[POC] Improving selectivity estimates for system views

contrib/babelfishpg_tsql/Makefile

@@ -79,6 +79,7 @@ OBJS += src/fts.o
 OBJS += src/fts_parser.o
 OBJS += src/pltsql_partition.o
 OBJS += src/bbf_parallel_query.o
+OBJS += src/namespace_support.o
 OBJS += src/temp_table.o
 
 export ANTLR4_JAVA_BIN=java

contrib/babelfishpg_tsql/sql/babelfishpg_tsql.in

@@ -18,6 +18,7 @@ SELECT set_config('search_path', 'sys, '||current_setting('search_path'), false)
 #include "babelfish_partitions.sql"
 #include "linked_servers_tsql.sql"
 #include "ownership.sql"
+#include "namespace_support.sql"
 #include "sys_views.sql"
 #include "information_schema_tsql.sql"
 #include "sys_procedures.sql"

contrib/babelfishpg_tsql/sql/namespace_support.sql

@@ -0,0 +1,41 @@
+-- SQL declarations for is_babelfish_namespace with prosupport
+-- Run this after building and installing the extension
+
+-- Create the support function first
+CREATE OR REPLACE FUNCTION sys.is_babelfish_namespace_support(internal)
+RETURNS internal
+AS 'babelfishpg_tsql', 'is_babelfish_namespace_support'
+LANGUAGE C STRICT;
+
+-- Create the main function with SUPPORT clause
+CREATE OR REPLACE FUNCTION sys.is_babelfish_namespace(ns_oid oid)
+RETURNS boolean
+AS 'babelfishpg_tsql', 'is_babelfish_namespace'
+LANGUAGE C STABLE STRICT
+SUPPORT sys.is_babelfish_namespace_support;
+
+-- Privilege support function: provides accurate selectivity for has_*_privilege()
+CREATE OR REPLACE FUNCTION sys.has_privilege_support(internal)
+RETURNS internal
+AS 'babelfishpg_tsql', 'has_privilege_support'
+LANGUAGE C STRICT;
+
+-- Attach to built-in privilege functions used in system views
+UPDATE pg_catalog.pg_proc SET prosupport = 'sys.has_privilege_support'::regproc
+WHERE proname = 'has_table_privilege'
+  AND pronargs = 2
+  AND proargtypes[0] = 'oid'::regtype
+  AND proargtypes[1] = 'text'::regtype;
+
+UPDATE pg_catalog.pg_proc SET prosupport = 'sys.has_privilege_support'::regproc
+WHERE proname = 'has_function_privilege'
+  AND pronargs = 2
+  AND proargtypes[0] = 'oid'::regtype
+  AND proargtypes[1] = 'text'::regtype;
+
+UPDATE pg_catalog.pg_proc SET prosupport = 'sys.has_privilege_support'::regproc
+WHERE proname = 'has_column_privilege'
+  AND pronargs = 3
+  AND proargtypes[0] = 'oid'::regtype
+  AND proargtypes[1] = 'text'::regtype
+  AND proargtypes[2] = 'text'::regtype;