Rearrange core regression tests to reduce cross-script dependencies.

The idea behind this patch is to make it possible to run individual
test scripts without running the entire core test suite.  Making all
the scripts completely independent would involve a massive rewrite,
and would probably be worse for coverage of things like concurrent DDL.
So this patch just does what seems practical with limited changes.

The net effect is that any test script can be run after running
limited earlier dependencies:
* all scripts depend on test_setup
* many scripts depend on create_index
* other dependencies are few in number, and are documented in
  the parallel_schedule file.

To accomplish this, I chose a small number of commonly-used tables
and moved their creation and filling into test_setup.  Later scripts
are expected not to modify these tables' data contents, for fear of
affecting other scripts' results.  Also, our former habit of declaring
all C functions in one place is now gone in favor of declaring them
where they're used, if that's just one script, or in test_setup if
necessary.

There's more that could be done to remove some of the remaining
inter-script dependencies, but significantly more-invasive changes
would be needed, and at least for now it doesn't seem worth it.

Discussion: https://postgr.es/m/1114748.1640383217@sss.pgh.pa.us

1 files changed, 16 insertions, 0 deletions

diff --git a/src/test/regress/sql/misc_functions.sql b/src/test/regress/sql/misc_functions.sql
index cfaba456e15..3db3f8bade2 100644
--- a/src/test/regress/sql/misc_functions.sql
+++ b/src/test/regress/sql/misc_functions.sql
@@ -1,3 +1,9 @@
+-- directory paths and dlsuffix are passed to us in environment variables
+\getenv libdir PG_LIBDIR
+\getenv dlsuffix PG_DLSUFFIX
+
+\set regresslib :libdir '/regress' :dlsuffix
+
 --
 -- num_nulls()
 --
@@ -34,6 +40,11 @@ SELECT num_nulls();
 -- canonicalize_path()
 --
 
+CREATE FUNCTION test_canonicalize_path(text)
+   RETURNS text
+   AS :'regresslib'
+   LANGUAGE C STRICT IMMUTABLE;
+
 SELECT test_canonicalize_path('/');
 SELECT test_canonicalize_path('/./abc/def/');
 SELECT test_canonicalize_path('/./../abc/def');
@@ -156,6 +167,11 @@ SELECT * FROM tenk1 a JOIN tenk1 b ON a.unique1 = b.unique1
 WHERE my_int_eq(a.unique2, 42);
 
 -- With support function that knows it's int4eq, we get a different plan
+CREATE FUNCTION test_support_func(internal)
+    RETURNS internal
+    AS :'regresslib', 'test_support_func'
+    LANGUAGE C STRICT;
+
 ALTER FUNCTION my_int_eq(int, int) SUPPORT test_support_func;
 
 EXPLAIN (COSTS OFF)