pg_dump should use current_database() instead of PQdb()

From eaccc63b2f9943633f957f80d67acf54ad70098d Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Tue, 10 Apr 2018 12:32:05 -0400
Subject: [PATCH] pg_dump: Use current_database() instead of PQdb()

For querying pg_database about information about the database being
dumped, look up by using current_database() instead of the value
obtained from PQdb().  When using a connection proxy, the value from
PQdb() might not be the real name of the database.
---
 src/bin/pg_dump/pg_dump.c | 52 +++++++++++++++++----------------------
 1 file changed, 22 insertions(+), 30 deletions(-)

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index d066f4f00b..52698cb3b6 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -251,7 +251,7 @@ static char *convertRegProcReference(Archive *fout,
 						const char *proc);
 static char *getFormattedOperatorName(Archive *fout, const char *oproid);
 static char *convertTSFunction(Archive *fout, Oid funcOid);
-static Oid	findLastBuiltinOid_V71(Archive *fout, const char *);
+static Oid	findLastBuiltinOid_V71(Archive *fout);
 static char *getFormattedTypeName(Archive *fout, Oid oid, OidOptions opts);
 static void getBlobs(Archive *fout);
 static void dumpBlob(Archive *fout, BlobInfo *binfo);
@@ -735,8 +735,7 @@ main(int argc, char **argv)
 	 * With 8.1 and above, we can just use FirstNormalObjectId - 1.
 	 */
 	if (fout->remoteVersion < 80100)
-		g_last_builtin_oid = findLastBuiltinOid_V71(fout,
-													PQdb(GetConnection(fout)));
+		g_last_builtin_oid = findLastBuiltinOid_V71(fout);
 	else
 		g_last_builtin_oid = FirstNormalObjectId - 1;
 
@@ -2538,6 +2537,7 @@ dumpDatabase(Archive *fout)
 	PGresult   *res;
 	int			i_tableoid,
 				i_oid,
+				i_datname,
 				i_dba,
 				i_encoding,
 				i_collate,
@@ -2565,16 +2565,13 @@ dumpDatabase(Archive *fout)
 				minmxid;
 	char	   *qdatname;
 
-	datname = PQdb(conn);
-	qdatname = pg_strdup(fmtId(datname));
-
 	if (g_verbose)
 		write_msg(NULL, "saving database definition\n");
 
 	/* Fetch the database-level properties for this database */
 	if (fout->remoteVersion >= 90600)
 	{
-		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, "
+		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, datname, "
 						  "(%s datdba) AS dba, "
 						  "pg_encoding_to_char(encoding) AS encoding, "
 						  "datcollate, datctype, datfrozenxid, datminmxid, "
@@ -2591,13 +2588,12 @@ dumpDatabase(Archive *fout)
 						  "shobj_description(oid, 'pg_database') AS description "
 
 						  "FROM pg_database "
-						  "WHERE datname = ",
+						  "WHERE datname = current_database()",
 						  username_subquery);
-		appendStringLiteralAH(dbQry, datname, fout);
 	}
 	else if (fout->remoteVersion >= 90300)
 	{
-		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, "
+		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, datname, "
 						  "(%s datdba) AS dba, "
 						  "pg_encoding_to_char(encoding) AS encoding, "
 						  "datcollate, datctype, datfrozenxid, datminmxid, "
@@ -2606,13 +2602,12 @@ dumpDatabase(Archive *fout)
 						  "shobj_description(oid, 'pg_database') AS description "
 
 						  "FROM pg_database "
-						  "WHERE datname = ",
+						  "WHERE datname = current_database()",
 						  username_subquery);
-		appendStringLiteralAH(dbQry, datname, fout);
 	}
 	else if (fout->remoteVersion >= 80400)
 	{
-		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, "
+		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, datname, "
 						  "(%s datdba) AS dba, "
 						  "pg_encoding_to_char(encoding) AS encoding, "
 						  "datcollate, datctype, datfrozenxid, 0 AS datminmxid, "
@@ -2621,13 +2616,12 @@ dumpDatabase(Archive *fout)
 						  "shobj_description(oid, 'pg_database') AS description "
 
