add database trigger to ensure indexers cannot miss any blocks

packages/fuel-indexer-database/postgres/migrations/20230913134030_add_ensure_block_height_consecutive_function.down.sql

@@ -0,0 +1 @@
+DROP FUNCTION IF EXISTS ensure_block_height_consecutive;

packages/fuel-indexer-database/postgres/migrations/20230913134030_add_ensure_block_height_consecutive_function.up.sql

@@ -0,0 +1,14 @@
+CREATE OR REPLACE FUNCTION ensure_block_height_consecutive()
+RETURNS TRIGGER AS $$
+DECLARE
+  block_height integer;
+BEGIN
+  EXECUTE format('SELECT MAX(block_height) FROM %I.%I', TG_TABLE_SCHEMA, TG_TABLE_NAME) INTO block_height;
+
+  IF NEW.block_height IS NOT NULL AND block_height IS NOT NULL AND NEW.block_height != block_height + 1 THEN
+    RAISE EXCEPTION '%.%: attempted to insert value with block_height = % while last indexed block_height = %. block_height values must be consecutive.', TG_TABLE_SCHEMA, TG_TABLE_NAME, NEW.block_height, block_height;
+  END IF;
+
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;

packages/fuel-indexer-schema/src/db/tables.rs

@@ -183,6 +183,15 @@ impl IndexerSchema {
 
         statements.extend(constraint_stmnts);
 
+        statements.push(format!(
+            "CREATE TRIGGER trigger_ensure_block_height_consecutive
+            BEFORE INSERT OR UPDATE ON {namespace}_{identifier}.indexmetadataentity
+            FOR EACH ROW
+            EXECUTE FUNCTION ensure_block_height_consecutive();",
+            namespace = self.namespace,
+            identifier = self.identifier
+        ));
+
         for stmnt in statements.iter() {
             queries::execute_query(conn, stmnt.to_owned()).await?;
         }