reduce-pg_upgrade-cache-bloat-wip.patch

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index b8b1888bd3..19f98bdf43 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -16094,6 +16094,12 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 			 tbinfo->relkind == RELKIND_FOREIGN_TABLE ||
 			 tbinfo->relkind == RELKIND_PARTITIONED_TABLE))
 		{
+			bool		firstinhcol = true;
+
+			/*
+			 * Drop any dropped columns.  We don't really expect there to be a
+			 * lot, else this code would be pretty inefficient.
+			 */
 			for (j = 0; j < tbinfo->numatts; j++)
 			{
 				if (tbinfo->attisdropped[j])
@@ -16120,18 +16126,37 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 					appendPQExpBuffer(q, "DROP COLUMN %s;\n",
 									  fmtId(tbinfo->attnames[j]));
 				}
-				else if (!tbinfo->attislocal[j])
+			}
+
+			/*
+			 * Fix up inherited columns.  There could be a lot of these, so we
+			 * do the operation in a single SQL command; otherwise, we risk
+			 * O(N^2) relcache bloat thanks to repeatedly invalidating the
+			 * table's relcache entry.
+			 */
+			for (j = 0; j < tbinfo->numatts; j++)
+			{
+				if (!tbinfo->attisdropped[j] &&
+					!tbinfo->attislocal[j])
 				{
-					appendPQExpBufferStr(q, "\n-- For binary upgrade, recreate inherited column.\n");
-					appendPQExpBufferStr(q, "UPDATE pg_catalog.pg_attribute\n"
-										 "SET attislocal = false\n"
-										 "WHERE attname = ");
+					if (firstinhcol)
+					{
+						appendPQExpBufferStr(q, "\n-- For binary upgrade, recreate inherited columns.\n");
+						appendPQExpBufferStr(q, "UPDATE pg_catalog.pg_attribute\n"
+											 "SET attislocal = false\n"
+											 "WHERE attrelid = ");
+						appendStringLiteralAH(q, qualrelname, fout);
+						appendPQExpBufferStr(q, "::pg_catalog.regclass\n"
+											 "  AND attname IN (");
+						firstinhcol = false;
+					}
+					else
+						appendPQExpBufferStr(q, ", ");
 					appendStringLiteralAH(q, tbinfo->attnames[j], fout);
-					appendPQExpBufferStr(q, "\n  AND attrelid = ");
-					appendStringLiteralAH(q, qualrelname, fout);
-					appendPQExpBufferStr(q, "::pg_catalog.regclass;\n");
 				}
 			}
+			if (!firstinhcol)
+				appendPQExpBufferStr(q, ");\n");
 
 			/*
 			 * Add inherited CHECK constraints, if any.