Rethink recent fix for pg_dump's handling of extension config tables.

tglsfdc · tglsfdc · commit 0bfe356c5594 · 2020-10-07T12:51:06.000-04:00
Commit 3eb3d3e was a few bricks shy of a load: while it correctly set the table's "interesting" flag when deciding to dump the data of an extension config table, it was not correct to clear that flag if we concluded we shouldn't dump the data. This led to the crash reported in bug #16655, because in fact we'll traverse dumpTableSchema anyway for all extension tables (to see if they have user-added seclabels or RLS policies). The right thing to do is to force "interesting" true in makeTableDataInfo, and otherwise leave the flag alone. (Doing it there is more future-proof in case additional calls are added, and it also avoids setting the flag unnecessarily if that function decides the table is non-dumpable.) This investigation also showed that while only the --inserts code path had an obvious failure in the case considered by 3eb3d3e, the COPY code path also has a problem with not having loaded table subsidiary data. That causes fmtCopyColumnList to silently return an empty string instead of the correct column list. That accidentally mostly works, which perhaps is why we didn't notice this before. It would only fail if the restore column order is different from the dump column order, which only happens in weird inheritance cases, so it's not surprising nobody had hit the case with an extension config table. Nonetheless, it's a bug, and it goes a long way back, not just to v12 where the --inserts code path started to have a problem with this. In hopes of catching such cases a bit sooner in future, add some Asserts that "interesting" has been set in both dumpTableData and dumpTableSchema. Adjust the test case added by 3eb3d3e so that it checks the COPY rather than INSERT form of that bug, allowing it to detect the longer-standing symptom. Per bug #16655 from Cameron Daniel. Back-patch to all supported branches. Discussion: https://postgr.es/m/16655-5c92d6b3a9438137@postgresql.org Discussion: https://postgr.es/m/18048b44-3414-b983-8c7c-9165b177900d@2ndQuadrant.com
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
@@ -1911,6 +1911,9 @@ dumpTableData(Archive *fout, TableDataInfo *tdinfo)
 	DataDumperPtr dumpFn;
 	char	   *copyStmt;
 
+	/* We had better have loaded per-column details about this table */
+	Assert(tbinfo->interesting);
+
 	if (!dopt->dump_inserts)
 	{
 		/* Dump/restore using COPY */
@@ -2064,6 +2067,9 @@ makeTableDataInfo(DumpOptions *dopt, TableInfo *tbinfo, bool oids)
 	addObjectDependency(&tdinfo->dobj, tbinfo->dobj.dumpId);
 
 	tbinfo->dataObj = tdinfo;
+
+	/* Make sure that we'll collect per-column info for this table. */
+	tbinfo->interesting = true;
 }
 
 /*
@@ -13843,6 +13849,9 @@ dumpTableSchema(Archive *fout, TableInfo *tbinfo)
 	int			j,
 				k;
 
+	/* We had better have loaded per-column details about this table */
+	Assert(tbinfo->interesting);
+
 	qrelname = pg_strdup(fmtId(tbinfo->dobj.name));
 	qualrelname = pg_strdup(fmtQualifiedDumpable(tbinfo));
 
