sqlol_gram.y
+++ b/contrib/sqlol/sqlol_gram.y
@@ -20,6 +20,7 @@
 
 #include "catalog/namespace.h"
 #include "nodes/makefuncs.h"
+#include "catalog/pg_class_d.h"
 
 #include "sqlol_gramparse.h"
 
@@ -106,10 +107,10 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
 	ResTarget			*target;
 }
 
-%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+%type <node>	stmt toplevel_stmt GimmehStmt MaekStmt simple_gimmeh columnref
 				indirection_el
 
-%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+%type <list>	parse_toplevel rawstmt gimmeh_list indirection
 
 %type <range>	qualified_name
 
@@ -134,22 +135,19 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
  */
 
 /* ordinary key words in alphabetical order */
-%token <keyword> A GIMMEH HAI HAS I KTHXBYE
-
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE MAEK
 
 %%
 
 /*
  *	The target production for the whole parse.
- *
- * Ordinarily we parse a list of statements, but if we see one of the
- * special MODE_XXX symbols as first token, we parse something else.
- * The options here correspond to enum RawParseMode, which see for details.
  */
 parse_toplevel:
-			stmtmulti
+			rawstmt
 			{
 				pg_yyget_extra(yyscanner)->parsetree = $1;
+
+				YYACCEPT;
 			}
 		;
 
@@ -163,24 +161,11 @@ parse_toplevel:
  * we'd get -1 for the location in such cases.
  * We also take care to discard empty statements entirely.
  */
-stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
-				{
-					if ($1 != NIL)
-					{
-						/* update length of previous stmt */
-						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
-					}
-					if ($3 != NULL)
-						$$ = lappend($1, makeRawStmt($3, @2 + 1));
-					else
-						$$ = $1;
-				}
-			| toplevel_stmt
+rawstmt:	toplevel_stmt KTHXBYE
 				{
-					if ($1 != NULL)
-						$$ = list_make1(makeRawStmt($1, 0));
-					else
-						$$ = NIL;
+					RawStmt *raw = makeRawStmt($1, 0);
+					updateRawStmtEnd(raw, @2 + 7);
+					$$ = list_make1(raw);
 				}
 		;
 
@@ -189,13 +174,12 @@ stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
  * those words have different meanings in function bodys.
  */
 toplevel_stmt:
-			stmt
+			HAI FCONST stmt { $$ = $3; }
 		;
 
 stmt:
 			GimmehStmt
-			| /*EMPTY*/
-				{ $$ = NULL; }
+			| MaekStmt
 		;
 
 /*****************************************************************************
@@ -209,12 +193,11 @@ GimmehStmt:
 		;
 
 simple_gimmeh:
-			HAI FCONST I HAS A qualified_name
-			GIMMEH gimmeh_list
+			I HAS A qualified_name GIMMEH gimmeh_list
 				{
 					SelectStmt *n = makeNode(SelectStmt);
-					n->targetList = $8;
-					n->fromClause = list_make1($6);
+					n->targetList = $6;
+					n->fromClause = list_make1($4);
 					$$ = (Node *)n;
 				}
 		;
@@ -233,6 +216,20 @@ gimmeh_el:
 				$$->location = @1;
 			}
 
+MaekStmt:
+		MAEK GimmehStmt A qualified_name
+			{
+				ViewStmt *n = makeNode(ViewStmt);
+				n->view = $4;
+				n->view->relpersistence = RELPERSISTENCE_PERMANENT;
+				n->aliases = NIL;
+				n->query = $2;
+				n->replace = false;
+				n->options = NIL;
+				n->withCheckOption = false;
+				$$ = (Node *) n;
+			}
+
 qualified_name:
 			ColId
 				{
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
index 2de3893ee4..8b50d88df9 100644
--- a/contrib/sqlol/sqlol_kwlist.h
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -19,3 +19,4 @@ PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
 PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
 PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
 PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
+PG_KEYWORD("maek", MAEK, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
index a7088b8390..e6d4d53446 100644
--- a/contrib/sqlol/sqlol_scan.l
+++ b/contrib/sqlol/sqlol_scan.l
@@ -412,8 +412,10 @@ sqlol_yyscan_t
 sqlol_scanner_init(const char *str,
 			 sqlol_yy_extra_type *yyext,
 			 const sqlol_ScanKeyword *keywords,
-			 int num_keywords)
+			 int num_keywords,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -432,13 +434,20 @@ sqlol_scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
index 0a497e9d91..57f95867ee 100644
--- a/contrib/sqlol/sqlol_scanner.h
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -108,7 +108,8 @@ extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
 extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
 								  sqlol_yy_extra_type *yyext,
 								  const sqlol_ScanKeyword *keywords,
-								  int num_keywords);
+								  int num_keywords,
+								  int offset);
 extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
 extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   sqlol_yyscan_t yyscanner);
-- 
2.31.1

From 00644b3ec87c11fa4c4a1215ed79238e1407cd29 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 22:47:18 +0800
Subject: [PATCH v5 1/4] Add a parser_hook hook.

This does nothing but allow third-party plugins to implement a different
syntax, and fallback on the core parser if they don't implement a superset of
the supported core syntax.
---
 src/backend/tcop/postgres.c | 16 ++++++++++++++--
 src/include/tcop/tcopprot.h |  5 +++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 3f9ed549f9..66ee58a4b1 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -99,6 +99,9 @@ int			log_statement = LOGSTMT_NONE;
 /* GUC variable for maximum stack depth (measured in kilobytes) */
 int			max_stack_depth = 100;
 
+/* Hook for plugins to get control in pg_parse_query() */
+parser_hook_type parser_hook = NULL;
+
 /* wait N seconds to allow attach from a debugger */
 int			PostAuthDelay = 0;
 
@@ -589,18 +592,27 @@ ProcessClientWriteInterrupt(bool blocked)
  * database tables.  So, we rely on the raw parser to determine whether
  * we've seen a COMMIT or ABORT command; when we are in abort state, other
  * commands are not processed any further than the raw parse stage.
+ *
+ * To support loadable plugins that monitor the parsing or implements SQL
+ * syntactic sugar we provide a hook variable that lets a plugin get control
+ * before and after the standard parsing process.  If the plugin only implement
+ * a subset of postgres supported syntax, it's its duty to call raw_parser (or
+ * the previous hook if any) for the statements it doesn't understand.
  */
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list;
+	List	   *raw_parsetree_list = NIL;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	if (parser_hook)
+		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
+	else
+		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 968345404e..131dc2b22e 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -17,6 +17,7 @@
 #include "nodes/params.h"
 #include "nodes/parsenodes.h"
 #include "nodes/plannodes.h"
+#include "parser/parser.h"
 #include "storage/procsignal.h"
 #include "utils/guc.h"
 #include "utils/queryenvironment.h"
@@ -43,6 +44,10 @@ typedef enum
 
 extern PGDLLIMPORT int log_statement;
 
+/* Hook for plugins to get control in pg_parse_query() */
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+extern PGDLLIMPORT parser_hook_type parser_hook;
+
 extern List *pg_parse_query(const char *query_string);
 extern List *pg_rewrite_query(Query *query);
 extern List *pg_analyze_and_rewrite(RawStmt *parsetree,
-- 
2.32.0

From a8815ab1cfdd29a5ae77bfff92279e25d7c380db Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Wed, 21 Apr 2021 23:54:02 +0800
Subject: [PATCH v5 2/4] Add a sqlol parser.

This is a toy example of alternative grammar that only accept a LOLCODE
compatible version of a

SELECT [column, ] column FROM tablename

and fallback on the core parser for everything else.
---
 contrib/Makefile                |   1 +
 contrib/sqlol/.gitignore        |   7 +
 contrib/sqlol/Makefile          |  33 ++
 contrib/sqlol/sqlol.c           | 107 +++++++
 contrib/sqlol/sqlol_gram.y      | 439 ++++++++++++++++++++++++++
 contrib/sqlol/sqlol_gramparse.h |  61 ++++
 contrib/sqlol/sqlol_keywords.c  |  97 ++++++
 contrib/sqlol/sqlol_keywords.h  |  38 +++
 contrib/sqlol/sqlol_kwlist.h    |  21 ++
 contrib/sqlol/sqlol_scan.l      | 544 ++++++++++++++++++++++++++++++++
 contrib/sqlol/sqlol_scanner.h   | 118 +++++++
 11 files changed, 1466 insertions(+)
 create mode 100644 contrib/sqlol/.gitignore
 create mode 100644 contrib/sqlol/Makefile
 create mode 100644 contrib/sqlol/sqlol.c
 create mode 100644 contrib/sqlol/sqlol_gram.y
 create mode 100644 contrib/sqlol/sqlol_gramparse.h
 create mode 100644 contrib/sqlol/sqlol_keywords.c
 create mode 100644 contrib/sqlol/sqlol_keywords.h
 create mode 100644 contrib/sqlol/sqlol_kwlist.h
 create mode 100644 contrib/sqlol/sqlol_scan.l
 create mode 100644 contrib/sqlol/sqlol_scanner.h

