From 0d7621be564fb27d834158d08e1471f572fc38b7 Mon Sep 17 00:00:00 2001
From: Fridrik Asmundsson <fridrik01@gmail.com>
Date: Tue, 11 Jul 2023 09:10:16 +0000
Subject: [PATCH] Add tmp indices to events table while performing migration to
 V2

After the migration we also perform db administration on the
events DB to reduce its file size on disk.
---
 chain/events/filter/index.go | 43 +++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/chain/events/filter/index.go b/chain/events/filter/index.go
index 27aec481f..bacba60d7 100644
--- a/chain/events/filter/index.go
+++ b/chain/events/filter/index.go
@@ -128,6 +128,16 @@ func (ei *EventIndex) migrateToVersion2(ctx context.Context, chainStore *store.C
 	// rollback the transaction (a no-op if the transaction was already committed)
 	defer tx.Rollback() //nolint:errcheck
 
+	// create some temporary indices to help speed up the migration
+	_, err = tx.Exec("CREATE INDEX IF NOT EXISTS tmp_height_tipset_key_cid ON event (height,tipset_key_cid)")
+	if err != nil {
+		return xerrors.Errorf("create index tmp_height_tipset_key_cid: %w", err)
+	}
+	_, err = tx.Exec("CREATE INDEX IF NOT EXISTS tmp_tipset_key_cid ON event (tipset_key_cid)")
+	if err != nil {
+		return xerrors.Errorf("create index tmp_tipset_key_cid: %w", err)
+	}
+
 	stmtDeleteOffChainEvent, err := tx.Prepare("DELETE FROM event WHERE tipset_key_cid!=? and height=?")
 	if err != nil {
 		return xerrors.Errorf("prepare stmtDeleteOffChainEvent: %w", err)
@@ -158,12 +168,16 @@ func (ei *EventIndex) migrateToVersion2(ctx context.Context, chainStore *store.C
 	currTs := chainStore.GetHeaviestTipSet()
 
 	for int64(currTs.Height()) >= minHeight.Int64 {
+		if currTs.Height()%1000 == 0 {
+			log.Infof("Migrating height %d (remaining %d)", currTs.Height(), int64(currTs.Height())-minHeight.Int64)
+		}
+
 		tsKey := currTs.Parents()
 		currTs, err = chainStore.GetTipSetFromKey(ctx, tsKey)
 		if err != nil {
 			return xerrors.Errorf("get tipset from key: %w", err)
 		}
-		log.Debugf("Migrating height %d\n", currTs.Height())
+		log.Debugf("Migrating height %d", currTs.Height())
 
 		tsKeyCid, err := currTs.Key().Cid()
 		if err != nil {
@@ -190,7 +204,7 @@ func (ei *EventIndex) migrateToVersion2(ctx context.Context, chainStore *store.C
 		if !eventId.Valid {
 			continue
 		}
-		log.Debugf("Deleting all events with id < %d at height %d\n", eventId.Int64, currTs.Height())
+		log.Debugf("Deleting all events with id < %d at height %d", eventId.Int64, currTs.Height())
 
 		res, err := stmtDeleteEvent.Exec(tsKeyCid.Bytes(), eventId.Int64)
 		if err != nil {
@@ -201,7 +215,7 @@ func (ei *EventIndex) migrateToVersion2(ctx context.Context, chainStore *store.C
 		if err != nil {
 			return xerrors.Errorf("rows affected: %w", err)
 		}
-		log.Debugf("deleted %d events from tipset %s\n", nrRowsAffected, tsKeyCid.String())
+		log.Debugf("deleted %d events from tipset %s", nrRowsAffected, tsKeyCid.String())
 	}
 
 	// delete all entries that have an event_id that doesn't exist (since we don't have a foreign
@@ -217,11 +231,34 @@ func (ei *EventIndex) migrateToVersion2(ctx context.Context, chainStore *store.C
 	}
 	log.Infof("cleaned up %d entries that had deleted events\n", nrRowsAffected)
 
+	// drop the temporary indices after the migration
+	_, err = tx.Exec("DROP INDEX IF EXISTS tmp_tipset_key_cid")
+	if err != nil {
+		return xerrors.Errorf("create index tmp_tipset_key_cid: %w", err)
+	}
+	_, err = tx.Exec("DROP INDEX IF EXISTS tmp_height_tipset_key_cid")
+	if err != nil {
+		return xerrors.Errorf("drop index tmp_height_tipset_key_cid: %w", err)
+	}
+
 	err = tx.Commit()
 	if err != nil {
 		return xerrors.Errorf("commit transaction: %w", err)
 	}
 
+	// during the migration, we have likely increased the WAL size a lot, so lets do some
+	// simple DB administration to free up space (VACUUM followed by truncating the WAL file)
+	// as this would be a good time to do it when no other writes are happening
+	log.Infof("Performing DB vacuum and wal checkpointing to free up space after the migration")
+	_, err = ei.db.Exec("VACUUM")
+	if err != nil {
+		log.Warnf("error vacuuming database: %s", err)
+	}
+	_, err = ei.db.Exec("PRAGMA wal_checkpoint(TRUNCATE)")
+	if err != nil {
+		log.Warnf("error checkpointing wal: %s", err)
+	}
+
 	log.Infof("Successfully migrated events to version 2 in %s", time.Since(now))
 
 	return nil