v6-0001-Supporting-changes-for-pg_get_tablespace_ddl-func.patch

From 11831687a0324aa88d13716ec7f051a80a42f8e1 Mon Sep 17 00:00:00 2001
From: Manni Wood <manni.wood@enterprisedb.com>
Date: Thu, 6 Nov 2025 14:03:02 -0600
Subject: [PATCH v6 1/2] Supporting changes for pg_get_tablespace_ddl function
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Moving core logic of pg_tablespace_location() to new generic function
get_tablespace_loc_string()

Authors: Manni Wood <manni.wood@enterprisedb.com> and Nishant Sharma
<nishant.sharma@enterprisedb.com>
Reviewers: Vaibhav Dalvi, Ian Barwick, Jim Jones, Álvaro Herrera
Discussion:
https://www.postgresql.org/message-id/flat/CAKWEB6rmnmGKUA87Zmq-s=b3Scsnj02C0kObQjnbL2ajfPWGEw@mail.gmail.com
---
 src/backend/utils/adt/misc.c      | 62 ++----------------------
 src/backend/utils/adt/ruleutils.c | 79 +++++++++++++++++++++++++++++++
 src/include/utils/ruleutils.h     |  2 +
 3 files changed, 85 insertions(+), 58 deletions(-)

diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index fa1cb675027..cb99d7435eb 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -315,66 +315,12 @@ Datum
 pg_tablespace_location(PG_FUNCTION_ARGS)
 {
 	Oid			tablespaceOid = PG_GETARG_OID(0);
-	char		sourcepath[MAXPGPATH];
-	char		targetpath[MAXPGPATH];
-	int			rllen;
-	struct stat st;
+	char	   *tablespaceLoc;
 
-	/*
-	 * It's useful to apply this function to pg_class.reltablespace, wherein
-	 * zero means "the database's default tablespace".  So, rather than
-	 * throwing an error for zero, we choose to assume that's what is meant.
-	 */
-	if (tablespaceOid == InvalidOid)
-		tablespaceOid = MyDatabaseTableSpace;
-
-	/*
-	 * Return empty string for the cluster's default tablespaces
-	 */
-	if (tablespaceOid == DEFAULTTABLESPACE_OID ||
-		tablespaceOid == GLOBALTABLESPACE_OID)
-		PG_RETURN_TEXT_P(cstring_to_text(""));
-
-	/*
-	 * Find the location of the tablespace by reading the symbolic link that
-	 * is in pg_tblspc/<oid>.
-	 */
-	snprintf(sourcepath, sizeof(sourcepath), "%s/%u", PG_TBLSPC_DIR, tablespaceOid);
-
-	/*
-	 * Before reading the link, check if the source path is a link or a
-	 * junction point.  Note that a directory is possible for a tablespace
-	 * created with allow_in_place_tablespaces enabled.  If a directory is
-	 * found, a relative path to the data directory is returned.
-	 */
-	if (lstat(sourcepath, &st) < 0)
-	{
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not stat file \"%s\": %m",
-						sourcepath)));
-	}
-
-	if (!S_ISLNK(st.st_mode))
-		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-
-	/*
-	 * In presence of a link or a junction point, return the path pointing to.
-	 */
-	rllen = readlink(sourcepath, targetpath, sizeof(targetpath));
-	if (rllen < 0)
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not read symbolic link \"%s\": %m",
-						sourcepath)));
-	if (rllen >= sizeof(targetpath))
-		ereport(ERROR,
-				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-				 errmsg("symbolic link \"%s\" target is too long",
-						sourcepath)));
-	targetpath[rllen] = '\0';
+	/* Get LOCATION string from its OID */
+	tablespaceLoc = get_tablespace_loc_string(tablespaceOid);
 
-	PG_RETURN_TEXT_P(cstring_to_text(targetpath));
+	PG_RETURN_TEXT_P(cstring_to_text(tablespaceLoc));
 }
 
 /*
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 556ab057e5a..b15d85c5477 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -18,6 +18,7 @@
 #include <ctype.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <sys/stat.h>
 
 #include "access/amapi.h"
 #include "access/htup_details.h"
@@ -13743,3 +13744,81 @@ get_range_partbound_string(List *bound_datums)
 
 	return buf.data;
 }
+
+/*
+ * get_tablespace_loc_string - get location for a tablespace in string. This is
+ * internal version which helps pg_tablespace_location() and others.
+ */
+char *
+get_tablespace_loc_string(Oid tablespaceOid)
+{
+	char		sourcepath[MAXPGPATH] = { '\0' };
+	char		targetpath[MAXPGPATH] = { '\0' };
+	int			rllen;
+	struct stat st;
+	StringInfoData buf;
+
+	initStringInfo(&buf);
+	appendStringInfoString(&buf, "");
+
+	/*
+	 * It's useful to apply this function to pg_class.reltablespace, wherein
+	 * zero means "the database's default tablespace".  So, rather than
+	 * throwing an error for zero, we choose to assume that's what is meant.
+	 */
+	if (tablespaceOid == InvalidOid)
+		tablespaceOid = MyDatabaseTableSpace;
+
+	/*
+	 * Return empty string for the cluster's default tablespaces
+	 */
+	if (tablespaceOid == DEFAULTTABLESPACE_OID ||
+		tablespaceOid == GLOBALTABLESPACE_OID)
+		return buf.data;
+
+	/*
+	 * Find the location of the tablespace by reading the symbolic link that
+	 * is in pg_tblspc/<oid>.
+	 */
+	snprintf(sourcepath, sizeof(sourcepath), "%s/%u", PG_TBLSPC_DIR, tablespaceOid);
+
+	/*
+	 * Before reading the link, check if the source path is a link or a
+	 * junction point.  Note that a directory is possible for a tablespace
+	 * created with allow_in_place_tablespaces enabled.  If a directory is
+	 * found, a relative path to the data directory is returned.
+	 */
+	if (lstat(sourcepath, &st) < 0)
+	{
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not stat file \"%s\": %m",
+						sourcepath)));
+	}
+
+	if (!S_ISLNK(st.st_mode))
+	{
+		appendStringInfoString(&buf, sourcepath);
+		return buf.data;
+	}
+
+	/*
+	 * In presence of a link or a junction point, return the path pointing to.
+	 */
+	rllen = readlink(sourcepath, targetpath, sizeof(targetpath));
+	if (rllen < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read symbolic link \"%s\": %m",
+						sourcepath)));
+	if (rllen >= sizeof(targetpath))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("symbolic link \"%s\" target is too long",
+						sourcepath)));
+	targetpath[rllen] = '\0';
+
+	appendStringInfoString(&buf, targetpath);
+
+	return buf.data;
+}
diff --git a/src/include/utils/ruleutils.h b/src/include/utils/ruleutils.h
index 7ba7d887914..6d74485f32a 100644
--- a/src/include/utils/ruleutils.h
+++ b/src/include/utils/ruleutils.h
@@ -54,4 +54,6 @@ extern char *get_range_partbound_string(List *bound_datums);
 
 extern char *pg_get_statisticsobjdef_string(Oid statextid);
 
+extern char *get_tablespace_loc_string(Oid tablespaceOid);
+
 #endif							/* RULEUTILS_H */
-- 
2.51.2