diff --git a/contrib/Makefile b/contrib/Makefile
index f27e458482..2a80cd137b 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -43,6 +43,7 @@ SUBDIRS = \
 		postgres_fdw	\
 		seg		\
 		spi		\
+		sqlol		\
 		tablefunc	\
 		tcn		\
 		test_decoding	\
diff --git a/contrib/sqlol/.gitignore b/contrib/sqlol/.gitignore
new file mode 100644
index 0000000000..3c4b587792
--- /dev/null
+++ b/contrib/sqlol/.gitignore
@@ -0,0 +1,7 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
+sqlol_gram.c
+sqlol_gram.h
+sqlol_scan.c
diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
new file mode 100644
index 0000000000..3850ac3fce
--- /dev/null
+++ b/contrib/sqlol/Makefile
@@ -0,0 +1,33 @@
+# contrib/sqlol/Makefile
+
+MODULE_big = sqlol
+OBJS = \
+	$(WIN32RES) \
+	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
+PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
+
+sqlol_gram.h: sqlol_gram.c
+	touch $@
+
+sqlol_gram.c: BISONFLAGS += -d
+# sqlol_gram.c: BISON_CHECK_CMD = $(PERL) $(srcdir)/check_keywords.pl $< $(top_srcdir)/src/include/parser/kwlist.h
+
+
+sqlol_scan.c: FLEXFLAGS = -CF -p -p
+sqlol_scan.c: FLEX_NO_BACKUP=yes
+sqlol_scan.c: FLEX_FIX_WARNING=yes
+
+
+# Force these dependencies to be known even without dependency info built:
+sqlol.o sqlol_gram.o sqlol_scan.o parser.o: sqlol_gram.h
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/sqlol
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
new file mode 100644
index 0000000000..b986966181
--- /dev/null
+++ b/contrib/sqlol/sqlol.c
@@ -0,0 +1,107 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol.c
+ *
+ *
+ * Copyright (c) 2008-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "tcop/tcopprot.h"
+
+#include "sqlol_gramparse.h"
+#include "sqlol_keywords.h"
+
+PG_MODULE_MAGIC;
+
+
+/* Saved hook values in case of unload */
+static parser_hook_type prev_parser_hook = NULL;
+
+void		_PG_init(void);
+void		_PG_fini(void);
+
+static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+
+
+/*
+ * Module load callback
+ */
+void
+_PG_init(void)
+{
+	/* Install hooks. */
+	prev_parser_hook = parser_hook;
+	parser_hook = sqlol_parser_hook;
+}
+
+/*
+ * Module unload callback
+ */
+void
+_PG_fini(void)
+{
+	/* Uninstall hooks. */
+	parser_hook = prev_parser_hook;
+}
+
+/*
+ * sqlol_parser_hook: parse our grammar
+ */
+static List *
+sqlol_parser_hook(const char *str, RawParseMode mode)
+{
+	sqlol_yyscan_t yyscanner;
+	sqlol_base_yy_extra_type yyextra;
+	int			yyresult;
+
+	if (mode != RAW_PARSE_DEFAULT)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	/* initialize the flex scanner */
+	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+
+	/* initialize the bison parser */
+	sqlol_parser_init(&yyextra);
+
+	/* Parse! */
+	yyresult = sqlol_base_yyparse(yyscanner);
+
+	/* Clean up (release memory) */
+	sqlol_scanner_finish(yyscanner);
+
+	/*
+	 * Invalid statement, fallback on previous parser_hook if any or
+	 * raw_parser()
+	 */
+	if (yyresult)
+	{
+		if (prev_parser_hook)
+			return (*prev_parser_hook) (str, mode);
+		else
+			return raw_parser(str, mode);
+	}
+
+	return yyextra.parsetree;
+}
+
+int
+sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, sqlol_yyscan_t yyscanner)
+{
+	int			cur_token;
+
+	cur_token = sqlol_yylex(&(lvalp->sqlol_yystype), llocp, yyscanner);
+
+	return cur_token;
+}
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
new file mode 100644
index 0000000000..3214865a53
--- /dev/null
+++ b/contrib/sqlol/sqlol_gram.y
@@ -0,0 +1,439 @@
+%{
+
+/*#define YYDEBUG 1*/
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gram.y
+ *	  sqlol BISON rules/actions
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_gram.y
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "catalog/namespace.h"
+#include "nodes/makefuncs.h"
+
+#include "sqlol_gramparse.h"
+
+/*
+ * Location tracking support --- simpler than bison's default, since we only
+ * want to track the start position not the end position of each nonterminal.
+ */
+#define YYLLOC_DEFAULT(Current, Rhs, N) \
+	do { \
+		if ((N) > 0) \
+			(Current) = (Rhs)[1]; \
+		else \
+			(Current) = (-1); \
+	} while (0)
+
+/*
+ * The above macro assigns -1 (unknown) as the parse location of any
+ * nonterminal that was reduced from an empty rule, or whose leftmost
+ * component was reduced from an empty rule.  This is problematic
+ * for nonterminals defined like
+ *		OptFooList: / * EMPTY * / { ... } | OptFooList Foo { ... } ;
+ * because we'll set -1 as the location during the first reduction and then
+ * copy it during each subsequent reduction, leaving us with -1 for the
+ * location even when the list is not empty.  To fix that, do this in the
+ * action for the nonempty rule(s):
+ *		if (@$ < 0) @$ = @2;
+ * (Although we have many nonterminals that follow this pattern, we only
+ * bother with fixing @$ like this when the nonterminal's parse location
+ * is actually referenced in some rule.)
+ *
+ * A cleaner answer would be to make YYLLOC_DEFAULT scan all the Rhs
+ * locations until it's found one that's not -1.  Then we'd get a correct
+ * location for any nonterminal that isn't entirely empty.  But this way
+ * would add overhead to every rule reduction, and so far there's not been
+ * a compelling reason to pay that overhead.
+ */
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+
+#define parser_yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+#define parser_errposition(pos)  sqlol_scanner_errposition(pos, yyscanner)
+
+static void sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner,
+						 const char *msg);
+static RawStmt *makeRawStmt(Node *stmt, int stmt_location);
+static void updateRawStmtEnd(RawStmt *rs, int end_location);
+static Node *makeColumnRef(char *colname, List *indirection,
+						   int location, sqlol_yyscan_t yyscanner);
+static void check_qualified_name(List *names, sqlol_yyscan_t yyscanner);
+static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
+
+%}
+
+%pure-parser
+%expect 0
+%name-prefix="sqlol_base_yy"
+%locations
+
+%parse-param {sqlol_yyscan_t yyscanner}
+%lex-param   {sqlol_yyscan_t yyscanner}
+
+%union
+{
+	sqlol_YYSTYPE		sqlol_yystype;
+	/* these fields must match sqlol_YYSTYPE: */
+	int					ival;
+	char				*str;
+	const char			*keyword;
+
+	List				*list;
+	Node				*node;
+	RangeVar			*range;
+	ResTarget			*target;
+}
+
+%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+				indirection_el
+
+%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+
+%type <range>	qualified_name
+
+%type <str>		ColId ColLabel attr_name
+
+%type <target>	gimmeh_el
+
+/*
+ * Non-keyword token types.  These are hard-wired into the "flex" lexer.
+ * They must be listed first so that their numeric codes do not depend on
+ * the set of keywords.  PL/pgSQL depends on this so that it can share the
+ * same lexer.  If you add/change tokens here, fix PL/pgSQL to match!
+ *
+ */
+%token <str>	IDENT FCONST SCONST Op
+
+/*
+ * If you want to make any keyword changes, update the keyword table in
+ * src/include/parser/kwlist.h and add new keywords to the appropriate one
+ * of the reserved-or-not-so-reserved keyword lists, below; search
+ * this file for "Keyword category lists".
+ */
+
+/* ordinary key words in alphabetical order */
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE
+
+
+%%
+
+/*
+ *	The target production for the whole parse.
+ *
+ * Ordinarily we parse a list of statements, but if we see one of the
+ * special MODE_XXX symbols as first token, we parse something else.
+ * The options here correspond to enum RawParseMode, which see for details.
+ */
+parse_toplevel:
+			stmtmulti
+			{
+				pg_yyget_extra(yyscanner)->parsetree = $1;
+			}
+		;
+
+/*
+ * At top level, we wrap each stmt with a RawStmt node carrying start location
+ * and length of the stmt's text.  Notice that the start loc/len are driven
+ * entirely from semicolon locations (@2).  It would seem natural to use
+ * @1 or @3 to get the true start location of a stmt, but that doesn't work
+ * for statements that can start with empty nonterminals (opt_with_clause is
+ * the main offender here); as noted in the comments for YYLLOC_DEFAULT,
+ * we'd get -1 for the location in such cases.
+ * We also take care to discard empty statements entirely.
+ */
+stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
+				{
+					if ($1 != NIL)
+					{
+						/* update length of previous stmt */
+						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
+					}
+					if ($3 != NULL)
+						$$ = lappend($1, makeRawStmt($3, @2 + 1));
+					else
+						$$ = $1;
+				}
+			| toplevel_stmt
+				{
+					if ($1 != NULL)
+						$$ = list_make1(makeRawStmt($1, 0));
+					else
+						$$ = NIL;
+				}
+		;
+
+/*
+ * toplevel_stmt includes BEGIN and END.  stmt does not include them, because
+ * those words have different meanings in function bodys.
+ */
+toplevel_stmt:
+			stmt
+		;
+
+stmt:
+			GimmehStmt
+			| /*EMPTY*/
+				{ $$ = NULL; }
+		;
+
+/*****************************************************************************
+ *
+ * GIMMEH statement
+ *
+ *****************************************************************************/
+
+GimmehStmt:
+			simple_gimmeh						{ $$ = $1; }
+		;
+
+simple_gimmeh:
+			HAI FCONST I HAS A qualified_name
+			GIMMEH gimmeh_list
+				{
+					SelectStmt *n = makeNode(SelectStmt);
+					n->targetList = $8;
+					n->fromClause = list_make1($6);
+					$$ = (Node *)n;
+				}
+		;
+
+gimmeh_list:
+		   gimmeh_el							{ $$ = list_make1($1); }
+		   | gimmeh_list ',' gimmeh_el			{ $$ = lappend($1, $3); }
+
+gimmeh_el:
+		 columnref
+			{
+				$$ = makeNode(ResTarget);
+				$$->name = NULL;
+				$$->indirection = NIL;
+				$$->val = (Node *)$1;
+				$$->location = @1;
+			}
+
+qualified_name:
+			ColId
+				{
+					$$ = makeRangeVar(NULL, $1, @1);
+				}
+			| ColId indirection
+				{
+					check_qualified_name($2, yyscanner);
+					$$ = makeRangeVar(NULL, NULL, @1);
+					switch (list_length($2))
+					{
+						case 1:
+							$$->catalogname = NULL;
+							$$->schemaname = $1;
+							$$->relname = strVal(linitial($2));
+							break;
+						case 2:
+							$$->catalogname = $1;
+							$$->schemaname = strVal(linitial($2));
+							$$->relname = strVal(lsecond($2));
+							break;
+						default:
+							/*
+							 * It's ok to error out here as at this point we
+							 * already parsed a "HAI FCONST" preamble, and no
+							 * other grammar is likely to accept a command
+							 * starting with that, so there's no point trying
+							 * to fall back on the other grammars.
+							 */
+							ereport(ERROR,
+									(errcode(ERRCODE_SYNTAX_ERROR),
+									 errmsg("improper qualified name (too many dotted names): %s",
+											NameListToString(lcons(makeString($1), $2))),
+									 parser_errposition(@1)));
+							break;
+					}
+				}
+		;
+
+columnref:	ColId
+				{
+					$$ = makeColumnRef($1, NIL, @1, yyscanner);
+				}
+			| ColId indirection
+				{
+					$$ = makeColumnRef($1, $2, @1, yyscanner);
+				}
+		;
+
+ColId:		IDENT									{ $$ = $1; }
+
+indirection:
+			indirection_el							{ $$ = list_make1($1); }
+			| indirection indirection_el			{ $$ = lappend($1, $2); }
+		;
+
+indirection_el:
+			'.' attr_name
+				{
+					$$ = (Node *) makeString($2);
+				}
+		;
+
+attr_name:	ColLabel								{ $$ = $1; };
+
+ColLabel:	IDENT									{ $$ = $1; }
+
+%%
+
+/*
+ * The signature of this function is required by bison.  However, we
+ * ignore the passed yylloc and instead use the last token position
+ * available from the scanner.
+ */
+static void
+sqlol_base_yyerror(YYLTYPE *yylloc, sqlol_yyscan_t yyscanner, const char *msg)
+{
+	parser_yyerror(msg);
+}
+
+static RawStmt *
+makeRawStmt(Node *stmt, int stmt_location)
+{
+	RawStmt    *rs = makeNode(RawStmt);
+
+	rs->stmt = stmt;
+	rs->stmt_location = stmt_location;
+	rs->stmt_len = 0;			/* might get changed later */
+	return rs;
+}
+
+/* Adjust a RawStmt to reflect that it doesn't run to the end of the string */
+static void
+updateRawStmtEnd(RawStmt *rs, int end_location)
+{
+	/*
+	 * If we already set the length, don't change it.  This is for situations
+	 * like "select foo ;; select bar" where the same statement will be last
+	 * in the string for more than one semicolon.
+	 */
+	if (rs->stmt_len > 0)
+		return;
+
+	/* OK, update length of RawStmt */
+	rs->stmt_len = end_location - rs->stmt_location;
+}
+
+static Node *
+makeColumnRef(char *colname, List *indirection,
+			  int location, sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * Generate a ColumnRef node, with an A_Indirection node added if there
+	 * is any subscripting in the specified indirection list.  However,
+	 * any field selection at the start of the indirection list must be
+	 * transposed into the "fields" part of the ColumnRef node.
+	 */
+	ColumnRef  *c = makeNode(ColumnRef);
+	int		nfields = 0;
+	ListCell *l;
+
+	c->location = location;
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Indices))
+		{
+			A_Indirection *i = makeNode(A_Indirection);
+
+			if (nfields == 0)
+			{
+				/* easy case - all indirection goes to A_Indirection */
+				c->fields = list_make1(makeString(colname));
+				i->indirection = check_indirection(indirection, yyscanner);
+			}
+			else
+			{
+				/* got to split the list in two */
+				i->indirection = check_indirection(list_copy_tail(indirection,
