diff options
Diffstat (limited to 'src/backend/executor')
| -rw-r--r-- | src/backend/executor/nodeAgg.c | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c index 63a687e9869..8f641cc843b 100644 --- a/src/backend/executor/nodeAgg.c +++ b/src/backend/executor/nodeAgg.c @@ -40,12 +40,28 @@ * is used to run finalize functions and compute the output tuple; * this context can be reset once per output tuple. * + * Beginning in PostgreSQL 8.1, the executor's AggState node is passed as + * the fmgr "context" value in all transfunc and finalfunc calls. It is + * not really intended that the transition functions will look into the + * AggState node, but they can use code like + * if (fcinfo->context && IsA(fcinfo->context, AggState)) + * to verify that they are being called by nodeAgg.c and not as ordinary + * SQL functions. The main reason a transition function might want to know + * that is that it can avoid palloc'ing a fixed-size pass-by-ref transition + * value on every call: it can instead just scribble on and return its left + * input. Ordinarily it is completely forbidden for functions to modify + * pass-by-ref inputs, but in the aggregate case we know the left input is + * either the initial transition value or a previous function result, and + * in either case its value need not be preserved. See int8inc() for an + * example. Notice that advance_transition_function() is coded to avoid a + * data copy step when the previous transition value pointer is returned. + * * * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/executor/nodeAgg.c,v 1.128 2005/01/28 19:33:56 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/executor/nodeAgg.c,v 1.129 2005/03/12 20:25:06 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -363,7 +379,7 @@ advance_transition_function(AggState *aggstate, */ /* MemSet(&fcinfo, 0, sizeof(fcinfo)); */ - fcinfo.context = NULL; + fcinfo.context = (void *) aggstate; fcinfo.resultinfo = NULL; fcinfo.isnull = false; @@ -541,6 +557,7 @@ finalize_aggregate(AggState *aggstate, FunctionCallInfoData fcinfo; MemSet(&fcinfo, 0, sizeof(fcinfo)); + fcinfo.context = (void *) aggstate; fcinfo.flinfo = &peraggstate->finalfn; fcinfo.nargs = 1; fcinfo.arg[0] = pergroupstate->transValue; |