From a7de3dc5c346e07e0439275982569996e645b3c2 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Wed, 20 Jan 2016 13:46:50 -0500 Subject: Support multi-stage aggregation. Aggregate nodes now have two new modes: a "partial" mode where they output the unfinalized transition state, and a "finalize" mode where they accept unfinalized transition states rather than individual values as input. These new modes are not used anywhere yet, but they will be necessary for parallel aggregation. The infrastructure also figures to be useful for cases where we want to aggregate local data and remote data via the FDW interface, and want to bring back partial aggregates from the remote side that can then be combined with locally generated partial aggregates to produce the final value. It may also be useful even when neither FDWs nor parallelism are in play, as explained in the comments in nodeAgg.c. David Rowley and Simon Riggs, reviewed by KaiGai Kohei, Heikki Linnakangas, Haribabu Kommi, and me. --- src/backend/parser/parse_agg.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) (limited to 'src/backend/parser/parse_agg.c') diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c index b718169dffb..b790bb27c5d 100644 --- a/src/backend/parser/parse_agg.c +++ b/src/backend/parser/parse_agg.c @@ -1927,6 +1927,42 @@ build_aggregate_transfn_expr(Oid *agg_input_types, } } +/* + * Like build_aggregate_transfn_expr, but creates an expression tree for the + * combine function of an aggregate, rather than the transition function. + */ +void +build_aggregate_combinefn_expr(Oid agg_state_type, + Oid agg_input_collation, + Oid combinefn_oid, + Expr **combinefnexpr) +{ + Param *argp; + List *args; + FuncExpr *fexpr; + + /* Build arg list to use in the combinefn FuncExpr node. */ + argp = makeNode(Param); + argp->paramkind = PARAM_EXEC; + argp->paramid = -1; + argp->paramtype = agg_state_type; + argp->paramtypmod = -1; + argp->paramcollid = agg_input_collation; + argp->location = -1; + + /* transition state type is arg 1 and 2 */ + args = list_make2(argp, argp); + + fexpr = makeFuncExpr(combinefn_oid, + agg_state_type, + args, + InvalidOid, + agg_input_collation, + COERCE_EXPLICIT_CALL); + fexpr->funcvariadic = false; + *combinefnexpr = (Expr *) fexpr; +} + /* * Like build_aggregate_transfn_expr, but creates an expression tree for the * final function of an aggregate, rather than the transition function. -- cgit v1.2.3