Follow-on cleanup for the transition table patch.

Commit 59702716 added transition table support to PL/pgsql so that
SQL queries in trigger functions could access those transient
tables.  In order to provide the same level of support for PL/perl,
PL/python and PL/tcl, refactor the relevant code into a new
function SPI_register_trigger_data.  Call the new function in the
trigger handler of all four PLs, and document it as a public SPI
function so that authors of out-of-tree PLs can do the same.

Also get rid of a second QueryEnvironment object that was
maintained by PL/pgsql.  That was previously used to deal with
cursors, but the same approach wasn't appropriate for PLs that are
less tangled up with core code.  Instead, have SPI_cursor_open
install the connection's current QueryEnvironment, as already
happens for SPI_execute_plan.

While in the docs, remove the note that transition tables were only
supported in C and PL/pgSQL triggers, and correct some ommissions.

Thomas Munro with some work by Kevin Grittner (mostly docs)

3 files changed, 46 insertions, 0 deletions

diff --git a/src/pl/tcl/expected/pltcl_queries.out b/src/pl/tcl/expected/pltcl_queries.out
index 7300b315d6..5f50f46887 100644
--- a/src/pl/tcl/expected/pltcl_queries.out
+++ b/src/pl/tcl/expected/pltcl_queries.out
@@ -660,3 +660,24 @@ select tcl_eval($$
  
 (1 row)
 
+-- test transition table visibility
+create table transition_table_test (id int, name text);
+insert into transition_table_test values (1, 'a');
+create function transition_table_test_f() returns trigger language pltcl as
+$$
+  spi_exec -array C "SELECT id, name FROM old_table" {
+    elog INFO "old: $C(id) -> $C(name)"
+  }
+  spi_exec -array C "SELECT id, name FROM new_table" {
+    elog INFO "new: $C(id) -> $C(name)"
+  }
+  return OK
+$$;
+CREATE TRIGGER a_t AFTER UPDATE ON transition_table_test
+  REFERENCING OLD TABLE AS old_table NEW TABLE AS new_table
+  FOR EACH STATEMENT EXECUTE PROCEDURE transition_table_test_f();
+update transition_table_test set name = 'b';
+INFO:  old: 1 -> a
+INFO:  new: 1 -> b
+drop table transition_table_test;
+drop function transition_table_test_f();
diff --git a/src/pl/tcl/pltcl.c b/src/pl/tcl/pltcl.c
index b8fcf0673d..5a48e5d175 100644
--- a/src/pl/tcl/pltcl.c
+++ b/src/pl/tcl/pltcl.c
@@ -1039,6 +1039,7 @@ pltcl_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
 	const char *result;
 	int			result_Objc;
 	Tcl_Obj   **result_Objv;
+	int			rc PG_USED_FOR_ASSERTS_ONLY;
 
 	call_state->trigdata = trigdata;
 
@@ -1046,6 +1047,10 @@ pltcl_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
 	if (SPI_connect() != SPI_OK_CONNECT)
 		elog(ERROR, "could not connect to SPI manager");
 
+	/* Make transition tables visible to this SPI connection */
+	rc = SPI_register_trigger_data(trigdata);
+	Assert(rc >= 0);
+
 	/* Find or compile the function */
 	prodesc = compile_pltcl_function(fcinfo->flinfo->fn_oid,
 									 RelationGetRelid(trigdata->tg_relation),
diff --git a/src/pl/tcl/sql/pltcl_queries.sql b/src/pl/tcl/sql/pltcl_queries.sql
index 29ed616cd0..dabd8cd35f 100644
--- a/src/pl/tcl/sql/pltcl_queries.sql
+++ b/src/pl/tcl/sql/pltcl_queries.sql
@@ -216,3 +216,23 @@ select tcl_eval($$
   after 100 {set ::tcl_vwait 1}
   vwait ::tcl_vwait
   unset -nocomplain ::tcl_vwait$$);
+
+-- test transition table visibility
+create table transition_table_test (id int, name text);
+insert into transition_table_test values (1, 'a');
+create function transition_table_test_f() returns trigger language pltcl as
+$$
+  spi_exec -array C "SELECT id, name FROM old_table" {
+    elog INFO "old: $C(id) -> $C(name)"
+  }
+  spi_exec -array C "SELECT id, name FROM new_table" {
+    elog INFO "new: $C(id) -> $C(name)"
+  }
+  return OK
+$$;
+CREATE TRIGGER a_t AFTER UPDATE ON transition_table_test
+  REFERENCING OLD TABLE AS old_table NEW TABLE AS new_table
+  FOR EACH STATEMENT EXECUTE PROCEDURE transition_table_test_f();
+update transition_table_test set name = 'b';
+drop table transition_table_test;
+drop function transition_table_test_f();