+																  nfields),
+												   yyscanner);
+				indirection = list_truncate(indirection, nfields);
+				c->fields = lcons(makeString(colname), indirection);
+			}
+			i->arg = (Node *) c;
+			return (Node *) i;
+		}
+		else if (IsA(lfirst(l), A_Star))
+		{
+			/* We only allow '*' at the end of a ColumnRef */
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+		nfields++;
+	}
+	/* No subscripting, so all indirection gets added to field list */
+	c->fields = lcons(makeString(colname), indirection);
+	return (Node *) c;
+}
+
+/* check_qualified_name --- check the result of qualified_name production
+ *
+ * It's easiest to let the grammar production for qualified_name allow
+ * subscripts and '*', which we then must reject here.
+ */
+static void
+check_qualified_name(List *names, sqlol_yyscan_t yyscanner)
+{
+	ListCell   *i;
+
+	foreach(i, names)
+	{
+		if (!IsA(lfirst(i), String))
+			parser_yyerror("syntax error");
+	}
+}
+
+/* check_indirection --- check the result of indirection production
+ *
+ * We only allow '*' at the end of the list, but it's hard to enforce that
+ * in the grammar, so do it here.
+ */
+static List *
+check_indirection(List *indirection, sqlol_yyscan_t yyscanner)
+{
+	ListCell *l;
+
+	foreach(l, indirection)
+	{
+		if (IsA(lfirst(l), A_Star))
+		{
+			if (lnext(indirection, l) != NULL)
+				parser_yyerror("improper use of \"*\"");
+		}
+	}
+	return indirection;
+}
+
+/* sqlol_parser_init()
+ * Initialize to parse one query string
+ */
+void
+sqlol_parser_init(sqlol_base_yy_extra_type *yyext)
+{
+	yyext->parsetree = NIL;		/* in case grammar forgets to set it */
+}
diff --git a/contrib/sqlol/sqlol_gramparse.h b/contrib/sqlol/sqlol_gramparse.h
new file mode 100644
index 0000000000..58233a8d87
--- /dev/null
+++ b/contrib/sqlol/sqlol_gramparse.h
@@ -0,0 +1,61 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_gramparse.h
+ *		Shared definitions for the "raw" parser (flex and bison phases only)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_gramparse.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_GRAMPARSE_H
+#define SQLOL_GRAMPARSE_H
+
+#include "nodes/parsenodes.h"
+#include "sqlol_scanner.h"
+
+/*
+ * NB: include gram.h only AFTER including scanner.h, because scanner.h
+ * is what #defines YYLTYPE.
+ */
+#include "sqlol_gram.h"
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.  Private
+ * state needed for raw parsing/lexing goes here.
+ */
+typedef struct sqlol_base_yy_extra_type
+{
+	/*
+	 * Fields used by the core scanner.
+	 */
+	sqlol_yy_extra_type sqlol_yy_extra;
+
+	/*
+	 * State variables that belong to the grammar.
+	 */
+	List	   *parsetree;		/* final parse result is delivered here */
+} sqlol_base_yy_extra_type;
+
+/*
+ * In principle we should use yyget_extra() to fetch the yyextra field
+ * from a yyscanner struct.  However, flex always puts that field first,
+ * and this is sufficiently performance-critical to make it seem worth
+ * cheating a bit to use an inline macro.
+ */
+#define pg_yyget_extra(yyscanner) (*((sqlol_base_yy_extra_type **) (yyscanner)))
+
+
+/* from parser.c */
+extern int	sqlol_base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+
+/* from gram.y */
+extern void sqlol_parser_init(sqlol_base_yy_extra_type *yyext);
+extern int	sqlol_baseyyparse(sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_GRAMPARSE_H */
diff --git a/contrib/sqlol/sqlol_keywords.c b/contrib/sqlol/sqlol_keywords.c
new file mode 100644
index 0000000000..ee51f423ac
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.c
@@ -0,0 +1,97 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.c
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  sqlol/sqlol_keywords.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "sqlol_gramparse.h"
+
+#define PG_KEYWORD(a,b,c) {a,b,c},
+
+const sqlol_ScanKeyword sqlol_ScanKeywords[] = {
+#include "sqlol_kwlist.h"
+};
+
+const int	sqlol_NumScanKeywords = lengthof(sqlol_ScanKeywords);
+
+#undef PG_KEYWORD
+
+
+/*
+ * ScanKeywordLookup - see if a given word is a keyword
+ *
+ * The table to be searched is passed explicitly, so that this can be used
+ * to search keyword lists other than the standard list appearing above.
+ *
+ * Returns a pointer to the sqlol_ScanKeyword table entry, or NULL if no match.
+ *
+ * The match is done case-insensitively.  Note that we deliberately use a
+ * dumbed-down case conversion that will only translate 'A'-'Z' into 'a'-'z',
+ * even if we are in a locale where tolower() would produce more or different
+ * translations.  This is to conform to the SQL99 spec, which says that
+ * keywords are to be matched in this way even though non-keyword identifiers
+ * receive a different case-normalization mapping.
+ */
+const sqlol_ScanKeyword *
+sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords)
+{
+	int			len,
+				i;
+	char		word[NAMEDATALEN];
+	const sqlol_ScanKeyword *low;
+	const sqlol_ScanKeyword *high;
+
+	len = strlen(text);
+	/* We assume all keywords are shorter than NAMEDATALEN. */
+	if (len >= NAMEDATALEN)
+		return NULL;
+
+	/*
+	 * Apply an ASCII-only downcasing.  We must not use tolower() since it may
+	 * produce the wrong translation in some locales (eg, Turkish).
+	 */
+	for (i = 0; i < len; i++)
+	{
+		char		ch = text[i];
+
+		if (ch >= 'A' && ch <= 'Z')
+			ch += 'a' - 'A';
+		word[i] = ch;
+	}
+	word[len] = '\0';
+
+	/*
+	 * Now do a binary search using plain strcmp() comparison.
+	 */
+	low = keywords;
+	high = keywords + (num_keywords - 1);
+	while (low <= high)
+	{
+		const sqlol_ScanKeyword *middle;
+		int			difference;
+
+		middle = low + (high - low) / 2;
+		difference = strcmp(middle->name, word);
+		if (difference == 0)
+			return middle;
+		else if (difference < 0)
+			low = middle + 1;
+		else
+			high = middle - 1;
+	}
+
+	return NULL;
+}
diff --git a/contrib/sqlol/sqlol_keywords.h b/contrib/sqlol/sqlol_keywords.h
new file mode 100644
index 0000000000..bc4acf4541
--- /dev/null
+++ b/contrib/sqlol/sqlol_keywords.h
@@ -0,0 +1,38 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_keywords.h
+ *	  lexical token lookup for key words in PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_keywords.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SQLOL_KEYWORDS_H
+#define SQLOL_KEYWORDS_H
+
+/* Keyword categories --- should match lists in gram.y */
+#define UNRESERVED_KEYWORD		0
+#define COL_NAME_KEYWORD		1
+#define TYPE_FUNC_NAME_KEYWORD	2
+#define RESERVED_KEYWORD		3
+
+
+typedef struct sqlol_ScanKeyword
+{
+	const char *name;			/* in lower case */
+	int16		value;			/* grammar's token code */
+	int16		category;		/* see codes above */
+} sqlol_ScanKeyword;
+
+extern PGDLLIMPORT const sqlol_ScanKeyword sqlol_ScanKeywords[];
+extern PGDLLIMPORT const int sqlol_NumScanKeywords;
+
+extern const sqlol_ScanKeyword *sqlol_ScanKeywordLookup(const char *text,
+				  const sqlol_ScanKeyword *keywords,
+				  int num_keywords);
+
+#endif							/* SQLOL_KEYWORDS_H */
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
new file mode 100644
index 0000000000..2de3893ee4
--- /dev/null
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -0,0 +1,21 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_kwlist.h
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_kwlist.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* name, value, category, is-bare-label */
+PG_KEYWORD("a", A, UNRESERVED_KEYWORD)
+PG_KEYWORD("gimmeh", GIMMEH, UNRESERVED_KEYWORD)
+PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
+PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
+PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
+PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
new file mode 100644
index 0000000000..a7088b8390
--- /dev/null
+++ b/contrib/sqlol/sqlol_scan.l
@@ -0,0 +1,544 @@
+%top{
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scan.l
+ *	  lexical scanner for sqlol
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/sqlol/sqlol_scan.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "common/string.h"
+#include "sqlol_gramparse.h"
+#include "parser/scansup.h"
+#include "mb/pg_wchar.h"
+
+#include "sqlol_keywords.h"
+}
+
+%{
+
+/* LCOV_EXCL_START */
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+
+/*
+ * Set the type of YYSTYPE.
+ */
+#define YYSTYPE sqlol_YYSTYPE
+
+/*
+ * Set the type of yyextra.  All state variables used by the scanner should
+ * be in yyextra, *not* statically allocated.
+ */
+#define YY_EXTRA_TYPE sqlol_yy_extra_type *
+
+/*
+ * Each call to yylex must set yylloc to the location of the found token
+ * (expressed as a byte offset from the start of the input text).
+ * When we parse a token that requires multiple lexer rules to process,
+ * this should be done in the first such rule, else yylloc will point
+ * into the middle of the token.
+ */
+#define SET_YYLLOC()  (*(yylloc) = yytext - yyextra->scanbuf)
+
+/*
+ * Advance yylloc by the given number of bytes.
+ */
+#define ADVANCE_YYLLOC(delta)  ( *(yylloc) += (delta) )
+
+/*
+ * Sometimes, we do want yylloc to point into the middle of a token; this is
+ * useful for instance to throw an error about an escape sequence within a
+ * string literal.  But if we find no error there, we want to revert yylloc
+ * to the token start, so that that's the location reported to the parser.
+ * Use PUSH_YYLLOC/POP_YYLLOC to save/restore yylloc around such code.
+ * (Currently the implied "stack" is just one location, but someday we might
+ * need to nest these.)
+ */
+#define PUSH_YYLLOC()	(yyextra->save_yylloc = *(yylloc))
+#define POP_YYLLOC()	(*(yylloc) = yyextra->save_yylloc)
+
+#define startlit()	( yyextra->literallen = 0 )
+static void addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner);
+static void addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner);
+static char *litbufdup(sqlol_yyscan_t yyscanner);
+
+#define yyerror(msg)  sqlol_scanner_yyerror(msg, yyscanner)
+
+#define lexer_errposition()  sqlol_scanner_errposition(*(yylloc), yyscanner)
+
+/*
+ * Work around a bug in flex 2.5.35: it emits a couple of functions that
+ * it forgets to emit declarations for.  Since we use -Wmissing-prototypes,
+ * this would cause warnings.  Providing our own declarations should be
+ * harmless even when the bug gets fixed.
+ */
+extern int	sqlol_yyget_column(yyscan_t yyscanner);
+extern void sqlol_yyset_column(int column_no, yyscan_t yyscanner);
+
+%}
+
+%option reentrant
+%option bison-bridge
+%option bison-locations
+%option 8bit
+%option never-interactive
+%option nodefault
+%option noinput
+%option nounput
+%option noyywrap
+%option noyyalloc
+%option noyyrealloc
+%option noyyfree
+%option warn
+%option prefix="sqlol_yy"
+
+/*
+ * OK, here is a short description of lex/flex rules behavior.
+ * The longest pattern which matches an input string is always chosen.
+ * For equal-length patterns, the first occurring in the rules list is chosen.
+ * INITIAL is the starting state, to which all non-conditional rules apply.
+ * Exclusive states change parsing rules while the state is active.  When in
+ * an exclusive state, only those rules defined for that state apply.
+ *
+ * We use exclusive states for quoted strings, extended comments,
+ * and to eliminate parsing troubles for numeric strings.
+ * Exclusive states:
+ *  <xd> delimited identifiers (double-quoted identifiers)
+ *  <xq> standard quoted strings
+ *  <xqs> quote stop (detect continued strings)
+ *
+ * Remember to add an <<EOF>> case whenever you add a new exclusive state!
+ * The default one is probably not the right thing.
+ */
+
+%x xd
+%x xq
+%x xqs
+
+/*
+ * In order to make the world safe for Windows and Mac clients as well as
+ * Unix ones, we accept either \n or \r as a newline.  A DOS-style \r\n
+ * sequence will be seen as two successive newlines, but that doesn't cause
+ * any problems.  Comments that start with -- and extend to the next
+ * newline are treated as equivalent to a single whitespace character.
+ *
+ * NOTE a fine point: if there is no newline following --, we will absorb
+ * everything to the end of the input as a comment.  This is correct.  Older
+ * versions of Postgres failed to recognize -- as a comment if the input
+ * did not end with a newline.
+ *
+ * XXX perhaps \f (formfeed) should be treated as a newline as well?
+ *
+ * XXX if you change the set of whitespace characters, fix scanner_isspace()
+ * to agree.
+ */
+
+space			[ \t\n\r\f]
+horiz_space		[ \t\f]
+newline			[\n\r]
+non_newline		[^\n\r]
+
+comment			("--"{non_newline}*)
+
+whitespace		({space}+|{comment})
+
+/*
+ * SQL requires at least one newline in the whitespace separating
+ * string literals that are to be concatenated.  Silly, but who are we
+ * to argue?  Note that {whitespace_with_newline} should not have * after
+ * it, whereas {whitespace} should generally have a * after it...
+ */
+
+special_whitespace		({space}+|{comment}{newline})
+horiz_whitespace		({horiz_space}|{comment})
+whitespace_with_newline	({horiz_whitespace}*{newline}{special_whitespace}*)
+
+quote			'
+/* If we see {quote} then {quotecontinue}, the quoted string continues */
+quotecontinue	{whitespace_with_newline}{quote}
+
+/*
+ * {quotecontinuefail} is needed to avoid lexer backup when we fail to match
+ * {quotecontinue}.  It might seem that this could just be {whitespace}*,
