Fix STRICT check for strict aggregates with NULL ORDER BY columns.

I (Andres) broke this unintentionally in 69c3936, by checking
strictness for all input expressions computed for an aggregate, rather
than just the input for the aggregate transition function.

Reported-By: Ondřej Bouda
Bisected-By: Tom Lane
Diagnosed-By: Andrew Gierth
Discussion: https://postgr.es/m/2a505161-2727-2473-7c46-591ed108ac52@email.cz
Backpatch: 11-, like 69c3936

Author: anarazel

src/backend/executor/execExpr.c

@@ -3028,7 +3028,7 @@ ExecBuildAggTrans(AggState *aggstate, AggStatePerPhase phase,
 			scratch.opcode = EEOP_AGG_STRICT_INPUT_CHECK;
 			scratch.d.agg_strict_input_check.nulls = strictnulls;
 			scratch.d.agg_strict_input_check.jumpnull = -1; /* adjust later */
-			scratch.d.agg_strict_input_check.nargs = numInputs;
+			scratch.d.agg_strict_input_check.nargs = pertrans->numTransInputs;
 			ExprEvalPushStep(state, &scratch);
 			adjust_bailout = lappend_int(adjust_bailout,
 										 state->steps_len - 1);

src/test/regress/expected/aggregates.out

@@ -2101,3 +2101,18 @@ SELECT dense_rank(x) WITHIN GROUP (ORDER BY x) FROM (VALUES (1),(1),(2),(2),(3),
           1
 (3 rows)
 
+-- Ensure that the STRICT checks for aggregates does not take NULLness
+-- of ORDER BY columns into account. See bug report around
+-- 2a505161-2727-2473-7c46-591ed108ac52@email.cz
+SELECT min(x ORDER BY y) FROM (VALUES(1, NULL)) AS d(x,y);
+ min 
+-----
+   1
+(1 row)
+
+SELECT min(x ORDER BY y) FROM (VALUES(1, 2)) AS d(x,y);
+ min 
+-----
+   1
+(1 row)
+

src/test/regress/sql/aggregates.sql

@@ -928,3 +928,10 @@ ROLLBACK;
 
 -- test coverage for dense_rank
 SELECT dense_rank(x) WITHIN GROUP (ORDER BY x) FROM (VALUES (1),(1),(2),(2),(3),(3)) v(x) GROUP BY (x) ORDER BY 1;
+
+
+-- Ensure that the STRICT checks for aggregates does not take NULLness
+-- of ORDER BY columns into account. See bug report around
+-- 2a505161-2727-2473-7c46-591ed108ac52@email.cz
+SELECT min(x ORDER BY y) FROM (VALUES(1, NULL)) AS d(x,y);
+SELECT min(x ORDER BY y) FROM (VALUES(1, 2)) AS d(x,y);