v10-0001-Some-small-preliminaries-for-pg_dump-changes.patch

From c48b11547c6eb95ab217dddc047da5378042452c Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 26 Jan 2024 11:10:00 -0500
Subject: [PATCH v10 1/4] Some small preliminaries for pg_dump changes.

Centralize management of the lo_buf used to hold data while restoring
blobs.  The code previously had each format handler create lo_buf,
which seems rather pointless given that the format handlers all make
it the same way.  Moreover, the format handlers never use lo_buf
directly, making this setup a failure from a separation-of-concerns
standpoint.  Let's move the responsibility into pg_backup_archiver.c,
which is the only module concerned with lo_buf.  The main reason to do
this now is that it allows a centralized fix for the soon-to-be-false
assumption that we never restore blobs in parallel.

Also, get rid of dead code in DropLOIfExists: it's been a long time
since we had any need to be able to restore to a pre-9.0 server.
---
 src/bin/pg_dump/pg_backup_archiver.c  |  9 +++++++++
 src/bin/pg_dump/pg_backup_custom.c    |  7 -------
 src/bin/pg_dump/pg_backup_db.c        | 27 +++++----------------------
 src/bin/pg_dump/pg_backup_directory.c |  6 ------
 src/bin/pg_dump/pg_backup_null.c      |  4 ----
 src/bin/pg_dump/pg_backup_tar.c       |  4 ----
 6 files changed, 14 insertions(+), 43 deletions(-)

diff --git a/src/bin/pg_dump/pg_backup_archiver.c b/src/bin/pg_dump/pg_backup_archiver.c
index 256d1e35a4..26c2c684c8 100644
--- a/src/bin/pg_dump/pg_backup_archiver.c
+++ b/src/bin/pg_dump/pg_backup_archiver.c
@@ -1343,6 +1343,12 @@ StartRestoreLO(ArchiveHandle *AH, Oid oid, bool drop)
 	AH->loCount++;
 
 	/* Initialize the LO Buffer */
+	if (AH->lo_buf == NULL)
+	{
+		/* First time through (in this process) so allocate the buffer */
+		AH->lo_buf_size = LOBBUFSIZE;
+		AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE);
+	}
 	AH->lo_buf_used = 0;
 
 	pg_log_info("restoring large object with OID %u", oid);
@@ -4748,6 +4754,9 @@ CloneArchive(ArchiveHandle *AH)
 	/* clone has its own error count, too */
 	clone->public.n_errors = 0;
 
+	/* clones should not share lo_buf */
+	clone->lo_buf = NULL;
+
 	/*
 	 * Connect our new clone object to the database, using the same connection
 	 * parameters used for the original connection.
diff --git a/src/bin/pg_dump/pg_backup_custom.c b/src/bin/pg_dump/pg_backup_custom.c
index b576b29924..7c6ac89dd4 100644
--- a/src/bin/pg_dump/pg_backup_custom.c
+++ b/src/bin/pg_dump/pg_backup_custom.c
@@ -140,10 +140,6 @@ InitArchiveFmt_Custom(ArchiveHandle *AH)
 	ctx = (lclContext *) pg_malloc0(sizeof(lclContext));
 	AH->formatData = (void *) ctx;
 
-	/* Initialize LO buffering */
-	AH->lo_buf_size = LOBBUFSIZE;
-	AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE);
-
 	/*
 	 * Now open the file
 	 */
@@ -902,9 +898,6 @@ _Clone(ArchiveHandle *AH)
 	 * share knowledge about where the data blocks are across threads.
 	 * _PrintTocData has to be careful about the order of operations on that
 	 * state, though.
-	 *
-	 * Note: we do not make a local lo_buf because we expect at most one BLOBS
-	 * entry per archive, so no parallelism is possible.
 	 */
 }
 