+ * but if there's a dash after {whitespace_with_newline}, it must be consumed
+ * to see if there's another dash --- which would start a {comment} and thus
+ * allow continuation of the {quotecontinue} token.
+ */
+quotecontinuefail	{whitespace}*"-"?
+
+/* Extended quote
+ * xqdouble implements embedded quote, ''''
+ */
+xqstart			{quote}
+xqdouble		{quote}{quote}
+xqinside		[^']+
+
+/* Double quote
+ * Allows embedded spaces and other special characters into identifiers.
+ */
+dquote			\"
+xdstart			{dquote}
+xdstop			{dquote}
+xddouble		{dquote}{dquote}
+xdinside		[^"]+
+
+digit			[0-9]
+ident_start		[A-Za-z\200-\377_]
+ident_cont		[A-Za-z\200-\377_0-9\$]
+
+identifier		{ident_start}{ident_cont}*
+
+decimal			(({digit}+)|({digit}*\.{digit}+)|({digit}+\.{digit}*))
+
+other			.
+
+%%
+
+{whitespace}	{
+					/* ignore */
+				}
+
+
+{xqstart}		{
+					yyextra->saw_non_ascii = false;
+					SET_YYLLOC();
+					BEGIN(xq);
+					startlit();
+}
+<xq>{quote} {
+					/*
+					 * When we are scanning a quoted string and see an end
+					 * quote, we must look ahead for a possible continuation.
+					 * If we don't see one, we know the end quote was in fact
+					 * the end of the string.  To reduce the lexer table size,
+					 * we use a single "xqs" state to do the lookahead for all
+					 * types of strings.
+					 */
+					yyextra->state_before_str_stop = YYSTATE;
+					BEGIN(xqs);
+				}
+<xqs>{quotecontinue} {
+					/*
+					 * Found a quote continuation, so return to the in-quote
+					 * state and continue scanning the literal.  Nothing is
+					 * added to the literal's contents.
+					 */
+					BEGIN(yyextra->state_before_str_stop);
+				}
+<xqs>{quotecontinuefail} |
+<xqs>{other} |
+<xqs><<EOF>>	{
+					/*
+					 * Failed to see a quote continuation.  Throw back
+					 * everything after the end quote, and handle the string
+					 * according to the state we were in previously.
+					 */
+					yyless(0);
+					BEGIN(INITIAL);
+
+					switch (yyextra->state_before_str_stop)
+					{
+						case xq:
+							/*
+							 * Check that the data remains valid, if it might
+							 * have been made invalid by unescaping any chars.
+							 */
+							if (yyextra->saw_non_ascii)
+								pg_verifymbstr(yyextra->literalbuf,
+										yyextra->literallen,
+										false);
+							yylval->str = litbufdup(yyscanner);
+							return SCONST;
+						default:
+							yyerror("unhandled previous state in xqs");
+					}
+				}
+
+<xq>{xqdouble} {
+					addlitchar('\'', yyscanner);
+				}
+<xq>{xqinside}  {
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xq><<EOF>>		{ yyerror("unterminated quoted string"); }
+
+
+{xdstart}		{
+					SET_YYLLOC();
+					BEGIN(xd);
+					startlit();
+				}
+<xd>{xdstop}	{
+					char	   *ident;
+
+					BEGIN(INITIAL);
+					if (yyextra->literallen == 0)
+						yyerror("zero-length delimited identifier");
+					ident = litbufdup(yyscanner);
+					if (yyextra->literallen >= NAMEDATALEN)
+						truncate_identifier(ident, yyextra->literallen, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+<xd>{xddouble}	{
+					addlitchar('"', yyscanner);
+				}
+<xd>{xdinside}	{
+					addlit(yytext, yyleng, yyscanner);
+				}
+<xd><<EOF>>		{ yyerror("unterminated quoted identifier"); }
+
+{decimal}		{
+					SET_YYLLOC();
+					yylval->str = pstrdup(yytext);
+					return FCONST;
+				}
+
+{identifier}	{
+					const sqlol_ScanKeyword *keyword;
+					char	   *ident;
+
+					SET_YYLLOC();
+
+					/* Is it a keyword? */
+					keyword = sqlol_ScanKeywordLookup(yytext,
+													yyextra->keywords,
+													yyextra->num_keywords);
+					if (keyword != NULL)
+					{
+						yylval->keyword = keyword->name;
+						return keyword->value;
+					}
+
+					/*
+					 * No.  Convert the identifier to lower case, and truncate
+					 * if necessary.
+					 */
+					ident = downcase_truncate_identifier(yytext, yyleng, true);
+					yylval->str = ident;
+					return IDENT;
+				}
+
+{other}			{
+					SET_YYLLOC();
+					return yytext[0];
+				}
+
+<<EOF>>			{
+					SET_YYLLOC();
+					yyterminate();
+				}
+
+%%
+
+/* LCOV_EXCL_STOP */
+
+/*
+ * Arrange access to yyextra for subroutines of the main yylex() function.
+ * We expect each subroutine to have a yyscanner parameter.  Rather than
+ * use the yyget_xxx functions, which might or might not get inlined by the
+ * compiler, we cheat just a bit and cast yyscanner to the right type.
+ */
+#undef yyextra
+#define yyextra  (((struct yyguts_t *) yyscanner)->yyextra_r)
+
+/* Likewise for a couple of other things we need. */
+#undef yylloc
+#define yylloc	(((struct yyguts_t *) yyscanner)->yylloc_r)
+#undef yyleng
+#define yyleng	(((struct yyguts_t *) yyscanner)->yyleng_r)
+
+
+/*
+ * scanner_errposition
+ *		Report a lexer or grammar error cursor position, if possible.
+ *
+ * This is expected to be used within an ereport() call.  The return value
+ * is a dummy (always 0, in fact).
+ *
+ * Note that this can only be used for messages emitted during raw parsing
+ * (essentially, sqlol_scan.l, sqlol_parser.c, sqlol_and gram.y), since it
+ * requires the yyscanner struct to still be available.
+ */
+int
+sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner)
+{
+	int			pos;
+
+	if (location < 0)
+		return 0;				/* no-op if location is unknown */
+
+	/* Convert byte offset to character number */
+	pos = pg_mbstrlen_with_len(yyextra->scanbuf, location) + 1;
+	/* And pass it to the ereport mechanism */
+	return errposition(pos);
+}
+
+/*
+ * scanner_yyerror
+ *		Report a lexer or grammar error.
+ *
+ * Just ignore as we'll fallback to raw_parser().
+ */
+void
+sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner)
+{
+	return;
+}
+
+
+/*
+ * Called before any actual parsing is done
+ */
+sqlol_yyscan_t
+sqlol_scanner_init(const char *str,
+			 sqlol_yy_extra_type *yyext,
+			 const sqlol_ScanKeyword *keywords,
+			 int num_keywords)
+{
+	Size		slen = strlen(str);
+	yyscan_t	scanner;
+
+	if (yylex_init(&scanner) != 0)
+		elog(ERROR, "yylex_init() failed: %m");
+
+	sqlol_yyset_extra(yyext, scanner);
+
+	yyext->keywords = keywords;
+	yyext->num_keywords = num_keywords;
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	yyext->scanbuf = (char *) palloc(slen + 2);
+	yyext->scanbuflen = slen;
+	memcpy(yyext->scanbuf, str, slen);
+	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+
+	/* initialize literal buffer to a reasonable but expansible size */
+	yyext->literalalloc = 1024;
+	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
+	yyext->literallen = 0;
+
+	return scanner;
+}
+
+
+/*
+ * Called after parsing is done to clean up after scanner_init()
+ */
+void
+sqlol_scanner_finish(sqlol_yyscan_t yyscanner)
+{
+	/*
+	 * We don't bother to call yylex_destroy(), because all it would do is
+	 * pfree a small amount of control storage.  It's cheaper to leak the
+	 * storage until the parsing context is destroyed.  The amount of space
+	 * involved is usually negligible compared to the output parse tree
+	 * anyway.
+	 *
+	 * We do bother to pfree the scanbuf and literal buffer, but only if they
+	 * represent a nontrivial amount of space.  The 8K cutoff is arbitrary.
+	 */
+	if (yyextra->scanbuflen >= 8192)
+		pfree(yyextra->scanbuf);
+	if (yyextra->literalalloc >= 8192)
+		pfree(yyextra->literalbuf);
+}
+
+
+static void
+addlit(char *ytext, int yleng, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + yleng) >= yyextra->literalalloc)
+	{
+		do
+		{
+			yyextra->literalalloc *= 2;
+		} while ((yyextra->literallen + yleng) >= yyextra->literalalloc);
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	memcpy(yyextra->literalbuf + yyextra->literallen, ytext, yleng);
+	yyextra->literallen += yleng;
+}
+
+
+static void
+addlitchar(unsigned char ychar, sqlol_yyscan_t yyscanner)
+{
+	/* enlarge buffer if needed */
+	if ((yyextra->literallen + 1) >= yyextra->literalalloc)
+	{
+		yyextra->literalalloc *= 2;
+		yyextra->literalbuf = (char *) repalloc(yyextra->literalbuf,
+												yyextra->literalalloc);
+	}
+	/* append new data */
+	yyextra->literalbuf[yyextra->literallen] = ychar;
+	yyextra->literallen += 1;
+}
+
+
+/*
+ * Create a palloc'd copy of literalbuf, adding a trailing null.
+ */
+static char *
+litbufdup(sqlol_yyscan_t yyscanner)
+{
+	int			llen = yyextra->literallen;
+	char	   *new;
+
+	new = palloc(llen + 1);
+	memcpy(new, yyextra->literalbuf, llen);
+	new[llen] = '\0';
+	return new;
+}
+
+/*
+ * Interface functions to make flex use palloc() instead of malloc().
+ * It'd be better to make these static, but flex insists otherwise.
+ */
+
+void *
+sqlol_yyalloc(yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	return palloc(bytes);
+}
+
+void *
+sqlol_yyrealloc(void *ptr, yy_size_t bytes, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		return repalloc(ptr, bytes);
+	else
+		return palloc(bytes);
+}
+
+void
+sqlol_yyfree(void *ptr, sqlol_yyscan_t yyscanner)
+{
+	if (ptr)
+		pfree(ptr);
+}
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
new file mode 100644
index 0000000000..0a497e9d91
--- /dev/null
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -0,0 +1,118 @@
+/*-------------------------------------------------------------------------
+ *
+ * sqlol_scanner.h
+ *		API for the core scanner (flex machine)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * contrib/sqlol/sqlol_scanner.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SQLOL_SCANNER_H
+#define SQLOL_SCANNER_H
+
+#include "sqlol_keywords.h"
+
+/*
+ * The scanner returns extra data about scanned tokens in this union type.
+ * Note that this is a subset of the fields used in YYSTYPE of the bison
+ * parsers built atop the scanner.
+ */
+typedef union sqlol_YYSTYPE
+{
+	int			ival;			/* for integer literals */
+	char	   *str;			/* for identifiers and non-integer literals */
+	const char *keyword;		/* canonical spelling of keywords */
+} sqlol_YYSTYPE;
+
+/*
+ * We track token locations in terms of byte offsets from the start of the
+ * source string, not the column number/line number representation that
+ * bison uses by default.  Also, to minimize overhead we track only one
+ * location (usually the first token location) for each construct, not
+ * the beginning and ending locations as bison does by default.  It's
+ * therefore sufficient to make YYLTYPE an int.
+ */
+#define YYLTYPE  int
+
+/*
+ * Another important component of the scanner's API is the token code numbers.
+ * However, those are not defined in this file, because bison insists on
+ * defining them for itself.  The token codes used by the core scanner are
+ * the ASCII characters plus these:
+ *	%token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
+ *	%token <ival>	ICONST PARAM
+ *	%token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
+ *	%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+ * The above token definitions *must* be the first ones declared in any
+ * bison parser built atop this scanner, so that they will have consistent
+ * numbers assigned to them (specifically, IDENT = 258 and so on).
+ */
+
+/*
+ * The YY_EXTRA data that a flex scanner allows us to pass around.
+ * Private state needed by the core scanner goes here.  Note that the actual
+ * yy_extra struct may be larger and have this as its first component, thus
+ * allowing the calling parser to keep some fields of its own in YY_EXTRA.
+ */
+typedef struct sqlol_yy_extra_type
+{
+	/*
+	 * The string the scanner is physically scanning.  We keep this mainly so
+	 * that we can cheaply compute the offset of the current token (yytext).
+	 */
+	char	   *scanbuf;
+	Size		scanbuflen;
+
+	/*
+	 * The keyword list to use, and the associated grammar token codes.
+	 */
+	const sqlol_ScanKeyword *keywords;
+	int		num_keywords;
+
+	/*
+	 * literalbuf is used to accumulate literal values when multiple rules are
+	 * needed to parse a single literal.  Call startlit() to reset buffer to
+	 * empty, addlit() to add text.  NOTE: the string in literalbuf is NOT
+	 * necessarily null-terminated, but there always IS room to add a trailing
+	 * null at offset literallen.  We store a null only when we need it.
+	 */
+	char	   *literalbuf;		/* palloc'd expandable buffer */
+	int			literallen;		/* actual current string length */
+	int			literalalloc;	/* current allocated buffer size */
+
+	/*
+	 * Random assorted scanner state.
+	 */
+	int			state_before_str_stop;	/* start cond. before end quote */
+	YYLTYPE		save_yylloc;	/* one-element stack for PUSH_YYLLOC() */
+
+	/* state variables for literal-lexing warnings */
+	bool		saw_non_ascii;
+} sqlol_yy_extra_type;
+
+/*
+ * The type of yyscanner is opaque outside scan.l.
+ */
+typedef void *sqlol_yyscan_t;
+
+
+/* Constant data exported from parser/scan.l */
+extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
+
+/* Entry points in parser/scan.l */
+extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
+								  sqlol_yy_extra_type *yyext,
+								  const sqlol_ScanKeyword *keywords,
+								  int num_keywords);
+extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
+extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
+					   sqlol_yyscan_t yyscanner);
+extern int	sqlol_scanner_errposition(int location, sqlol_yyscan_t yyscanner);
+extern void sqlol_scanner_yyerror(const char *message, sqlol_yyscan_t yyscanner);
+
+#endif							/* SQLOL_SCANNER_H */
-- 
2.32.0

