Added more examples and pgsql reader

examples/pgsql_meta_upgrade/get_table_fields.sql

@@ -0,0 +1,90 @@
+--select * from dropall('meta.get_table_fields');
+CREATE OR REPLACE FUNCTION meta.get_table_fields(
+  p_schema_name text
+ ,p_table_name text
+)
+RETURNS JSONB
+LANGUAGE plpgsql STABLE
+  cost 10
+SECURITY DEFINER
+AS
+$$
+DECLARE
+  a_primary_keys citext[];
+  a_foreign_keys citext[];
+BEGIN
+
+  SELECT array_agg(kcu.column_name::citext)
+  FROM information_schema.table_constraints tc
+  JOIN information_schema.key_column_usage kcu
+         ON tc.constraint_name = kcu.constraint_name
+           AND tc.table_schema = kcu.table_schema
+  WHERE
+      tc.constraint_type = 'PRIMARY KEY'
+  AND tc.table_schema = p_schema_name::citext
+  AND tc.table_name = p_table_name::citext
+  INTO a_primary_keys
+  ;
+
+  SELECT array_agg(kcu.column_name::citext)
+  FROM information_schema.table_constraints tc
+  JOIN information_schema.key_column_usage kcu
+         ON tc.constraint_name = kcu.constraint_name
+           AND tc.table_schema = kcu.table_schema
+  WHERE
+      tc.constraint_type = 'FOREIGN KEY'
+  AND tc.table_schema = p_schema_name::citext
+  AND tc.table_name = p_table_name::citext
+  INTO a_foreign_keys
+  ;
+
+  return (
+    SELECT jsonb_object_agg(col.column_name::citext
+             , jsonb_build_object(
+                                'type', case
+                                          when col.data_type::citext = 'USER-DEFINED' then col.udt_name::citext
+                                          else col.data_type::citext
+                                        end
+                              , 'primary_key', case when col.column_name = any (a_primary_keys) then true else false end
+                              , 'foreign_key', case when col.column_name = any (a_foreign_keys) then true else false end
+                              ,'relation', (
+                                  select to_jsonb(r)
+                                  from (
+                                    SELECT DISTINCT
+                                           c.table_schema AS parent_schema
+                                      ,    c.table_name AS parent_table
+                                      ,    cc.column_name AS parent_column
+                                      --,    kcu.column_name AS relation_column
+
+                                    FROM information_schema.table_constraints tc
+                                    JOIN information_schema.constraint_column_usage ccu
+                                           ON tc.constraint_name = ccu.constraint_name
+                                             AND tc.table_schema = ccu.table_schema
+                                    JOIN information_schema.key_column_usage kcu
+                                           ON tc.constraint_name = kcu.constraint_name
+                                             AND tc.table_schema = kcu.table_schema
+                                    JOIN information_schema.referential_constraints rc
+                                           ON tc.constraint_name = rc.constraint_name
+                                    JOIN information_schema.constraint_column_usage cc
+                                           ON rc.unique_constraint_name = cc.constraint_name
+                                    JOIN information_schema.constraint_table_usage c
+                                           ON rc.unique_constraint_name = c.constraint_name
+                                    WHERE
+                                        tc.constraint_type = 'FOREIGN KEY'
+                                    AND tc.table_schema = p_schema_name::citext
+                                    AND tc.table_name = p_table_name::citext
+                                    and kcu.column_name = col.column_name
+                                  ) r
+                              )
+               )
+           )
+    FROM information_schema.columns col
+    WHERE
+        col.table_schema = p_schema_name::citext
+    AND col.table_name = p_table_name::citext
+  );
+
+END;
+$$;
+
+--select meta.get_table_fields('core','masterprocess')