From bdfbfde1b168b3332c4cdac34ac86a80aaf4d442 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 20 Jan 2003 18:55:07 +0000 Subject: IN clauses appearing at top level of WHERE can now be handled as joins. There are two implementation techniques: the executor understands a new JOIN_IN jointype, which emits at most one matching row per left-hand row, or the result of the IN's sub-select can be fed through a DISTINCT filter and then joined as an ordinary relation. Along the way, some minor code cleanup in the optimizer; notably, break out most of the jointree-rearrangement preprocessing in planner.c and put it in a new file prep/prepjointree.c. --- src/backend/executor/nodeHashjoin.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'src/backend/executor/nodeHashjoin.c') diff --git a/src/backend/executor/nodeHashjoin.c b/src/backend/executor/nodeHashjoin.c index 48cf30c21f..d452d3865f 100644 --- a/src/backend/executor/nodeHashjoin.c +++ b/src/backend/executor/nodeHashjoin.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/executor/nodeHashjoin.c,v 1.46 2002/12/30 15:21:20 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/executor/nodeHashjoin.c,v 1.47 2003/01/20 18:54:45 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -95,6 +95,15 @@ ExecHashJoin(HashJoinState *node) node->js.ps.ps_TupFromTlist = false; } + /* + * If we're doing an IN join, we want to return at most one row per + * outer tuple; so we can stop scanning the inner scan if we matched on + * the previous try. + */ + if (node->js.jointype == JOIN_IN && + node->hj_MatchedOuter) + node->hj_NeedNewOuter = true; + /* * Reset per-tuple memory context to free any expression evaluation * storage allocated in the previous tuple cycle. Note this can't @@ -353,6 +362,7 @@ ExecInitHashJoin(HashJoin *node, EState *estate) switch (node->join.jointype) { case JOIN_INNER: + case JOIN_IN: break; case JOIN_LEFT: hjstate->hj_NullInnerTupleSlot = -- cgit v1.2.1