Backup batches on fork id update (#128)

* Add batch backup

* Unit test

* Update the diff

* Apply feedback

Co-authored-by: Goran Rojovic <[email protected]>

---------

Co-authored-by: bros <[email protected]>
Co-authored-by: Goran Rojovic <[email protected]>

db/migrations/state/validium-001.sql

@@ -0,0 +1,32 @@
+-- +migrate Up
+
+CREATE TABLE IF NOT EXISTS state.batch_data_backup
+(
+    batch_num  BIGINT,
+    data       BYTEA,
+    created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    PRIMARY KEY (batch_num, created_at)
+);
+
+-- +migrate StatementBegin
+CREATE OR REPLACE FUNCTION backup_batch() RETURNS trigger AS $$
+    BEGIN
+        INSERT  INTO state.batch_data_backup (batch_num,     data) 
+                VALUES                       (OLD.batch_num, OLD.raw_txs_data)
+                ON CONFLICT (batch_num, created_at) DO UPDATE SET
+                    data = EXCLUDED.data;
+        RETURN OLD;
+    END;
+$$
+LANGUAGE plpgsql;
+-- +migrate StatementEnd
+
+CREATE TRIGGER backup_batch
+   BEFORE DELETE ON state.batch FOR EACH ROW
+   EXECUTE PROCEDURE backup_batch();
+
+-- +migrate Down
+
+DROP TRIGGER IF EXISTS backup_batch ON state.batch;
+DROP FUNCTION IF EXISTS backup_batch();
+DROP TABLE IF EXISTS state.batch_data_backup;