Fix COPY's handling of transition tables with indexes.

Commit c46c0e5202 failed to pass the
TransitionCaptureState object to ExecARInsertTriggers() in the case
where it's using heap_multi_insert and there are indexes.  Repair.

Thomas Munro, from a report by David Fetter
Discussion: https://postgr.es/m/20170708084213.GA14720%40fetter.org

src/backend/commands/copy.c

@@ -2915,7 +2915,7 @@ CopyFromInsertBatch(CopyState cstate, EState *estate, CommandId mycid,
 									  estate, false, NULL, NIL);
 			ExecARInsertTriggers(estate, resultRelInfo,
 								 bufferedTuples[i],
-								 recheckIndexes, NULL);
+								 recheckIndexes, cstate->transition_capture);
 			list_free(recheckIndexes);
 		}
 	}

src/test/regress/expected/triggers.out

@@ -2156,6 +2156,11 @@ NOTICE:  trigger = child3_delete_trig, old table = (CCC,42,foo)
 -- are really inserted into the parent)
 copy parent (a, b) from stdin;
 NOTICE:  trigger = parent_insert_trig, new table = (AAA,42), (BBB,42), (CCC,42)
+-- same behavior for copy if there is an index (interesting because rows are
+-- captured by a different code path in copy.c if there are indexes)
+create index on parent(b);
+copy parent (a, b) from stdin;
+NOTICE:  trigger = parent_insert_trig, new table = (DDD,42)
 -- DML affecting parent sees tuples collected from children even if
 -- there is no transition table trigger on the children
 drop trigger child1_insert_trig on child1;
@@ -2168,7 +2173,7 @@ drop trigger child3_insert_trig on child3;
 drop trigger child3_update_trig on child3;
 drop trigger child3_delete_trig on child3;
 delete from parent;
-NOTICE:  trigger = parent_delete_trig, old table = (AAA,42), (BBB,42), (CCC,42)
+NOTICE:  trigger = parent_delete_trig, old table = (AAA,42), (BBB,42), (CCC,42), (DDD,42)
 drop table child1, child2, child3, parent;
 --
 -- Verify prohibition of row triggers with transition triggers on

src/test/regress/sql/triggers.sql

@@ -1661,6 +1661,13 @@ BBB	42
 CCC	42
 \.
 
+-- same behavior for copy if there is an index (interesting because rows are
+-- captured by a different code path in copy.c if there are indexes)
+create index on parent(b);
+copy parent (a, b) from stdin;
+DDD	42
+\.
+
 -- DML affecting parent sees tuples collected from children even if
 -- there is no transition table trigger on the children
 drop trigger child1_insert_trig on child1;