From 1577da8672747bf9bb3ef8cb22114b526b4419d1 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 01:33:42 +0800
Subject: [PATCH v5 3/4] Add a new MODE_SINGLE_QUERY to the core parser and use
 it in pg_parse_query.

If a third-party module provides a parser_hook, pg_parse_query() switches to
single-query parsing so multi-query commands using different grammar can work
properly.  If the third-party module supports the full set of SQL we support,
or want to prevent fallback on the core parser, it can ignore the
MODE_SINGLE_QUERY mode and parse the full query string.  In that case they must
return a List with more than one RawStmt or a single RawStmt with a 0 length to
stop the parsing phase, or raise an ERROR.

Otherwise, plugins should parse a single query only and always return a List
containing a single RawStmt with a properly set length (possibly 0 if it was a
single query without end of query delimiter).  If the command is valid but
doesn't contain any statements (e.g. a single semi-colon), a single RawStmt
with a NULL stmt field should be returned, containing the consumed query string
length so we can move to the next command in a single pass rather than 1 byte
at a time.

Also, third-party modules can choose to ignore some or all of parsing error if
they want to implement only subset of postgres suppoted syntax, or even a
totally different syntax, and fall-back on core grammar for unhandled case.  In
thase case, they should set the error flag to true.  The returned List will be
ignored and the same offset of the input string will be parsed using the core
parser.

