From 87fb63d70f5e08f853a2b8aa94e03c0d665f5000 Mon Sep 17 00:00:00 2001
From: David Fetter <david.fetter@aiven.io>
Date: Thu, 7 Oct 2021 15:59:06 -0700
Subject: [PATCH v9 1/2] Infrastructure for tab completion in the SELECT list

---
 src/bin/psql/tab-complete.c | 65 ++++++++++++++++++++++++++++++-------
 1 file changed, 54 insertions(+), 11 deletions(-)

diff --git src/bin/psql/tab-complete.c src/bin/psql/tab-complete.c
index ecae9df8ed..5db143523b 100644
--- src/bin/psql/tab-complete.c
+++ src/bin/psql/tab-complete.c
@@ -1017,6 +1017,45 @@ static const VersionedQuery Query_for_list_of_subscriptions[] = {
 	{0, NULL}
 };
 
+static const SchemaQuery Query_for_list_of_selectable_functions[] = {
+	{
+		/* min_server_version */
+		70400,
+		/* catname */
+		"pg_catalog.pg_proc p",
+		/* Disallow functions which take or return pseudotypes which are other than all* or *record */
+		"NOT((ARRAY[p.prorettype] || coalesce(p.proallargtypes, p.proargtypes)) "
+		"    && ARRAY(SELECT oid FROM pg_catalog.pg_type WHERE typtype='p' AND typname !~ '(^all|record$)'))"
+		/* Disallow stored procedures XXX this may change later. */
+		" AND p.prokind <> 'p'"
+		/* viscondition */
+		"pg_catalog.pg_function_is_visible(p.oid)",
+		/* namespace */
+		"p.pronamespace",
+		/* result */
+		"pg_catalog.quote_ident(p.proname)||'('",
+		/* qualresult */
+		NULL
+	},
+	{0, NULL}
+};
+
+/*
+ * This addon is used to find (unqualified) column names to include
+ * alongside the function names from the query above.
+ */
+static const VersionedQuery Query_addon_for_list_of_selectable_attributes[] = {
+	{70400,
+		"    UNION ALL "
+		"   SELECT DISTINCT pg_catalog.quote_ident(attname) "
+		"     FROM pg_catalog.pg_attribute "
+		"    WHERE attnum > 0 "
+		"      AND NOT attisdropped "
+		"      AND substring(pg_catalog.quote_ident(attname),1,%d)='%s'"
+	},
+	{0, NULL}
+};
+
 /*
  * This is a list of all "things" in Pgsql, which can show up after CREATE or
  * DROP; and there is also a query to get a list of them.
@@ -3768,7 +3807,9 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("IS");
 
 /* SELECT */
-	/* naah . . . */
+	else if (TailMatches("SELECT") || TailMatches("SELECT", "ALL|DISTINCT"))
+		COMPLETE_WITH_VERSIONED_SCHEMA_QUERY(Query_for_list_of_selectable_functions,
+											 Query_addon_for_list_of_selectable_attributes);
 
 /* SET, RESET, SHOW */
 	/* Complete with a variable name */
@@ -4432,7 +4473,8 @@ complete_from_versioned_schema_query(const char *text, int state)
  * where %d is the string length of the text and %s the text itself.
  *
  * If both simple_query and schema_query are non-NULL, then we construct
- * a schema query and append the (uninterpreted) string simple_query to it.
+ * a schema query and append the simple_query to it, replacing the %d and %s
+ * as described above.
  *
  * It is assumed that strings should be escaped to become SQL literals
  * (that is, what is in the query is actually ... '%s' ...)
@@ -4579,21 +4621,22 @@ _complete_from_query(const char *simple_query,
 							  " WHERE substring(pg_catalog.quote_ident(nspname) || '.',1,%d) ="
 							  " substring('%s',1,pg_catalog.length(pg_catalog.quote_ident(nspname))+1)) = 1",
 							  char_length, e_text);
-
-			/* If an addon query was provided, use it */
-			if (simple_query)
-				appendPQExpBuffer(&query_buffer, "\n%s", simple_query);
 		}
 		else
 		{
 			Assert(simple_query);
-			/* simple_query is an sprintf-style format string */
-			appendPQExpBuffer(&query_buffer, simple_query,
-							  char_length, e_text,
-							  e_info_charp, e_info_charp,
-							  e_info_charp2, e_info_charp2);
 		}
 
+		/*
+		 * simple_query is an sprintf-style format string (or it could be NULL, but
+		 * only if this is a schema query with no addon).
+		 */
+		if (simple_query)
+			appendPQExpBuffer(&query_buffer, simple_query,
+					  char_length, e_text,
+					  e_info_charp, e_info_charp,
+					  e_info_charp2, e_info_charp2);
+
 		/* Limit the number of records in the result */
 		appendPQExpBuffer(&query_buffer, "\nLIMIT %d",
 						  completion_max_records);
-- 
2.31.1