MySQL Slow Query Log Analysis for 1C-Bitrix: Speed Up Your Site

You launch a site on 1C-Bitrix, but pages load in 5–10 seconds. Clients leave, managers complain. You checked hosting and caching, but the cause remains unclear. The slow query log — a MySQL log of slow queries — reveals the true culprits. Without it, you're guessing, and every second of delay costs
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MySQL Slow Query Log Analysis for 1C-Bitrix: Speed Up Your Site
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You launch a site on 1C-Bitrix, but pages load in 5–10 seconds. Clients leave, managers complain. You checked hosting and caching, but the cause remains unclear. The slow query log — a MySQL log of slow queries — reveals the true culprits. Without it, you're guessing, and every second of delay costs money: conversion drops, ad budget burns. We help analyze the log, find the heaviest queries, and optimize them. In 2–3 days, you'll receive a report and ready-made solutions, and the speed savings will pay for the investment in a week.

In this article, we'll cover how to enable the slow log, which utilities to use for analysis (mysqldumpslow, pt-query-digest), and which typical queries slow down Bitrix. Most importantly, we'll show a real case where a simple index creation dropped query time from 3 seconds to 10 milliseconds. If you want to solve the problem quickly, contact us: we'll conduct an audit in 1 day.

Why slow queries are the main problem for Bitrix

The main cause is non-optimal database queries. Bitrix heavily uses information blocks, properties, and trade offers. With a large number of elements without proper indexes, every query becomes a full table scan. The slow query log catches such queries. Here are three typical problem groups:

  • Queries to b_iblock_element without an index on IBLOCK_ID and SORT.
  • LIKE with a leading wildcard during filtering.
  • COUNT(*) on b_sale_order with millions of records. Our experience: in 80% of cases, adding 2–3 composite indexes eliminates 90% of slow queries. This saves budget for expensive server upgrades.

How to enable and configure the slow query log

In my.cnf (or my.ini on Windows):

[mysqld] slow_query_log = 1 slow_query_log_file = /var/log/mysql/slow.log long_query_time = 0.5 log_queries_not_using_indexes = 1 min_examined_row_limit = 100

long_query_time = 0.5 — queries longer than 500 ms. For active diagnostics, set it to 0.1 or even 0. log_queries_not_using_indexes = 1 — catches queries without indexes regardless of time. min_examined_row_limit = 100 — do not log fast queries on small tables.

You can enable it dynamically without restarting MySQL:

SET GLOBAL slow_query_log = 'ON'; SET GLOBAL long_query_time = 0.5; SET GLOBAL log_queries_not_using_indexes = 1;

You can read more about the slow log on Wikipedia.

How to find slow queries

Reading the raw log is inconvenient. Use aggregation utilities: mysqldumpslow — built into MySQL:

mysqldumpslow -s t -t 10 /var/log/mysql/slow.log

-s t — sort by total time, -t 10 — top 10 queries. Shows query pattern and total/average time.

pt-query-digest (Percona Toolkit) — significantly more informative: shows execution time percentiles, number of unique queries, server load.

Utility Speed Informativeness Additional features
mysqldumpslow Fast Basic None
pt-query-digest Slower Detailed (percentiles, profiles) Flexible filtering, reports

pt-query-digest shows not just average time but also distribution — 3 times more detailed than mysqldumpslow.

Typical slow queries in Bitrix

Problem Example SQL Solution
Full catalog scan SELECT * FROM b_iblock_element WHERE IBLOCK_ID=5 ORDER BY SORT Composite index (IBLOCK_ID, SORT)
LIKE without index SELECT * FROM b_iblock_element_property WHERE VALUE LIKE '%search%' FULLTEXT index or MATCH AGAINST
COUNT(*) on orders SELECT COUNT(*) FROM b_sale_order WHERE STATUS='N' Index on STATUS or partitioning

Adding an index in the first case reduces execution time from 3 seconds to 0.01 seconds — 300 times faster.

Case study: how we accelerated a catalog 20 times

A client — an online store with 50,000 products. Catalog pages loaded in 6–8 seconds. The slow query log revealed a query to b_iblock_element_property with LIKE '%text%'. We created a FULLTEXT index and rewrote the query to use MATCH AGAINST. Execution time dropped from 2.3 s to 0.12 s. Overall page load time decreased to 1.2 seconds. MySQL FULLTEXT

Want the same? Get a consultation — we'll evaluate your case in an hour.

What's included in the work

  • Analysis of the slow query log for 7 days (or a specified period).
  • Identification of the top-10 slow queries.
  • EXPLAIN and index recommendations.
  • Implementation of optimizations (creating/altering indexes, query refactoring).
  • Report with before/after metrics.

Work process

  1. Enable slow log on your server (remotely).
  2. Collect log over a representative period (usually 1–2 days).
  3. Analyze using pt-query-digest.
  4. Deliver a report with priorities.
  5. Agree and implement changes.
  6. Re-measure to confirm improvement.

Timeline: 1 to 5 days depending on complexity.

Why trust us?

  • 7+ years of experience with Bitrix.
  • 300+ successful projects.
  • Certified 1C-Bitrix specialists.
  • Work under contract with a guarantee of results.

Ready to fix the slowdown? Contact us — we'll evaluate your project for free and propose a solution within 1 day.

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