Finally, note that third-party plugins that wants to fallback on other grammar
should first try to call a previous parser hook if any before setting the error
switch and returning.
---
 .../pg_stat_statements/pg_stat_statements.c   |   3 +-
 src/backend/commands/tablecmds.c              |   2 +-
 src/backend/executor/spi.c                    |   4 +-
 src/backend/parser/gram.y                     |  29 +++-
 src/backend/parser/parse_type.c               |   2 +-
 src/backend/parser/parser.c                   |  15 +-
 src/backend/parser/scan.l                     |  26 +++-
 src/backend/tcop/postgres.c                   | 138 ++++++++++++++++--
 src/include/parser/parser.h                   |   5 +-
 src/include/parser/scanner.h                  |   6 +-
 src/include/tcop/tcopprot.h                   |   3 +-
 src/pl/plpgsql/src/pl_gram.y                  |   2 +-
 src/pl/plpgsql/src/pl_scanner.c               |   2 +-
 13 files changed, 210 insertions(+), 27 deletions(-)

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 07fe0e7cda..6655ac12b9 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -2720,7 +2720,8 @@ fill_in_constant_lengths(JumbleState *jstate, const char *query,
 	yyscanner = scanner_init(query,
 							 &yyextra,
 							 &ScanKeywords,
-							 ScanKeywordTokens);
+							 ScanKeywordTokens,
+							 0);
 
 	/* we don't want to re-emit any escape string warnings */
 	yyextra.escape_string_warning = false;
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index dbee6ae199..770d3abe9a 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -12791,7 +12791,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 	 * parse_analyze() or the rewriter, but instead we need to pass them
 	 * through parse_utilcmd.c to make them ready for execution.
 	 */
-	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT);
+	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT, 0);
 	querytree_list = NIL;
 	foreach(list_item, raw_parsetree_list)
 	{
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index a5aec7ba7d..dc6c1dea1d 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -2126,7 +2126,7 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Do parse analysis and rule rewrite for each raw parsetree, storing the
@@ -2234,7 +2234,7 @@ _SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan)
 	/*
 	 * Parse the request string into a list of raw parse trees.
 	 */
-	raw_parsetree_list = raw_parser(src, plan->parse_mode);
+	raw_parsetree_list = raw_parser(src, plan->parse_mode, 0);
 
 	/*
 	 * Construct plancache entries, but don't do parse analysis yet.
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index e3068a374e..843b27ff39 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -625,7 +625,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token <str>	IDENT UIDENT FCONST SCONST USCONST BCONST XCONST Op
 %token <ival>	ICONST PARAM
 %token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
-%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS
+%token			LESS_EQUALS GREATER_EQUALS NOT_EQUALS END_OF_FILE
 
 /*
  * If you want to make any keyword changes, update the keyword table in
@@ -752,6 +752,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %token		MODE_PLPGSQL_ASSIGN1
 %token		MODE_PLPGSQL_ASSIGN2
 %token		MODE_PLPGSQL_ASSIGN3
+%token		MODE_SINGLE_QUERY
 
 
 /* Precedence: lowest to highest */
@@ -857,6 +858,32 @@ parse_toplevel:
 				pg_yyget_extra(yyscanner)->parsetree =
 					list_make1(makeRawStmt((Node *) n, 0));
 			}
+			| MODE_SINGLE_QUERY toplevel_stmt ';'
+			{
+				RawStmt *raw = makeRawStmt($2, 0);
+				updateRawStmtEnd(raw, @3 + 1);
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string and move to the next command.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(raw);
+				YYACCEPT;
+			}
+			/*
+			 * We need to explicitly look for EOF to parse non-semicolon
+			 * terminated statements in single query mode, as we could
+			 * otherwise successfully parse the beginning of an otherwise
+			 * invalid query.
+			 */
+			| MODE_SINGLE_QUERY toplevel_stmt END_OF_FILE
+			{
+				/* NOTE: we can return a raw statement containing a NULL stmt.
+				 * This is done to allow pg_parse_query to ignore that part of
+				 * the input string.
+				 */
+				pg_yyget_extra(yyscanner)->parsetree = list_make1(makeRawStmt($2, 0));
+				YYACCEPT;
+			}
 		;
 
 /*
diff --git a/src/backend/parser/parse_type.c b/src/backend/parser/parse_type.c
index 31b07ad5ae..576726cb5b 100644
--- a/src/backend/parser/parse_type.c
+++ b/src/backend/parser/parse_type.c
@@ -750,7 +750,7 @@ typeStringToTypeName(const char *str)
 	ptserrcontext.previous = error_context_stack;
 	error_context_stack = &ptserrcontext;
 
-	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME);
+	raw_parsetree_list = raw_parser(str, RAW_PARSE_TYPE_NAME, 0);
 
 	error_context_stack = ptserrcontext.previous;
 
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index 875de7ba28..23fd49e74c 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -37,17 +37,25 @@ static char *str_udeescape(const char *str, char escape,
  *
  * Returns a list of raw (un-analyzed) parse trees.  The contents of the
  * list have the form required by the specified RawParseMode.
+ *
+ * For all mode different from MODE_SINGLE_QUERY, caller should provide a 0
+ * offset as the whole input string should be parsed.  Otherwise, caller should
+ * provide the wanted offset in the input string, or -1 if no offset is
+ * required.
  */
 List *
-raw_parser(const char *str, RawParseMode mode)
+raw_parser(const char *str, RawParseMode mode, int offset)
 {
 	core_yyscan_t yyscanner;
 	base_yy_extra_type yyextra;
 	int			yyresult;
 
+	Assert((mode != RAW_PARSE_SINGLE_QUERY && offset == 0) ||
+			(mode == RAW_PARSE_SINGLE_QUERY && offset != 0));
+
 	/* initialize the flex scanner */
 	yyscanner = scanner_init(str, &yyextra.core_yy_extra,
-							 &ScanKeywords, ScanKeywordTokens);
+							 &ScanKeywords, ScanKeywordTokens, offset);
 
 	/* base_yylex() only needs us to initialize the lookahead token, if any */
 	if (mode == RAW_PARSE_DEFAULT)
@@ -61,7 +69,8 @@ raw_parser(const char *str, RawParseMode mode)
 			MODE_PLPGSQL_EXPR,	/* RAW_PARSE_PLPGSQL_EXPR */
 			MODE_PLPGSQL_ASSIGN1,	/* RAW_PARSE_PLPGSQL_ASSIGN1 */
 			MODE_PLPGSQL_ASSIGN2,	/* RAW_PARSE_PLPGSQL_ASSIGN2 */
-			MODE_PLPGSQL_ASSIGN3	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_PLPGSQL_ASSIGN3,	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
+			MODE_SINGLE_QUERY		/* RAW_PARSE_SINGLE_QUERY */
 		};
 
 		yyextra.have_lookahead = true;
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
index 6e6824faeb..156c0df7d7 100644
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -1042,7 +1042,10 @@ other			.
 
 <<EOF>>			{
 					SET_YYLLOC();
-					yyterminate();
+					if (yyextra->return_eof)
+						return END_OF_FILE;
+					else
+						yyterminate();
 				}
 
 %%
@@ -1190,8 +1193,10 @@ core_yyscan_t
 scanner_init(const char *str,
 			 core_yy_extra_type *yyext,
 			 const ScanKeywordList *keywordlist,
-			 const uint16 *keyword_tokens)
+			 const uint16 *keyword_tokens,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -1214,13 +1219,28 @@ scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Note that pg_parse_query will set a -1 offset rather than 0 for the
+	 * first query of a possibly multi-query string if it wants us to return an
+	 * EOF token.
+	 */
+	yyext->return_eof = (offset != 0);
+
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	if (offset > 0)
+		state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 66ee58a4b1..d94d2b3c10 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -602,17 +602,137 @@ ProcessClientWriteInterrupt(bool blocked)
 List *
 pg_parse_query(const char *query_string)
 {
-	List	   *raw_parsetree_list = NIL;
+	List		   *result = NIL;
+	int				stmt_len, offset;
 
 	TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);
 
 	if (log_parser_stats)
 		ResetUsage();
 
-	if (parser_hook)
-		raw_parsetree_list = (*parser_hook) (query_string, RAW_PARSE_DEFAULT);
-	else
-		raw_parsetree_list = raw_parser(query_string, RAW_PARSE_DEFAULT);
+	stmt_len = 0; /* lazily computed when needed */
+	offset = 0;
+
+	while(true)
+	{
+		List *raw_parsetree_list;
+		RawStmt *raw;
+		bool	error = false;
+
+		/*----------------
+		 * Start parsing the input string.  If a third-party module provided a
+		 * parser_hook, we switch to single-query parsing so multi-query
+		 * commands using different grammar can work properly.
+		 * If the third-party modules support the full set of SQL we support,
+		 * or want to prevent fallback on the core parser, it can ignore the
+		 * RAW_PARSE_SINGLE_QUERY flag and parse the full query string.
+		 * In that case they must return a List with more than one RawStmt or a
+		 * single RawStmt with a 0 length to stop the parsing phase, or raise
+		 * an ERROR.
+		 *
+		 * Otherwise, plugins should parse a single query only and always
+		 * return a List containing a single RawStmt with a properly set length
+		 * (possibly 0 if it was a single query without end of query
+		 * delimiter).  If the command is valid but doesn't contain any
+		 * statements (e.g. a single semi-colon), a single RawStmt with a NULL
+		 * stmt field should be returned, containing the consumed query string
+		 * length so we can move to the next command in a single pass rather
+		 * than 1 byte at a time.
+		 *
+		 * Also, third-party modules can choose to ignore some or all of
+		 * parsing error if they want to implement only subset of postgres
+		 * suppoted syntax, or even a totally different syntax, and fall-back
+		 * on core grammar for unhandled case.  In thase case, they should set
+		 * the error flag to true.  The returned List will be ignored and the
+		 * same offset of the input string will be parsed using the core
+		 * parser.
+		 *
+		 * Finally, note that third-party modules that wants to fallback on
+		 * other grammar should first try to call a previous parser hook if any
+		 * before setting the error switch and returning .
+		 */
+		if (parser_hook)
+			raw_parsetree_list = (*parser_hook) (query_string,
+												 RAW_PARSE_SINGLE_QUERY,
+												 offset,
+												 &error);
+
+		/*
+		 * If a third-party module couldn't parse a single query or if no
+		 * third-party module is configured, fallback on core parser.
+		 */
+		if (error || !parser_hook)
+		{
+			/* Send a -1 offset to raw_parser to specify that it should
+			 * explicitly detect EOF during parsing.  scanner_init() will treat
+			 * it the same as a 0 offset.
+			 */
+			raw_parsetree_list = raw_parser(query_string,
+					error ? RAW_PARSE_SINGLE_QUERY : RAW_PARSE_DEFAULT,
+					(error && offset == 0) ? -1 : offset);
+		}
+
+		/*
+		 * If there are no third-party plugin, or none of the parsers found a
+		 * valid query, or if a third party module consumed the whole
+		 * query string we're done.
+		 */
+		if (!parser_hook || raw_parsetree_list == NIL ||
+			list_length(raw_parsetree_list) > 1)
+		{
+			/*
+			 * Warn third-party plugins if they mix "single query" and "whole
+			 * input string" strategy rather than silently accepting it and
+			 * maybe allow fallback on core grammar even if they want to avoid
+			 * that.  This way plugin authors can be warned early of the issue.
+			 */
+			if (result != NIL)
+			{
+				Assert(parser_hook != NULL);
+				elog(ERROR, "parser_hook should parse a single statement at "
+						"a time or consume the whole input string at once");
+			}
+			result = raw_parsetree_list;
+			break;
+		}
+
+		if (stmt_len == 0)
+			stmt_len = strlen(query_string);
+
+		raw = linitial_node(RawStmt, raw_parsetree_list);
+
+		/*
+		 * In single-query mode, the parser will return statement location info
+		 * relative to the beginning of complete original string, not the part
+		 * we just parsed, so adjust the location info.
+		 */
+		if (offset > 0 && raw->stmt_len > 0)
+		{
+			Assert(raw->stmt_len > offset);
+			raw->stmt_location = offset;
+			raw->stmt_len -= offset;
+		}
+
+		/* Ignore the statement if it didn't contain any command. */
+		if (raw->stmt)
+			result = lappend(result, raw);
+
+		if (raw->stmt_len == 0)
+		{
+			/* The statement was the whole string, we're done. */
+			break;
+		}
+		else if (raw->stmt_len + offset >= stmt_len)
+		{
+			/* We consumed all of the input string, we're done. */
+			break;
+		}
+		else
+		{
+			/* Advance the offset to the next command. */
+			offset += raw->stmt_len;
+		}
+	}
 
 	if (log_parser_stats)
 		ShowUsage("PARSER STATISTICS");
@@ -620,13 +740,13 @@ pg_parse_query(const char *query_string)
 #ifdef COPY_PARSE_PLAN_TREES
 	/* Optional debugging check: pass raw parsetrees through copyObject() */
 	{
-		List	   *new_list = copyObject(raw_parsetree_list);
+		List	   *new_list = copyObject(result);
 