 						  "FROM pg_database "
-						  "WHERE datname = ",
+						  "WHERE datname = current_database()",
 						  username_subquery);
-		appendStringLiteralAH(dbQry, datname, fout);
 	}
 	else if (fout->remoteVersion >= 80200)
 	{
-		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, "
+		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, datname, "
 						  "(%s datdba) AS dba, "
 						  "pg_encoding_to_char(encoding) AS encoding, "
 						  "NULL AS datcollate, NULL AS datctype, datfrozenxid, 0 AS datminmxid, "
@@ -2636,13 +2630,12 @@ dumpDatabase(Archive *fout)
 						  "shobj_description(oid, 'pg_database') AS description "
 
 						  "FROM pg_database "
-						  "WHERE datname = ",
+						  "WHERE datname = current_database()",
 						  username_subquery);
-		appendStringLiteralAH(dbQry, datname, fout);
 	}
 	else
 	{
-		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, "
+		appendPQExpBuffer(dbQry, "SELECT tableoid, oid, datname, "
 						  "(%s datdba) AS dba, "
 						  "pg_encoding_to_char(encoding) AS encoding, "
 						  "NULL AS datcollate, NULL AS datctype, datfrozenxid, 0 AS datminmxid, "
@@ -2650,15 +2643,15 @@ dumpDatabase(Archive *fout)
 						  "-1 as datconnlimit, "
 						  "(SELECT spcname FROM pg_tablespace t WHERE t.oid = dattablespace) AS tablespace "
 						  "FROM pg_database "
-						  "WHERE datname = ",
+						  "WHERE datname = current_database()",
 						  username_subquery);
-		appendStringLiteralAH(dbQry, datname, fout);
 	}
 
 	res = ExecuteSqlQueryForSingleRow(fout, dbQry->data);
 
 	i_tableoid = PQfnumber(res, "tableoid");
 	i_oid = PQfnumber(res, "oid");
+	i_datname = PQfnumber(res, "datname");
 	i_dba = PQfnumber(res, "dba");
 	i_encoding = PQfnumber(res, "encoding");
 	i_collate = PQfnumber(res, "datcollate");
@@ -2673,6 +2666,7 @@ dumpDatabase(Archive *fout)
 
 	dbCatId.tableoid = atooid(PQgetvalue(res, 0, i_tableoid));
 	dbCatId.oid = atooid(PQgetvalue(res, 0, i_oid));
+	datname = PQgetvalue(res, 0, i_datname);
 	dba = PQgetvalue(res, 0, i_dba);
 	encoding = PQgetvalue(res, 0, i_encoding);
 	collate = PQgetvalue(res, 0, i_collate);
@@ -2685,6 +2679,8 @@ dumpDatabase(Archive *fout)
 	datconnlimit = PQgetvalue(res, 0, i_datconnlimit);
 	tablespace = PQgetvalue(res, 0, i_tablespace);
 
+	qdatname = pg_strdup(fmtId(datname));
+
 	/*
 	 * Prepare the CREATE DATABASE command.  We must specify encoding, locale,
 	 * and tablespace since those can't be altered later.  Other DB properties
@@ -16540,23 +16536,19 @@ dumpTableConstraintComment(Archive *fout, ConstraintInfo *coninfo)
  * find the last built in oid
  *
  * For 7.1 through 8.0, we do this by retrieving datlastsysoid from the
- * pg_database entry for the current database.
+ * pg_database entry for the current database.  (Note: current_database()
+ * requires 7.3; pg_dump requires 8.0 now.)
  */
 static Oid
-findLastBuiltinOid_V71(Archive *fout, const char *dbname)
+findLastBuiltinOid_V71(Archive *fout)
 {
 	PGresult   *res;
 	Oid			last_oid;
-	PQExpBuffer query = createPQExpBuffer();
 
-	resetPQExpBuffer(query);
-	appendPQExpBufferStr(query, "SELECT datlastsysoid from pg_database where datname = ");
-	appendStringLiteralAH(query, dbname, fout);
-
-	res = ExecuteSqlQueryForSingleRow(fout, query->data);
+	res = ExecuteSqlQueryForSingleRow(fout,
+									  "SELECT datlastsysoid FROM pg_database WHERE datname = current_database()");
 	last_oid = atooid(PQgetvalue(res, 0, PQfnumber(res, "datlastsysoid")));
 	PQclear(res);
-	destroyPQExpBuffer(query);
 
 	return last_oid;
 }

base-commit: 4f813c7203e0c08395833b2bd75ac9ccf63c6264
-- 
2.17.0