expression eval: Reduce number of steps for agg transition invocations.

Do so by combining the various steps that are part of aggregate
transition function invocation into one larger step. As some of the
current steps are only necessary for some aggregates, have one variant
of the aggregate transition step for each possible combination.

To avoid further manual copies of code in the different transition
step implementations, move most of the code into helper functions
marked as "always inline".

The benefit of this change is an increase in performance when
aggregating lots of rows. This comes in part due to the reduced number
of indirect jumps due to the reduced number of steps, and in part by
reducing redundant setup code across steps. This mainly benefits
interpreted execution, but the code generated by JIT is also improved
a bit.

As a nice side-effect it also ends up making the code a bit simpler.

A small additional optimization is removing the need to set
aggstate->curaggcontext before calling ExecAggInitGroup, choosing to
instead passign curaggcontext as an argument. It was, in contrast to
other aggregate related functions, only needed to fetch a memory
context to copy the transition value into.

Author: Andres Freund
Discussion:
   https://postgr.es/m/[email protected]
   https://postgr.es/m/[email protected]

1 files changed, 9 insertions, 25 deletions

diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h
index 73a2ca8c6dd..8bbf6621da0 100644
--- a/src/include/executor/execExpr.h
+++ b/src/include/executor/execExpr.h
@@ -225,10 +225,12 @@ typedef enum ExprEvalOp
 	EEOP_AGG_DESERIALIZE,
 	EEOP_AGG_STRICT_INPUT_CHECK_ARGS,
 	EEOP_AGG_STRICT_INPUT_CHECK_NULLS,
-	EEOP_AGG_INIT_TRANS,
-	EEOP_AGG_STRICT_TRANS_CHECK,
+	EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL,
+	EEOP_AGG_PLAIN_TRANS_STRICT_BYVAL,
 	EEOP_AGG_PLAIN_TRANS_BYVAL,
-	EEOP_AGG_PLAIN_TRANS,
+	EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYREF,
+	EEOP_AGG_PLAIN_TRANS_STRICT_BYREF,
+	EEOP_AGG_PLAIN_TRANS_BYREF,
 	EEOP_AGG_ORDERED_TRANS_DATUM,
 	EEOP_AGG_ORDERED_TRANS_TUPLE,
 
@@ -620,27 +622,8 @@ typedef struct ExprEvalStep
 			int			jumpnull;
 		}			agg_strict_input_check;
 
-		/* for EEOP_AGG_INIT_TRANS */
-		struct
-		{
-			AggStatePerTrans pertrans;
-			ExprContext *aggcontext;
-			int			setno;
-			int			transno;
-			int			setoff;
-			int			jumpnull;
-		}			agg_init_trans;
-
-		/* for EEOP_AGG_STRICT_TRANS_CHECK */
-		struct
-		{
-			int			setno;
-			int			transno;
-			int			setoff;
-			int			jumpnull;
-		}			agg_strict_trans_check;
-
-		/* for EEOP_AGG_{PLAIN,ORDERED}_TRANS* */
+		/* for EEOP_AGG_PLAIN_TRANS_[INIT_][STRICT_]{BYVAL,BYREF} */
+		/* for EEOP_AGG_ORDERED_TRANS_{DATUM,TUPLE} */
 		struct
 		{
 			AggStatePerTrans pertrans;
@@ -750,7 +733,8 @@ extern void ExecEvalWholeRowVar(ExprState *state, ExprEvalStep *op,
 extern void ExecEvalSysVar(ExprState *state, ExprEvalStep *op,
 						   ExprContext *econtext, TupleTableSlot *slot);
 
-extern void ExecAggInitGroup(AggState *aggstate, AggStatePerTrans pertrans, AggStatePerGroup pergroup);
+extern void ExecAggInitGroup(AggState *aggstate, AggStatePerTrans pertrans, AggStatePerGroup pergroup,
+							 ExprContext *aggcontext);
 extern Datum ExecAggTransReparent(AggState *aggstate, AggStatePerTrans pertrans,
 								  Datum newValue, bool newValueIsNull,
 								  Datum oldValue, bool oldValueIsNull);