 		/* This checks both copyObject() and the equal() routines... */
-		if (!equal(new_list, raw_parsetree_list))
+		if (!equal(new_list, result))
 			elog(WARNING, "copyObject() failed to produce an equal raw parse tree");
 		else
-			raw_parsetree_list = new_list;
+			result = new_list;
 	}
 #endif
 
@@ -638,7 +758,7 @@ pg_parse_query(const char *query_string)
 
 	TRACE_POSTGRESQL_QUERY_PARSE_DONE(query_string);
 
-	return raw_parsetree_list;
+	return result;
 }
 
 /*
diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h
index 853b0f1606..5694ae791a 100644
--- a/src/include/parser/parser.h
+++ b/src/include/parser/parser.h
@@ -41,7 +41,8 @@ typedef enum
 	RAW_PARSE_PLPGSQL_EXPR,
 	RAW_PARSE_PLPGSQL_ASSIGN1,
 	RAW_PARSE_PLPGSQL_ASSIGN2,
-	RAW_PARSE_PLPGSQL_ASSIGN3
+	RAW_PARSE_PLPGSQL_ASSIGN3,
+	RAW_PARSE_SINGLE_QUERY
 } RawParseMode;
 
 /* Values for the backslash_quote GUC */
@@ -59,7 +60,7 @@ extern PGDLLIMPORT bool standard_conforming_strings;
 
 
 /* Primary entry point for the raw parsing functions */
-extern List *raw_parser(const char *str, RawParseMode mode);
+extern List *raw_parser(const char *str, RawParseMode mode, int offset);
 
 /* Utility functions exported by gram.y (perhaps these should be elsewhere) */
 extern List *SystemFuncName(char *name);
diff --git a/src/include/parser/scanner.h b/src/include/parser/scanner.h
index 0d8182faa0..a2e97be5d5 100644
--- a/src/include/parser/scanner.h
+++ b/src/include/parser/scanner.h
@@ -113,6 +113,9 @@ typedef struct core_yy_extra_type
 	/* state variables for literal-lexing warnings */
 	bool		warn_on_first_escape;
 	bool		saw_non_ascii;
+
+	/* state variable for returning an EOF token in single query mode */
+	bool		return_eof;
 } core_yy_extra_type;
 
 /*
@@ -136,7 +139,8 @@ extern PGDLLIMPORT const uint16 ScanKeywordTokens[];
 extern core_yyscan_t scanner_init(const char *str,
 								  core_yy_extra_type *yyext,
 								  const ScanKeywordList *keywordlist,
-								  const uint16 *keyword_tokens);
+								  const uint16 *keyword_tokens,
+								  int offset);
 extern void scanner_finish(core_yyscan_t yyscanner);
 extern int	core_yylex(core_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   core_yyscan_t yyscanner);
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 131dc2b22e..27201dde1d 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -45,7 +45,8 @@ typedef enum
 extern PGDLLIMPORT int log_statement;
 
 /* Hook for plugins to get control in pg_parse_query() */
-typedef List *(*parser_hook_type) (const char *str, RawParseMode mode);
+typedef List *(*parser_hook_type) (const char *str, RawParseMode mode,
+								   int offset, bool *error);
 extern PGDLLIMPORT parser_hook_type parser_hook;
 
 extern List *pg_parse_query(const char *query_string);
diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y
index 0f6a5b30b1..5c4f4c08bc 100644
--- a/src/pl/plpgsql/src/pl_gram.y
+++ b/src/pl/plpgsql/src/pl_gram.y
@@ -3656,7 +3656,7 @@ check_sql_expr(const char *stmt, RawParseMode parseMode, int location)
 	error_context_stack = &syntax_errcontext;
 
 	oldCxt = MemoryContextSwitchTo(plpgsql_compile_tmp_cxt);
-	(void) raw_parser(stmt, parseMode);
+	(void) raw_parser(stmt, parseMode, 0);
 	MemoryContextSwitchTo(oldCxt);
 
 	/* Restore former ereport callback */
diff --git a/src/pl/plpgsql/src/pl_scanner.c b/src/pl/plpgsql/src/pl_scanner.c
index e4c7a91ab5..a2886c42ec 100644
--- a/src/pl/plpgsql/src/pl_scanner.c
+++ b/src/pl/plpgsql/src/pl_scanner.c
@@ -587,7 +587,7 @@ plpgsql_scanner_init(const char *str)
 {
 	/* Start up the core scanner */
 	yyscanner = scanner_init(str, &core_yy,
-							 &ReservedPLKeywords, ReservedPLKeywordTokens);
+							 &ReservedPLKeywords, ReservedPLKeywordTokens, 0);
 
 	/*
 	 * scanorig points to the original string, which unlike the scanner's
-- 
2.32.0

From 8a17a647b4249400754bc026a221735ef9f7c523 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Thu, 22 Apr 2021 02:15:54 +0800
Subject: [PATCH v5 4/4] Teach sqlol to use the new MODE_SINGLE_QUERY parser
 mode.

This way multi-statements commands using both core parser and sqlol parser can
be supported.

Also add a LOLCODE version of CREATE VIEW viewname AS to easily test
multi-statements commands.
---
 contrib/sqlol/Makefile              |  2 +
 contrib/sqlol/expected/01_sqlol.out | 77 +++++++++++++++++++++++++++++
 contrib/sqlol/repro.sql             | 18 +++++++
 contrib/sqlol/sql/01_sqlol.sql      | 44 +++++++++++++++++
 contrib/sqlol/sqlol.c               | 24 +++++----
 contrib/sqlol/sqlol_gram.y          | 63 +++++++++++------------
 contrib/sqlol/sqlol_kwlist.h        |  1 +
 contrib/sqlol/sqlol_scan.l          | 13 ++++-
 contrib/sqlol/sqlol_scanner.h       |  3 +-
 9 files changed, 199 insertions(+), 46 deletions(-)
 create mode 100644 contrib/sqlol/expected/01_sqlol.out
 create mode 100644 contrib/sqlol/repro.sql
 create mode 100644 contrib/sqlol/sql/01_sqlol.sql

diff --git a/contrib/sqlol/Makefile b/contrib/sqlol/Makefile
index 3850ac3fce..eaf94801c2 100644
--- a/contrib/sqlol/Makefile
+++ b/contrib/sqlol/Makefile
@@ -6,6 +6,8 @@ OBJS = \
 	sqlol.o sqlol_gram.o sqlol_scan.o sqlol_keywords.o
 PGFILEDESC = "sqlol - Toy alternative grammar based on LOLCODE"
 
+REGRESS = 01_sqlol
+
 sqlol_gram.h: sqlol_gram.c
 	touch $@
 
diff --git a/contrib/sqlol/expected/01_sqlol.out b/contrib/sqlol/expected/01_sqlol.out
new file mode 100644
index 0000000000..9c51dd62c2
--- /dev/null
+++ b/contrib/sqlol/expected/01_sqlol.out
@@ -0,0 +1,77 @@
+LOAD 'sqlol';
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+ id | val 
+----+-----
+(0 rows)
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+ id | id 
+----+----
+(0 rows)
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+ ?column? 
+----------
+        3
+(1 row)
+
+-- test empty statement ignoring
+\;\;select 1 \g
+ ?column? 
+----------
+        1
+(1 row)
+
+-- check the created views
+SELECT relname, relkind
+FROM pg_class c
+JOIN pg_namespace n ON c.relnamespace = n.oid
+WHERE nspname = 'public'
+ORDER BY relname COLLATE "C";
+ relname | relkind 
+---------+---------
+ t1      | r
+ v0      | v
+ v1      | v
+ v2      | v
+ v3      | v
+ v4      | v
+ v5      | v
+(7 rows)
+
+--
+-- Error position
+--
+SELECT 1\;err;
+ERROR:  syntax error at or near "err"
+LINE 1: SELECT 1;err;
+                 ^
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+ERROR:  syntax error at or near "HAI"
+LINE 1: SELECT 1;HAI 1.2 I HAS A t1 GIMME id KTHXBYE
+                 ^
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+ERROR:  improper qualified name (too many dotted names): some.thing.public.t1
+LINE 1: SELECT 1;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHX...
+                                 ^
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
+ERROR:  relation "notatable" does not exist
+LINE 1: SELECT 1;SELECT * FROM notatable;
+                               ^
diff --git a/contrib/sqlol/repro.sql b/contrib/sqlol/repro.sql
new file mode 100644
index 0000000000..0ebcb53160
--- /dev/null
+++ b/contrib/sqlol/repro.sql
@@ -0,0 +1,18 @@
+DROP TABLE IF EXISTS t1 CASCADE;
+
+LOAD 'sqlol';
+
+\;\; SELECT 1\;
+
+CREATE TABLE t1 (id integer, val text);
+
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+SELECT 1\;SELECT 2\;SELECT 3 \g
+\d
diff --git a/contrib/sqlol/sql/01_sqlol.sql b/contrib/sqlol/sql/01_sqlol.sql
new file mode 100644
index 0000000000..e89a3dd9a0
--- /dev/null
+++ b/contrib/sqlol/sql/01_sqlol.sql
@@ -0,0 +1,44 @@
+LOAD 'sqlol';
+
+-- create a base table, falling back on core grammar
+CREATE TABLE t1 (id integer, val text);
+
+-- test a SQLOL statement
+HAI 1.2 I HAS A t1 GIMMEH id, "val" KTHXBYE\g
+
+-- create a view in SQLOL
+HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v0 KTHXBYE\g
+
+-- combine standard SQL with a trailing SQLOL statement in multi-statements command
+CREATE VIEW v1 AS SELECT * FROM t1\; CREATE VIEW v2 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- interleave standard SQL and SQLOL commands in multi-statements command
+CREATE VIEW v3 AS SELECT * FROM t1\; HAI 1.2 MAEK I HAS A t1 GIMMEH id, "val" A v4 KTHXBYE CREATE VIEW v5 AS SELECT * FROM t1\;HAI 1.2 I HAS A t1 GIMMEH "id", id KTHXBYE\g
+
+-- test MODE_SINGLE_QUERY with no trailing semicolon
+SELECT 1\;SELECT 2\;SELECT 3 \g
+
+-- test empty statement ignoring
+\;\;select 1 \g
+
+-- check the created views
+SELECT relname, relkind
+FROM pg_class c
+JOIN pg_namespace n ON c.relnamespace = n.oid
+WHERE nspname = 'public'
+ORDER BY relname COLLATE "C";
+
+--
+-- Error position
+--
+SELECT 1\;err;
+
+-- sqlol won't trigger an error on incorrect GIMME keyword, so core parser will
+-- complain about HAI
+SELECT 1\;HAI 1.2 I HAS A t1 GIMME id KTHXBYE\g
+
+-- sqlol will trigger the error about too many qualifiers on t1
+SELECT 1\;HAI 1.2 I HAS A some.thing.public.t1 GIMMEH id KTHXBYE\g
+
+-- position reported outside of the parser/scanner should be correct too
+SELECT 1\;SELECT * FROM notatable;
diff --git a/contrib/sqlol/sqlol.c b/contrib/sqlol/sqlol.c
index b986966181..7d4e1b631f 100644
--- a/contrib/sqlol/sqlol.c
+++ b/contrib/sqlol/sqlol.c
@@ -26,7 +26,8 @@ static parser_hook_type prev_parser_hook = NULL;
 void		_PG_init(void);
 void		_PG_fini(void);
 
