Prevent adding relations to a concurrently dropped schema.

[postgresql] / src / backend / parser / parse_utilcmd.c

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index 335bdc6b0754aabb0bbcac43dcfeb8c794817c32..99157c534934a5418d52354e6746814bc71cf0c2 100644 (file)
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -146,6 +146,7 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
        List       *save_alist;
        ListCell   *elements;
        Oid                     namespaceid;
+       Oid                     existing_relid;
 
        /*
         * We must not scribble on the passed-in CreateStmt, so copy it.  (This is
@@ -155,30 +156,25 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 
        /*
         * Look up the creation namespace.      This also checks permissions on the
-        * target namespace, so that we throw any permissions error as early as
-        * possible.
+        * target namespace, locks it against concurrent drops, checks for a
+        * preexisting relation in that namespace with the same name, and updates
+        * stmt->relation->relpersistence if the select namespace is temporary.
         */
-       namespaceid = RangeVarGetAndCheckCreationNamespace(stmt->relation);
-       RangeVarAdjustRelationPersistence(stmt->relation, namespaceid);
+       namespaceid =
+               RangeVarGetAndCheckCreationNamespace(stmt->relation, NoLock,
+                                                                                        &existing_relid);
 
        /*
         * If the relation already exists and the user specified "IF NOT EXISTS",
         * bail out with a NOTICE.
         */
-       if (stmt->if_not_exists)
+       if (stmt->if_not_exists && OidIsValid(existing_relid))
        {
-               Oid                     existing_relid;
-
-               existing_relid = get_relname_relid(stmt->relation->relname,
-                                                                                  namespaceid);
-               if (existing_relid != InvalidOid)
-               {
-                       ereport(NOTICE,
-                                       (errcode(ERRCODE_DUPLICATE_TABLE),
-                                        errmsg("relation \"%s\" already exists, skipping",
-                                                       stmt->relation->relname)));
-                       return NIL;
-               }
+               ereport(NOTICE,
+                               (errcode(ERRCODE_DUPLICATE_TABLE),
+                                errmsg("relation \"%s\" already exists, skipping",
+                                               stmt->relation->relname)));
+               return NIL;
        }
 
        /*