Hi, Robert Haas <robertmh...@gmail.com> writes: > On Sun, Nov 13, 2011 at 8:57 PM, Robert Haas <robertmh...@gmail.com> wrote: >> In the -M extended case, we take a snapshot from exec_parse_message(), >> and the same two in the exec_bind_message() call that are taken in the >> -M prepared case. So reducing the prepared case from two snapshots to >> one will reduce the extended case from three snapshots to two, thus >> saving one snapshot per query regardless of how it's executed.
I like the idea and I think it's better semantics to use the same snapshot for planning and executing in the simple query case. I didn't try to reproduce the performance benefits seen by Robert here, nor did I tried to double check to compilation warnings etc. I guess that reviewing a commiter's patch allows for being not as thorough :) > + /* Done with the snapshot used for parameter I/O and parsing/planning */ > + if (snapshot_set) > + PopActiveSnapshot(); This comment needs adjusting. > diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c > index 466727b..c41272b 100644 > --- a/src/backend/tcop/pquery.c > +++ b/src/backend/tcop/pquery.c > @@ -455,7 +455,7 @@ FetchStatementTargetList(Node *stmt) > * tupdesc (if any) is known. > */ > void > -PortalStart(Portal portal, ParamListInfo params, Snapshot snapshot) > +PortalStart(Portal portal, ParamListInfo params, bool use_active_snapshot) You need to be editing the comments for this function. To be specific you didn't update this text: * The caller can optionally pass a snapshot to be used; pass InvalidSnapshot * for the normal behavior of setting a new snapshot. This parameter is * presently ignored for non-PORTAL_ONE_SELECT portals (it's only intended * to be used for cursors). Regards, -- Dimitri Fontaine http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers