Draft: feat(engine): schema diff (#329)

Description

Schema difference in DLE:

• Generate schema difference between clone and its snapshot
• Add a new endpoint to DLE API that generates the schema difference - GET /clone/diff/[CLONE_ID]
• Add a new command to CLI that generates the schema difference - dblab clone schema-diff [CLONE_ID]
• Use a global configuration database name (or default if it is not set) when clone creates if the creation request does not specify it
• Build DLE image using multistage and without disabling CGO on alpine because of pg_query dependencies
• Create an independent CLI tool to compare DB schemas and generates its diff

Related issue

#329

Examples

Generated schema diff

CREATE UNIQUE INDEX title_idx ON films (title);

DROP INDEX title_idx;

ALTER TABLE distributors 
	ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5);

ALTER TABLE distributors 
	ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address);

ALTER TABLE pgbench_accounts
    ADD COLUMN test integer NOT NULL DEFAULT 0;

Optimized queries

CREATE UNIQUE INDEX CONCURRENTLY title_idx ON films USING btree (title);

DROP INDEX CONCURRENTLY title_idx;

BEGIN; ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5) NOT VALID; COMMIT;
BEGIN; ALTER TABLE distributors VALIDATE CONSTRAINT zipchk; COMMIT;

BEGIN; ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address) NOT VALID; COMMIT;
BEGIN; ALTER TABLE distributors VALIDATE CONSTRAINT distfk; COMMIT;

BEGIN; ALTER TABLE pgbench_accounts ADD COLUMN test int; COMMIT;
BEGIN; ALTER TABLE pgbench_accounts ALTER COLUMN test SET DEFAULT 0; COMMIT; 
DO $$ 
DECLARE 
  -- Choose your own batch size
  batch_size int := 1000; 
  min_id bigint; max_id bigint;
BEGIN
  -- Choose your own column as a unique identifier instead of "aid"
  SELECT min(aid), max(aid) INTO min_id, max_id FROM pgbench_accounts;
  FOR i IN min_id..max_id BY batch_size LOOP 
	UPDATE pgbench_accounts SET test = 0
	WHERE aid >= i AND aid < i+batch_size;
	COMMIT;            
  END LOOP;
END; $$;
BEGIN; ALTER pgbench_accounts ALTER COLUMN pgbench_accounts SET NOT NULL; COMMIT;

Checklist

• the MR description has been reviewed
• this MR does NOT have text changes OR there are text changes and they have been reviewed
• this MR does NOT have API/CLI changes OR there are API/CLI changes and they have been reviewed
• this MR does NOT have UI changes OR there are UI changes and they have been reviewed

Closes #329