Fix O(N^2) behavior in pg_dump for large numbers of owned sequences.

The loop that matched owned sequences to their owning tables required time
proportional to number of owned sequences times number of tables; although
this work was only expended in selective-dump situations, which is probably
why the issue wasn't recognized long since.  Refactor slightly so that we
can perform this work after the index array for findTableByOid has been
set up, reducing the time to O(M log N).

Per gripe from Mike Roest.  Since this is a longstanding performance bug,
backpatch to all supported versions.

3 files changed, 27 insertions, 18 deletions

diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 54451fcafcd..d52566d64e4 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -116,6 +116,9 @@ getSchemaData(int *numTablesPtr)
 	tblinfo = getTables(&numTables);
 	tblinfoindex = buildIndexArray(tblinfo, numTables, sizeof(TableInfo));
 
+	/* Do this after we've built tblinfoindex */
+	getOwnedSeqs(tblinfo, numTables);
+
 	if (g_verbose)
 		write_msg(NULL, "reading extensions\n");
 	extinfo = getExtensions(&numExtensions);
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index fcfc19b9668..a4c6d420ec6 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4303,38 +4303,43 @@ getTables(int *numTables)
 
 	PQclear(res);
 
+	destroyPQExpBuffer(query);
+
+	return tblinfo;
+}
+
+/*
+ * getOwnedSeqs
+ *	  identify owned sequences and mark them as dumpable if owning table is
+ *
+ * We used to do this in getTables(), but it's better to do it after the
+ * index used by findTableByOid() has been set up.
+ */
+void
+getOwnedSeqs(TableInfo tblinfo[], int numTables)
+{
+	int			i;
+
 	/*
 	 * Force sequences that are "owned" by table columns to be dumped whenever
 	 * their owning table is being dumped.
 	 */
-	for (i = 0; i < ntups; i++)
+	for (i = 0; i < numTables; i++)
 	{
 		TableInfo  *seqinfo = &tblinfo[i];
-		int			j;
+		TableInfo  *owning_tab;
 
 		if (!OidIsValid(seqinfo->owning_tab))
 			continue;			/* not an owned sequence */
 		if (seqinfo->dobj.dump)
 			continue;			/* no need to search */
-
-		/* can't use findTableByOid yet, unfortunately */
-		for (j = 0; j < ntups; j++)
+		owning_tab = findTableByOid(seqinfo->owning_tab);
+		if (owning_tab && owning_tab->dobj.dump)
 		{
-			if (tblinfo[j].dobj.catId.oid == seqinfo->owning_tab)
-			{
-				if (tblinfo[j].dobj.dump)
-				{
-					seqinfo->interesting = true;
-					seqinfo->dobj.dump = true;
-				}
-				break;
-			}
+			seqinfo->interesting = true;
+			seqinfo->dobj.dump = true;
 		}
 	}
-
-	destroyPQExpBuffer(query);
-
-	return tblinfo;
 }
 
 /*
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 1539685587e..37b19d2f12e 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -540,6 +540,7 @@ extern OpfamilyInfo *getOpfamilies(int *numOpfamilies);
 extern CollInfo *getCollations(int *numCollations);
 extern ConvInfo *getConversions(int *numConversions);
 extern TableInfo *getTables(int *numTables);
+extern void getOwnedSeqs(TableInfo tblinfo[], int numTables);
 extern InhInfo *getInherits(int *numInherits);
 extern void getIndexes(TableInfo tblinfo[], int numTables);
 extern void getConstraints(TableInfo tblinfo[], int numTables);