Fix pg_dump to not emit invalid SQL for an empty operator class.

If an operator class has no operators or functions, and doesn't need
a STORAGE clause, we emitted "CREATE OPERATOR CLASS ... AS ;" which
is syntactically invalid.  Fix by forcing a STORAGE clause to be
emitted anyway in this case.

(At some point we might consider changing the grammar to allow CREATE
OPERATOR CLASS without an opclass_item_list.  But probably we'd want to
omit the AS in that case, so that wouldn't fix this pg_dump issue anyway.)

It's been like this all along, so back-patch to all supported branches.

Daniel Gustafsson, tweaked by me to avoid a dangling-pointer bug

Discussion: https://postgr.es/m/D9E5FC64-7A37-4F3D-B946-7E4FB468F88A@yesql.se

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 053ae0e417160a59f2281475bd3370a2227a9a00..9da9b9e96207bad5fe2a7bf896624c5b7a9c371b 100644 (file)
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -12440,7 +12440,8 @@ dumpOpclass(Archive *fout, OpclassInfo *opcinfo)
        i_opcfamilynsp = PQfnumber(res, "opcfamilynsp");
        i_amname = PQfnumber(res, "amname");
 
-       opcintype = PQgetvalue(res, 0, i_opcintype);
+       /* opcintype may still be needed after we PQclear res */
+       opcintype = pg_strdup(PQgetvalue(res, 0, i_opcintype));
        opckeytype = PQgetvalue(res, 0, i_opckeytype);
        opcdefault = PQgetvalue(res, 0, i_opcdefault);
        /* opcfamily will still be needed after we PQclear res */
@@ -12674,6 +12675,15 @@ dumpOpclass(Archive *fout, OpclassInfo *opcinfo)
 
        PQclear(res);
 
+       /*
+        * If needComma is still false it means we haven't added anything after
+        * the AS keyword.  To avoid printing broken SQL, append a dummy STORAGE
+        * clause with the same datatype.  This isn't sanctioned by the
+        * documentation, but actually DefineOpClass will treat it as a no-op.
+        */
+       if (!needComma)
+               appendPQExpBuffer(q, "STORAGE %s", opcintype);
+
        appendPQExpBufferStr(q, ";\n");
 
        appendPQExpBuffer(labelq, "OPERATOR CLASS %s",
@@ -12701,6 +12711,8 @@ dumpOpclass(Archive *fout, OpclassInfo *opcinfo)
                                        opcinfo->dobj.namespace->dobj.name, opcinfo->rolname,
                                        opcinfo->dobj.catId, 0, opcinfo->dobj.dumpId);
 
+       free(opcintype);
+       free(opcfamily);
        free(amname);
        destroyPQExpBuffer(query);
        destroyPQExpBuffer(q);