-static List *sqlol_parser_hook(const char *str, RawParseMode mode);
+static List *sqlol_parser_hook(const char *str, RawParseMode mode, int offset,
+							   bool *error);
 
 
 /*
@@ -54,23 +55,25 @@ _PG_fini(void)
  * sqlol_parser_hook: parse our grammar
  */
 static List *
-sqlol_parser_hook(const char *str, RawParseMode mode)
+sqlol_parser_hook(const char *str, RawParseMode mode, int offset, bool *error)
 {
 	sqlol_yyscan_t yyscanner;
 	sqlol_base_yy_extra_type yyextra;
 	int			yyresult;
 
-	if (mode != RAW_PARSE_DEFAULT)
+	if (mode != RAW_PARSE_DEFAULT && mode != RAW_PARSE_SINGLE_QUERY)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	/* initialize the flex scanner */
 	yyscanner = sqlol_scanner_init(str, &yyextra.sqlol_yy_extra,
-							 sqlol_ScanKeywords, sqlol_NumScanKeywords);
+							 sqlol_ScanKeywords, sqlol_NumScanKeywords,
+							 offset);
 
 	/* initialize the bison parser */
 	sqlol_parser_init(&yyextra);
@@ -88,9 +91,10 @@ sqlol_parser_hook(const char *str, RawParseMode mode)
 	if (yyresult)
 	{
 		if (prev_parser_hook)
-			return (*prev_parser_hook) (str, mode);
-		else
-			return raw_parser(str, mode);
+			return (*prev_parser_hook) (str, mode, offset, error);
+
+		*error = true;
+		return NIL;
 	}
 
 	return yyextra.parsetree;
diff --git a/contrib/sqlol/sqlol_gram.y b/contrib/sqlol/sqlol_gram.y
index 3214865a53..94e20c2018 100644
--- a/contrib/sqlol/sqlol_gram.y
+++ b/contrib/sqlol/sqlol_gram.y
@@ -20,6 +20,7 @@
 
 #include "catalog/namespace.h"
 #include "nodes/makefuncs.h"
+#include "catalog/pg_class_d.h"
 
 #include "sqlol_gramparse.h"
 
@@ -105,10 +106,10 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
 	ResTarget			*target;
 }
 
-%type <node>	stmt toplevel_stmt GimmehStmt simple_gimmeh columnref
+%type <node>	stmt toplevel_stmt GimmehStmt MaekStmt simple_gimmeh columnref
 				indirection_el
 
-%type <list>	parse_toplevel stmtmulti gimmeh_list indirection
+%type <list>	parse_toplevel rawstmt gimmeh_list indirection
 
 %type <range>	qualified_name
 
@@ -133,22 +134,19 @@ static List *check_indirection(List *indirection, sqlol_yyscan_t yyscanner);
  */
 
 /* ordinary key words in alphabetical order */
-%token <keyword> A GIMMEH HAI HAS I KTHXBYE
-
+%token <keyword> A GIMMEH HAI HAS I KTHXBYE MAEK
 
 %%
 
 /*
  *	The target production for the whole parse.
- *
- * Ordinarily we parse a list of statements, but if we see one of the
- * special MODE_XXX symbols as first token, we parse something else.
- * The options here correspond to enum RawParseMode, which see for details.
  */
 parse_toplevel:
-			stmtmulti
+			rawstmt
 			{
 				pg_yyget_extra(yyscanner)->parsetree = $1;
+
+				YYACCEPT;
 			}
 		;
 
@@ -162,24 +160,11 @@ parse_toplevel:
  * we'd get -1 for the location in such cases.
  * We also take care to discard empty statements entirely.
  */
-stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
-				{
-					if ($1 != NIL)
-					{
-						/* update length of previous stmt */
-						updateRawStmtEnd(llast_node(RawStmt, $1), @2);
-					}
-					if ($3 != NULL)
-						$$ = lappend($1, makeRawStmt($3, @2 + 1));
-					else
-						$$ = $1;
-				}
-			| toplevel_stmt
+rawstmt:	toplevel_stmt KTHXBYE
 				{
-					if ($1 != NULL)
-						$$ = list_make1(makeRawStmt($1, 0));
-					else
-						$$ = NIL;
+					RawStmt *raw = makeRawStmt($1, 0);
+					updateRawStmtEnd(raw, @2 + 7);
+					$$ = list_make1(raw);
 				}
 		;
 
@@ -188,13 +173,12 @@ stmtmulti:	stmtmulti KTHXBYE toplevel_stmt
  * those words have different meanings in function bodys.
  */
 toplevel_stmt:
-			stmt
+			HAI FCONST stmt { $$ = $3; }
 		;
 
 stmt:
 			GimmehStmt
-			| /*EMPTY*/
-				{ $$ = NULL; }
+			| MaekStmt
 		;
 
 /*****************************************************************************
@@ -208,12 +192,11 @@ GimmehStmt:
 		;
 
 simple_gimmeh:
-			HAI FCONST I HAS A qualified_name
-			GIMMEH gimmeh_list
+			I HAS A qualified_name GIMMEH gimmeh_list
 				{
 					SelectStmt *n = makeNode(SelectStmt);
-					n->targetList = $8;
-					n->fromClause = list_make1($6);
+					n->targetList = $6;
+					n->fromClause = list_make1($4);
 					$$ = (Node *)n;
 				}
 		;
@@ -232,6 +215,20 @@ gimmeh_el:
 				$$->location = @1;
 			}
 
+MaekStmt:
+		MAEK GimmehStmt A qualified_name
+			{
+				ViewStmt *n = makeNode(ViewStmt);
+				n->view = $4;
+				n->view->relpersistence = RELPERSISTENCE_PERMANENT;
+				n->aliases = NIL;
+				n->query = $2;
+				n->replace = false;
+				n->options = NIL;
+				n->withCheckOption = false;
+				$$ = (Node *) n;
+			}
+
 qualified_name:
 			ColId
 				{
diff --git a/contrib/sqlol/sqlol_kwlist.h b/contrib/sqlol/sqlol_kwlist.h
index 2de3893ee4..8b50d88df9 100644
--- a/contrib/sqlol/sqlol_kwlist.h
+++ b/contrib/sqlol/sqlol_kwlist.h
@@ -19,3 +19,4 @@ PG_KEYWORD("hai", HAI, RESERVED_KEYWORD)
 PG_KEYWORD("has", HAS, UNRESERVED_KEYWORD)
 PG_KEYWORD("i", I, UNRESERVED_KEYWORD)
 PG_KEYWORD("kthxbye", KTHXBYE, UNRESERVED_KEYWORD)
+PG_KEYWORD("maek", MAEK, UNRESERVED_KEYWORD)
diff --git a/contrib/sqlol/sqlol_scan.l b/contrib/sqlol/sqlol_scan.l
index a7088b8390..e6d4d53446 100644
--- a/contrib/sqlol/sqlol_scan.l
+++ b/contrib/sqlol/sqlol_scan.l
@@ -412,8 +412,10 @@ sqlol_yyscan_t
 sqlol_scanner_init(const char *str,
 			 sqlol_yy_extra_type *yyext,
 			 const sqlol_ScanKeyword *keywords,
-			 int num_keywords)
+			 int num_keywords,
+			 int offset)
 {
+	YY_BUFFER_STATE state;
 	Size		slen = strlen(str);
 	yyscan_t	scanner;
 
@@ -432,13 +434,20 @@ sqlol_scanner_init(const char *str,
 	yyext->scanbuflen = slen;
 	memcpy(yyext->scanbuf, str, slen);
 	yyext->scanbuf[slen] = yyext->scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
-	yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
+	state = yy_scan_buffer(yyext->scanbuf, slen + 2, scanner);
 
 	/* initialize literal buffer to a reasonable but expansible size */
 	yyext->literalalloc = 1024;
 	yyext->literalbuf = (char *) palloc(yyext->literalalloc);
 	yyext->literallen = 0;
 
+	/*
+	 * Adjust the offset in the input string.  This is required in single-query
+	 * mode, as we need to register the same token locations as we would have
+	 * in normal mode with multi-statement query string.
+	 */
+	state->yy_buf_pos += offset;
+
 	return scanner;
 }
 
diff --git a/contrib/sqlol/sqlol_scanner.h b/contrib/sqlol/sqlol_scanner.h
index 0a497e9d91..57f95867ee 100644
--- a/contrib/sqlol/sqlol_scanner.h
+++ b/contrib/sqlol/sqlol_scanner.h
@@ -108,7 +108,8 @@ extern PGDLLIMPORT const uint16 sqlol_ScanKeywordTokens[];
 extern sqlol_yyscan_t sqlol_scanner_init(const char *str,
 								  sqlol_yy_extra_type *yyext,
 								  const sqlol_ScanKeyword *keywords,
-								  int num_keywords);
+								  int num_keywords,
+								  int offset);
 extern void sqlol_scanner_finish(sqlol_yyscan_t yyscanner);
 extern int	sqlol_yylex(sqlol_YYSTYPE *lvalp, YYLTYPE *llocp,
 					   sqlol_yyscan_t yyscanner);
-- 
2.32.0