Add support for user functions (#608)

* Add initial support for functions
* Show functions definitions
* Fix client tests
* Fix schema objects search
* Perform partial matching for functions
* Add function test
* Make sure to close client connections so that database could be dropped in tests
* Fix lint
* Allow to copy the view/functions definitions
* Nits

pkg/statements/sql/function.sql

@@ -0,0 +1,7 @@
+SELECT
+  p.*,
+  pg_get_functiondef(oid) AS functiondef
+FROM
+  pg_catalog.pg_proc p
+WHERE
+  oid = $1::oid

pkg/statements/sql/objects.sql

@@ -1,25 +1,46 @@
-SELECT
-  n.nspname AS schema,
-  c.relname AS name,
-  CASE c.relkind
-    WHEN 'r' THEN 'table'
-    WHEN 'v' THEN 'view'
-    WHEN 'm' THEN 'materialized_view'
-    WHEN 'i' THEN 'index'
-    WHEN 'S' THEN 'sequence'
-    WHEN 's' THEN 'special'
-    WHEN 'f' THEN 'foreign_table'
-  END AS type,
-  pg_catalog.pg_get_userbyid(c.relowner) AS owner,
-  pg_catalog.obj_description(c.oid) AS comment
-FROM
-  pg_catalog.pg_class c
-LEFT JOIN
-  pg_catalog.pg_namespace n ON n.oid = c.relnamespace
-WHERE
-  c.relkind IN ('r','v','m','S','s','')
-  AND n.nspname !~ '^pg_toast'
-  AND n.nspname NOT IN ('information_schema', 'pg_catalog')
-  AND has_schema_privilege(n.nspname, 'USAGE')
-ORDER BY
-  1, 2
+WITH all_objects AS (
+  SELECT
+    c.oid,
+    n.nspname AS schema,
+    c.relname AS name,
+    CASE c.relkind
+      WHEN 'r' THEN 'table'
+      WHEN 'v' THEN 'view'
+      WHEN 'm' THEN 'materialized_view'
+      WHEN 'i' THEN 'index'
+      WHEN 'S' THEN 'sequence'
+      WHEN 's' THEN 'special'
+      WHEN 'f' THEN 'foreign_table'
+    END AS type,
+    pg_catalog.pg_get_userbyid(c.relowner) AS owner,
+    pg_catalog.obj_description(c.oid) AS comment
+  FROM
+    pg_catalog.pg_class c
+  LEFT JOIN
+    pg_catalog.pg_namespace n ON n.oid = c.relnamespace
+  WHERE
+    c.relkind IN ('r','v','m','S','s','')
+    AND n.nspname !~ '^pg_toast'
+    AND n.nspname NOT IN ('information_schema', 'pg_catalog')
+    AND has_schema_privilege(n.nspname, 'USAGE')
+
+  UNION
+
+  SELECT
+    p.oid,
+    n.nspname AS schema,
+    p.proname AS name,
+    'function' AS function,
+    pg_catalog.pg_get_userbyid(p.proowner) AS owner,
+    NULL AS comment
+  FROM
+    pg_catalog.pg_namespace n
+  JOIN
+    pg_catalog.pg_proc p ON p.pronamespace = n.oid
+  WHERE
+    n.nspname !~ '^pg_toast'
+    AND n.nspname NOT IN ('information_schema', 'pg_catalog')
+    AND p.prokind = 'f'
+)
+SELECT * FROM all_objects
+ORDER BY 1, 2