Tweak publication fetching in psql

petere · petere · commit a2141c42f9eb · 2017-06-20T12:35:02.000-04:00
Viewing a table with \d in psql also shows the publications at table is
in.  If a publication is concurrently dropped, this shows an error,
because the view pg_publication_tables internally uses
pg_get_publication_tables(), which uses a catalog snapshot.  This can be
particularly annoying if a for-all-tables publication is concurrently
dropped.

To avoid that, write the query in psql differently.  Expose the function
pg_relation_is_publishable() to SQL and write the query using that.
That still has a risk of being affected by concurrent catalog changes,
but in this case it would be a table drop that causes problems, and then
the psql \d command wouldn't be interesting anymore anyway.

Reported-by: Tom Lane &lt;tgl@sss.pgh.pa.us&gt;
diff --git a/src/backend/catalog/pg_publication.c b/src/backend/catalog/pg_publication.c
@@ -105,6 +105,30 @@ is_publishable_class(Oid relid, Form_pg_class reltuple)
 		relid >= FirstNormalObjectId;
 }
 
+
+/*
+ * SQL-callable variant of the above
+ *
+ * This returns null when the relation does not exist.  This is intended to be
+ * used for example in psql to avoid gratuitous errors when there are
+ * concurrent catalog changes.
+ */
+Datum
+pg_relation_is_publishable(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	HeapTuple	tuple;
+	bool		result;
+
+	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
+	if (!tuple)
+		PG_RETURN_NULL();
+	result = is_publishable_class(relid, (Form_pg_class) GETSTRUCT(tuple));
+	ReleaseSysCache(tuple);
+	PG_RETURN_BOOL(result);
+}
+
+
 /*
  * Insert new publication / relation mapping.
  */
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
@@ -2536,12 +2536,16 @@ describeOneTableDetails(const char *schemaname,
 		if (pset.sversion >= 100000)
 		{
 			printfPQExpBuffer(&buf,
-							  "SELECT pub.pubname\n"
-							  " FROM pg_catalog.pg_publication pub,\n"
-				  "      pg_catalog.pg_get_publication_tables(pub.pubname)\n"
-							  "WHERE relid = '%s'\n"
+							  "SELECT pubname\n"
+							  "FROM pg_catalog.pg_publication p\n"
+							  "JOIN pg_catalog.pg_publication_rel pr ON p.oid = pr.prpubid\n"
+							  "WHERE pr.prrelid = '%s'\n"
+							  "UNION ALL\n"
+							  "SELECT pubname\n"
+							  "FROM pg_catalog.pg_publication p\n"
+							  "WHERE p.puballtables AND pg_relation_is_publishable('%s')\n"
 							  "ORDER BY 1;",
-							  oid);
+							  oid, oid);
 
 			result = PSQLexec(buf.data);
 			if (!result)
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201706201
+#define CATALOG_VERSION_NO	201706202
 
 #endif
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
@@ -5436,6 +5436,8 @@ DESCR("get progress for all replication origins");
 /* publications */
 DATA(insert OID = 6119 ( pg_get_publication_tables	PGNSP PGUID 12 1 1000 0 0 f f f f t t s s 1 0 26 "25" "{25,26}" "{i,o}" "{pubname,relid}" _null_ _null_ pg_get_publication_tables _null_ _null_ _null_ ));
 DESCR("get OIDs of tables in a publication");
+DATA(insert OID = 6121 ( pg_relation_is_publishable	PGNSP PGUID 12 1    0 0 0 f f f f t f s s 1 0 16 "2205" _null_ _null_ _null_ _null_ _null_ pg_relation_is_publishable _null_ _null_ _null_ ));
+DESCR("returns whether a relation can be part of a publication");
 
 /* rls */
 DATA(insert OID = 3298 (  row_security_active	   PGNSP PGUID 12 1 0 0 0 f f f f t f s s 1 0 16 "26" _null_ _null_ _null_ _null_ _null_	row_security_active _null_ _null_ _null_ ));
