From a3bd1f7650103e859f0f1fff7e2a305e16f2d597 Mon Sep 17 00:00:00 2001
From: Mateusz Sekara <mateusz.sekara@smartcontract.com>
Date: Wed, 14 Feb 2024 09:30:34 +0100
Subject: [PATCH] Improving deletes performance by limiting number of records
 to scan (#12007)

* Improving deletes performance by limiting number of records to scan

* Post review fixes - replacing direct latestBlock call with nested query
---
 core/chains/evm/logpoller/orm.go      | 18 ++++++++++++++----
 core/chains/evm/logpoller/orm_test.go |  2 +-
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/core/chains/evm/logpoller/orm.go b/core/chains/evm/logpoller/orm.go
index 663c56d10ed..1db8271ccb6 100644
--- a/core/chains/evm/logpoller/orm.go
+++ b/core/chains/evm/logpoller/orm.go
@@ -12,6 +12,7 @@ import (
 	"github.com/pkg/errors"
 
 	"github.com/smartcontractkit/chainlink-common/pkg/logger"
+
 	ubig "github.com/smartcontractkit/chainlink/v2/core/chains/evm/utils/big"
 	"github.com/smartcontractkit/chainlink/v2/core/services/pg"
 )
@@ -196,8 +197,6 @@ func (o *DbORM) DeleteBlocksBefore(end int64, qopts ...pg.QOpt) error {
 }
 
 func (o *DbORM) DeleteLogsAndBlocksAfter(start int64, qopts ...pg.QOpt) error {
-	// These deletes are bounded by reorg depth, so they are
-	// fast and should not slow down the log readers.
 	return o.q.WithOpts(qopts...).Transaction(func(tx pg.Queryer) error {
 		args, err := newQueryArgs(o.chainID).
 			withStartBlock(start).
@@ -207,13 +206,24 @@ func (o *DbORM) DeleteLogsAndBlocksAfter(start int64, qopts ...pg.QOpt) error {
 			return err
 		}
 
-		_, err = tx.NamedExec(`DELETE FROM evm.log_poller_blocks WHERE block_number >= :start_block AND evm_chain_id = :evm_chain_id`, args)
+		// Applying upper bound filter is critical for Postgres performance (especially for evm.logs table)
+		// because it allows the planner to properly estimate the number of rows to be scanned.
+		// If not applied, these queries can become very slow. After some critical number
+		// of logs, Postgres will try to scan all the logs in the index by block_number.
+		// Latency without upper bound filter can be orders of magnitude higher for large number of logs.
+		_, err = tx.NamedExec(`DELETE FROM evm.log_poller_blocks 
+       						WHERE evm_chain_id = :evm_chain_id
+       						AND block_number >= :start_block
+       						AND block_number <= (SELECT MAX(block_number) FROM evm.log_poller_blocks WHERE evm_chain_id = :evm_chain_id)`, args)
 		if err != nil {
 			o.lggr.Warnw("Unable to clear reorged blocks, retrying", "err", err)
 			return err
 		}
 
-		_, err = tx.NamedExec(`DELETE FROM evm.logs WHERE block_number >= :start_block AND evm_chain_id = :evm_chain_id`, args)
+		_, err = tx.NamedExec(`DELETE FROM evm.logs 
+       						WHERE evm_chain_id = :evm_chain_id 
+       						AND block_number >= :start_block
+       						AND block_number <= (SELECT MAX(block_number) FROM evm.logs WHERE evm_chain_id = :evm_chain_id)`, args)
 		if err != nil {
 			o.lggr.Warnw("Unable to clear reorged logs, retrying", "err", err)
 			return err
diff --git a/core/chains/evm/logpoller/orm_test.go b/core/chains/evm/logpoller/orm_test.go
index 0af62ebd547..bcaa6f72fa0 100644
--- a/core/chains/evm/logpoller/orm_test.go
+++ b/core/chains/evm/logpoller/orm_test.go
@@ -1435,7 +1435,7 @@ func TestInsertLogsInTx(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			// clean all logs and blocks between test cases
-			defer func() { _ = o.DeleteLogsAndBlocksAfter(0) }()
+			defer func() { _, _ = db.Exec("truncate evm.logs") }()
 
 			insertErr := o.InsertLogs(tt.logs)
 			logsFromDb, err := o.SelectLogs(0, math.MaxInt, address, event)