Re: invalid memory alloc request size error with commit 4b93f579

I wrote:
> I wonder whether it is worth creating a C trigger function
> (probably in regress.c) specifically to exercise this situation.

Actually, that doesn't seem too bad at all.  I propose applying
and back-patching the attached.

BTW, I noticed while doing this that the adjacent "funny_dup17"
trigger is dead code, and has been since commit 1547ee01 of
1999-09-29.  I'm inclined to rip it out, because anyone looking
at regress.c would naturally assume that anything in there is
being exercised.

            regards, tom lane

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index fffc009..fbd176b 100644
*** a/src/backend/commands/trigger.c
--- b/src/backend/commands/trigger.c
*************** ExecBRUpdateTriggers(EState *estate, EPQ
*** 2815,2821 ****
              return NULL;        /* "do nothing" */
          }
      }
!     if (trigtuple != fdw_trigtuple)
          heap_freetuple(trigtuple);

      if (newtuple != slottuple)
--- 2815,2821 ----
              return NULL;        /* "do nothing" */
          }
      }
!     if (trigtuple != fdw_trigtuple && trigtuple != newtuple)
          heap_freetuple(trigtuple);

      if (newtuple != slottuple)
diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out
index ce8fa21..4771069 100644
*** a/src/test/regress/expected/triggers.out
--- b/src/test/regress/expected/triggers.out
*************** DROP TABLE fkeys2;
*** 153,158 ****
--- 153,184 ----
  -- select count(*) from dup17 where x = 13;
  --
  -- DROP TABLE dup17;
+ -- Check behavior when trigger returns unmodified trigtuple
+ create table trigtest (f1 int, f2 text);
+ create trigger trigger_return_old
+     before insert or delete or update on trigtest
+     for each row execute procedure trigger_return_old();
+ insert into trigtest values(1, 'foo');
+ select * from trigtest;
+  f1 | f2
+ ----+-----
+   1 | foo
+ (1 row)
+
+ update trigtest set f2 = f2 || 'bar';
+ select * from trigtest;
+  f1 | f2
+ ----+-----
+   1 | foo
+ (1 row)
+
+ delete from trigtest;
+ select * from trigtest;
+  f1 | f2
+ ----+----
+ (0 rows)
+
+ drop table trigtest;
  create sequence ttdummy_seq increment 10 start 0 minvalue 0;
  create table tttest (
      price_id    int4,
diff --git a/src/test/regress/input/create_function_1.source b/src/test/regress/input/create_function_1.source
index cde78eb..6b6bcd8 100644
*** a/src/test/regress/input/create_function_1.source
--- b/src/test/regress/input/create_function_1.source
*************** CREATE FUNCTION funny_dup17 ()
*** 42,47 ****
--- 42,52 ----
          AS '@libdir@/regress@DLSUFFIX@'
          LANGUAGE C;

+ CREATE FUNCTION trigger_return_old ()
+         RETURNS trigger
+         AS '@libdir@/regress@DLSUFFIX@'
+         LANGUAGE C;
+
  CREATE FUNCTION ttdummy ()
          RETURNS trigger
          AS '@libdir@/regress@DLSUFFIX@'
diff --git a/src/test/regress/output/create_function_1.source b/src/test/regress/output/create_function_1.source
index ab601be..9154b4a 100644
*** a/src/test/regress/output/create_function_1.source
--- b/src/test/regress/output/create_function_1.source
*************** CREATE FUNCTION funny_dup17 ()
*** 39,44 ****
--- 39,48 ----
          RETURNS trigger
          AS '@libdir@/regress@DLSUFFIX@'
          LANGUAGE C;
+ CREATE FUNCTION trigger_return_old ()
+         RETURNS trigger
+         AS '@libdir@/regress@DLSUFFIX@'
+         LANGUAGE C;
  CREATE FUNCTION ttdummy ()
          RETURNS trigger
          AS '@libdir@/regress@DLSUFFIX@'
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index 13e7207..521b181 100644
*** a/src/test/regress/regress.c
--- b/src/test/regress/regress.c
*************** funny_dup17(PG_FUNCTION_ARGS)
*** 444,449 ****
--- 444,465 ----
      return PointerGetDatum(tuple);
  }

+ PG_FUNCTION_INFO_V1(trigger_return_old);
+
+ Datum
+ trigger_return_old(PG_FUNCTION_ARGS)
+ {
+     TriggerData *trigdata = (TriggerData *) fcinfo->context;
+     HeapTuple    tuple;
+
+     if (!CALLED_AS_TRIGGER(fcinfo))
+         elog(ERROR, "trigger_return_old: not fired by trigger manager");
+
+     tuple = trigdata->tg_trigtuple;
+
+     return PointerGetDatum(tuple);
+ }
+
  #define TTDUMMY_INFINITY    999999

  static SPIPlanPtr splan = NULL;
diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql
index ae8349c..2bad469 100644
*** a/src/test/regress/sql/triggers.sql
--- b/src/test/regress/sql/triggers.sql
*************** DROP TABLE fkeys2;
*** 138,143 ****
--- 138,159 ----
  --
  -- DROP TABLE dup17;

+ -- Check behavior when trigger returns unmodified trigtuple
+ create table trigtest (f1 int, f2 text);
+
+ create trigger trigger_return_old
+     before insert or delete or update on trigtest
+     for each row execute procedure trigger_return_old();
+
+ insert into trigtest values(1, 'foo');
+ select * from trigtest;
+ update trigtest set f2 = f2 || 'bar';
+ select * from trigtest;
+ delete from trigtest;
+ select * from trigtest;
+
+ drop table trigtest;
+
  create sequence ttdummy_seq increment 10 start 0 minvalue 0;

  create table tttest (