Add a new system view, pg_prepared_statements, that can be used to

access information about the prepared statements that are available
in the current session. Original patch from Joachim Wieland, various
improvements by Neil Conway.

The "statement" column of the view contains the literal query string
sent by the client, without any rewriting or pretty printing. This
means that prepared statements created via SQL will be prefixed with
"PREPARE ... AS ", whereas those prepared via the FE/BE protocol will
not. That is unfortunate, but discussion on -patches did not yield an
efficient way to improve this, and there is some merit in returning
exactly what the client sent to the backend.

Catalog version bumped, regression tests updated.

1 files changed, 22 insertions, 2 deletions

diff --git a/src/test/regress/sql/prepare.sql b/src/test/regress/sql/prepare.sql
index fc6924307d..95db2a0910 100644
--- a/src/test/regress/sql/prepare.sql
+++ b/src/test/regress/sql/prepare.sql
@@ -1,8 +1,14 @@
--- Regression tests for prepareable statements
+-- Regression tests for prepareable statements. We query the content
+-- of the pg_prepared_statements view as prepared statements are
+-- created and removed.
 
-PREPARE q1 AS SELECT 1;
+SELECT name, statement, parameter_types FROM pg_prepared_statements;
+
+PREPARE q1 AS SELECT 1 AS a;
 EXECUTE q1;
 
+SELECT name, statement, parameter_types FROM pg_prepared_statements;
+
 -- should fail
 PREPARE q1 AS SELECT 2;
 
@@ -11,19 +17,33 @@ DEALLOCATE q1;
 PREPARE q1 AS SELECT 2;
 EXECUTE q1;
 
+PREPARE q2 AS SELECT 2 AS b;
+SELECT name, statement, parameter_types FROM pg_prepared_statements;
+
 -- sql92 syntax
 DEALLOCATE PREPARE q1;
 
+SELECT name, statement, parameter_types FROM pg_prepared_statements;
+
+DEALLOCATE PREPARE q2;
+-- the view should return the empty set again
+SELECT name, statement, parameter_types FROM pg_prepared_statements;
+
 -- parameterized queries
 PREPARE q2(text) AS
 	SELECT datname, datistemplate, datallowconn
 	FROM pg_database WHERE datname = $1;
+
+SELECT name, statement, parameter_types FROM pg_prepared_statements;
+
 EXECUTE q2('regression');
 
 PREPARE q3(text, int, float, boolean, oid, smallint) AS
 	SELECT * FROM tenk1 WHERE string4 = $1 AND (four = $2 OR
 	ten = $3::bigint OR true = $4 OR oid = $5 OR odd = $6::int);
 
+SELECT name, statement, parameter_types FROM pg_prepared_statements;
+
 EXECUTE q3('AAAAxx', 5::smallint, 10.5::float, false, 500::oid, 4::bigint);
 
 -- too few params