Enable parallelism for prepared statements and extended query protocol.

Parallel query can't handle running a query only partially rather than
to completion.  However, there seems to be no way to run a statement
prepared via SQL PREPARE other than to completion, so we can enable it
there without a problem.

The situation is more complicated for the extend query protocol.
libpq seems to provide no way to send an Execute message with a
non-zero rowcount, but some other client might.  If that happens, and
a parallel plan was chosen, we'll execute the parallel plan without
using any workers, which may be somewhat inefficient but should still
work.  Hopefully this won't be a problem; users can always set
max_parallel_degree=0 to avoid choosing parallel plans in the first
place.

Amit Kapila, reviewed by me.

diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index cec37ce0405739d42732848ae08eef58dfa3daaa..b01051df9d2f942d14a7d102fec97274f6342c05 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,
-                                          0,           /* default cursor options */
+                                          CURSOR_OPT_PARALLEL_OK,      /* allow parallel mode */
                                           true);       /* fixed result */
 
        /*

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 390816bb9c2615f03f89a1723e93e33dc71be4df..115166b6f6adcd12e1f90bb3164da8b0c7b84149 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -1381,7 +1381,7 @@ exec_parse_message(const char *query_string,      /* string to execute */
                                           numParams,
                                           NULL,
                                           NULL,
-                                          0,           /* default cursor options */
+                                          CURSOR_OPT_PARALLEL_OK,      /* allow parallel mode */
                                           true);       /* fixed result */
 
        /* If we got a cancel signal during analysis, quit */