On second thought, disable parallelism for prepared statements.

CREATE TABLE .. AS EXECUTE can turn an apparently read-only query into
a write operation, which parallel query can't handle.  It's a bit of a
shame that requires us to avoid parallel query for queries prepared via
PREPARE in all cases, but for right now it does.

diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index b01051df9d2f942d14a7d102fec97274f6342c05..cec37ce0405739d42732848ae08eef58dfa3daaa 100644 (file)
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -159,7 +159,7 @@ PrepareQuery(PrepareStmt *stmt, const char *queryString)
                                           nargs,
                                           NULL,
                                           NULL,
-                                          CURSOR_OPT_PARALLEL_OK,      /* allow parallel mode */
+                                          0,           /* default cursor options */
                                           true);       /* fixed result */
 
        /*