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

Commit 3eb3d3e78 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 3eb3d3e78, 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 3eb3d3e78 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
index 32908242be2e8e7529e5840f984ea1fd25d13aeb..b30b87ae66dda6498d9ee44de0a4b7f67ade3e8a 100644 (file)
--- 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));