diff --git a/src/bin/pg_dump/pg_backup_db.c b/src/bin/pg_dump/pg_backup_db.c
index f766b65059..b297ca049d 100644
--- a/src/bin/pg_dump/pg_backup_db.c
+++ b/src/bin/pg_dump/pg_backup_db.c
@@ -544,26 +544,9 @@ CommitTransaction(Archive *AHX)
 void
 DropLOIfExists(ArchiveHandle *AH, Oid oid)
 {
-	/*
-	 * If we are not restoring to a direct database connection, we have to
-	 * guess about how to detect whether the LO exists.  Assume new-style.
-	 */
-	if (AH->connection == NULL ||
-		PQserverVersion(AH->connection) >= 90000)
-	{
-		ahprintf(AH,
-				 "SELECT pg_catalog.lo_unlink(oid) "
-				 "FROM pg_catalog.pg_largeobject_metadata "
-				 "WHERE oid = '%u';\n",
-				 oid);
-	}
-	else
-	{
-		/* Restoring to pre-9.0 server, so do it the old way */
-		ahprintf(AH,
-				 "SELECT CASE WHEN EXISTS("
-				 "SELECT 1 FROM pg_catalog.pg_largeobject WHERE loid = '%u'"
-				 ") THEN pg_catalog.lo_unlink('%u') END;\n",
-				 oid, oid);
-	}
+	ahprintf(AH,
+			 "SELECT pg_catalog.lo_unlink(oid) "
+			 "FROM pg_catalog.pg_largeobject_metadata "
+			 "WHERE oid = '%u';\n",
+			 oid);
 }
diff --git a/src/bin/pg_dump/pg_backup_directory.c b/src/bin/pg_dump/pg_backup_directory.c
index dba57443e8..de3cfea02e 100644
--- a/src/bin/pg_dump/pg_backup_directory.c
+++ b/src/bin/pg_dump/pg_backup_directory.c
@@ -143,10 +143,6 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 	ctx->dataFH = NULL;
 	ctx->LOsTocFH = NULL;
 
-	/* Initialize LO buffering */
-	AH->lo_buf_size = LOBBUFSIZE;
-	AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE);
-
 	/*
 	 * Now open the TOC file
 	 */
@@ -823,8 +819,6 @@ _Clone(ArchiveHandle *AH)
 	ctx = (lclContext *) AH->formatData;
 
 	/*
-	 * Note: we do not make a local lo_buf because we expect at most one BLOBS
-	 * entry per archive, so no parallelism is possible.  Likewise,
 	 * TOC-entry-local state isn't an issue because any one TOC entry is
 	 * touched by just one worker child.
 	 */
diff --git a/src/bin/pg_dump/pg_backup_null.c b/src/bin/pg_dump/pg_backup_null.c
index 08f096251b..776f057770 100644
--- a/src/bin/pg_dump/pg_backup_null.c
+++ b/src/bin/pg_dump/pg_backup_null.c
@@ -63,10 +63,6 @@ InitArchiveFmt_Null(ArchiveHandle *AH)
 	AH->ClonePtr = NULL;
 	AH->DeClonePtr = NULL;
 
-	/* Initialize LO buffering */
-	AH->lo_buf_size = LOBBUFSIZE;
-	AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE);
-
 	/*
 	 * Now prevent reading...
 	 */
diff --git a/src/bin/pg_dump/pg_backup_tar.c b/src/bin/pg_dump/pg_backup_tar.c
index aad88ad559..4cb9707e63 100644
--- a/src/bin/pg_dump/pg_backup_tar.c
+++ b/src/bin/pg_dump/pg_backup_tar.c
@@ -156,10 +156,6 @@ InitArchiveFmt_Tar(ArchiveHandle *AH)
 	ctx->filePos = 0;
 	ctx->isSpecialScript = 0;
 
-	/* Initialize LO buffering */
-	AH->lo_buf_size = LOBBUFSIZE;
-	AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE);
-
 	/*
 	 * Now open the tar file, and load the TOC if we're in read mode.
 	 */
-- 
2.39.3