simplify postgres migration scripts

migrations/message_store_postgres/content_script_version_6.nim

@@ -1,85 +1,15 @@
 const ContentScriptVersion_6* =
   """
--- Rename old table
-ALTER TABLE IF EXISTS MESSAGES
-RENAME TO OLD_MESSAGES;
+-- we can drop the timestamp column because this data is also kept in the storedAt column
+ALTER TABLE messages DROP COLUMN timestamp;
 
--- Remove old message index
-ALTER TABLE IF EXISTS OLD_MESSAGES
-DROP CONSTRAINT MESSAGEINDEX;
+-- drop unused column
+ALTER TABLE messages DROP COLUMN id;
 
--- Create new empty table
-CREATE TABLE IF NOT EXISTS NEW_MESSAGES (
-	MESSAGEHASH VARCHAR NOT NULL,
-	PUBSUBTOPIC VARCHAR NOT NULL,
-	CONTENTTOPIC VARCHAR NOT NULL,
-	PAYLOAD VARCHAR,
-	VERSION INTEGER NOT NULL,
-	TIMESTAMP BIGINT NOT NULL,
-	META VARCHAR,
-	CONSTRAINT MESSAGEINDEX PRIMARY KEY (TIMESTAMP, MESSAGEHASH)
-)
-PARTITION BY
-	RANGE (TIMESTAMP);
-
-DO $$
-DECLARE
-	partition_name TEXT;
-	partition_count numeric;
-	min_timestamp numeric;
-	max_timestamp numeric;
-BEGIN
-    FOR partition_name in 
-		(SELECT child.relname AS partition_name FROM pg_inherits
-		JOIN pg_class parent            ON pg_inherits.inhparent = parent.oid
-		JOIN pg_class child             ON pg_inherits.inhrelid   = child.oid
-		JOIN pg_namespace nmsp_parent   ON nmsp_parent.oid  = parent.relnamespace
-		JOIN pg_namespace nmsp_child    ON nmsp_child.oid   = child.relnamespace
-		WHERE parent.relname='old_messages'
-		ORDER BY partition_name ASC)
-    LOOP
-
-	-- Get the number of rows of this partition
-	EXECUTE format('SELECT COUNT(1) FROM %I', partition_name) INTO partition_count;
-
-	IF partition_count > 0 THEN
-
-	-- Get the smallest timestamp of this partition
-	EXECUTE format('SELECT MIN(timestamp) FROM %I', partition_name) INTO min_timestamp;
-
-	-- Get the largest timestamp of this partition
-	EXECUTE format('SELECT MAX(timestamp) FROM %I', partition_name) INTO max_timestamp;
-
-	-- Rename old partition
-	EXECUTE format('ALTER TABLE %I RENAME TO old_%I', partition_name, partition_name);
-
-	-- Create new partition with the same name and bounds
-	EXECUTE format('CREATE TABLE %I PARTITION OF new_messages FOR VALUES FROM (%L) TO (%L)', partition_name, min_timestamp, max_timestamp + 1);
-	
-	-- Insert partition rows into new table
-	EXECUTE format('INSERT INTO %I (messageHash, pubsubTopic, contentTopic, payload, version, timestamp, meta, id, storedAt)
-		SELECT messageHash, pubsubTopic, contentTopic, payload, version, timestamp, meta, id, storedAt
-		FROM old_%I', partition_name, partition_name);
-
-	-- Drop old partition.
-	EXECUTE format('DROP TABLE old_%I', partition_name);
-	
-	END IF;
-	
-	END LOOP;
-END $$;
-
--- Remove old table
-DROP TABLE IF EXISTS OLD_MESSAGES;
-
--- Rename new table
-ALTER TABLE IF EXISTS NEW_MESSAGES
-RENAME TO MESSAGES;
+-- from now on we are only interested in the message timestamp
+ALTER TABLE messages RENAME COLUMN storedAt TO timestamp;
 
 -- Update to new version 
-UPDATE VERSION
-SET
-	VERSION = 6
-WHERE
-	VERSION = 5;
+UPDATE version SET version = 6 WHERE version = 5;
+
 """