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 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.

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

Typical slow queries in Bitrix

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.

1C-Bitrix Module Development and Setup

The main trap of Bitrix is init.php. You add an OnBeforeIBlockElementUpdate handler there, then another one — a year later the file is 2000 lines, and on every hit all that code executes. We move business logic into full-fledged modules with D7 ORM, custom tables, and administrative interface. The module can be disabled, transferred to another project, covered with tests — none of that is possible with init.php. Our team has 10+ years of Bitrix experience, certified specialists, and a 6-month code guarantee. Request a consultation — we'll explain how to migrate legacy code to a modular architecture.

Why is init.php the worst place for business logic?

Init.php does not support class autoloading, lacks an isolated namespace, cannot be unit tested, and cannot be disabled without editing the file itself. Every handler written there runs on every request, even if not needed. In a module, you register handlers through EventManager, and they only execute when the event occurs. Performance difference: up to 3x with 10+ handlers.

Standard Modules: Typical Problems and Solutions

Information blocks. IBlock architecture is the first thing we review on any project. A classic mistake: one catalog infoblock with 80 properties, 30 of which are multiple. The b_iblock_element_property table swells to millions of rows, and CIBlockElement::GetList with filtering on three properties does a full scan. We move reference data to Highload-blocks, eliminate multiple properties where possible, and design the structure for 5x growth.

e-Store (sale). Cart business rules are a separate story. We set discount priorities to prevent two campaigns from giving 60% instead of 30%, connect payment handlers, and write custom validation via OnSaleOrderBeforeSaved.

Search. The built-in search module with morphology works up to 10–15 thousand elements. Beyond that — Elasticsearch. We configure it via the Bitrix search module API, indexing through CSearchFullText or custom indexers.

Highload-blocks for dictionaries, logs, user data — instead of bloated IBlocks. Direct queries via Bitrix\Highloadblock\HighloadBlockTable, custom tables instead of the EAV structure of standard infoblocks. A million records — no degradation.

Mail events. Configuration is not just templates in b_event_message. The key is SPF, DKIM, DMARC on the DNS, otherwise transactional emails go to spam. We check deliverability and set up bounce handling.

How to Design Infoblocks for Performance?

We use Highload-blocks for reference data (colors, sizes, manufacturers) that are not involved in complex queries. For SKUs — a separate infoblock with linking via IBLOCK_ELEMENT_PROPERTY. Enable INDEX_PROPERTY for frequently filtered properties. Tagged caching: when an element changes, only the related cache is cleared. Highload-blocks process up to 10x faster than infoblocks with multiple properties on volumes of 100,000 records.

Custom Module Development

Each module follows the structure /local/modules/vendor.modulename/:

• install/index.php — setup class, create tables via $DB->RunSQLBatch()
• lib/ — D7 ORM classes, extending Bitrix\Main\ORM\Data\DataManager
• admin/ — administrative pages using CAdminList, CAdminForm
• include.php — autoloading, event handler registration via EventManager::getInstance()->registerEventHandler()
• REST API endpoints via \Bitrix\Rest\RestManager

The module registers in the system, appears in the "Installed Solutions" list, and has its own settings at /bitrix/admin/settings.php?mid=vendor.modulename. It can be enabled, disabled, and updated through UpdateSystem or custom migration mechanics.

Examples of implemented tasks:

• Campaign management — visual condition builder via CAdminCalendar, timers via agents (CAgent::AddAgent), analytics linked to the sale module
• Cost calculator — React widget on the frontend, REST API in the module, formulas stored in a Highload-block
• Booking system — real-time calendar, locking via $DB->StartTransaction() / $DB->Commit() on concurrent requests, integration with channel manager via webhook

Components and Composite Cache

Component customization via result_modifier.php and component_epilog.php, not by editing template.php of the standard template. This way core updates are painless.

Composite cache ("Composite Site" technology) — the server sends ready HTML, bypassing PHP routing. Dynamic areas (cart, authorization) are loaded via CBitrixComponent::setFrameMode(true) and AJAX. TTFB drops to 30–50 ms. But there are caveats: not all components are compatible, $APPLICATION->ShowPanel() breaks composite, and careful markup of <div id="bx-composite-..."> is required.

What to Check Before Installing a Marketplace Module?

Before installing a module from the marketplace, an audit is mandatory. We check: SQL queries without prepared statements (hello SQL injection), direct use of $_REQUEST without filtering, use of outdated kernel API instead of D7, conflicts with the composite cache module. A module with no updates for over a year and a few dozen installations is likely a problem on the next PHP update. A typical case: a module calls CIBlockElement::GetList with no cache reset — the site crashes with 5000 elements.

Migration to D7

When upgrading PHP or switching to a new edition — refactor outdated calls:

• CIBlockElement::GetList() → Bitrix\Iblock\Elements\ElementTable::getList()
• CSaleOrder::GetList() → Bitrix\Sale\Order::getList()
• CModule::IncludeModule() → Bitrix\Main\Loader::includeModule() Testing on staging, rollback via git on issues.

According to official 1C-Bitrix documentation, D7 ORM is the recommended tool for working with data, providing type safety and automatic query generation.

Comparison: Init.php vs Module

Module Development Scope and Cost

What is included in module development?

• Technical specification and architectural plan
• Code following PSR-4 and Bitrix code style
• Unit tests (PHPUnit) for business logic
• Integration tests for events and REST API
• Installation, configuration, and API documentation
• Repository and documentation access
• Administrator training for module usage
• 6-month warranty support

Estimated timelines and complexity:

Cost is calculated individually — contact us for a project estimate.

Module Testing

Unit tests via PHPUnit cover business logic: discount calculation, validation, document generation. Mocks for Bitrix\Main\Application::getConnection() allow tests to be DB-independent. Integration tests verify event handlers on a real database — OnAfterIBlockElementAdd, OnSaleOrderSaved, etc. REST API endpoints are tested via curl or PHPUnit HTTP client. Critical for modules working with b_sale_order, b_catalog_price — where errors cost money.

Compatibility is checked on PHP 7.4, 8.0, 8.1, 8.2 and editions: Standard, Small Business, Business. We check conflicts with popular marketplace modules — they often intercept the same events. Load testing: measurements on 10K, 100K, 1M records, profiling via Xdebug for memory leaks and N+1 queries.

Practical Examples

Campaign module for an electronics chain. The built-in sale module discounts did not cover scenarios like "2+1", a gift with purchase over a certain amount, or combined conditions. We built a visual builder: marketers create rules via drag-and-drop without development tickets. Campaign calendar, auto-deactivation via agents, analytics linked to b_sale_order — conversion, average check, usage count. Time to launch a new campaign dropped from two days to half an hour.

Calculator for builders. Parameters (area, materials, number of floors) → formula → preliminary estimate → lead to CRM via CRest::call('crm.lead.add'). Regional coefficients and seasonal markups from a Highload-block, material prices from 1C exchange. The number of target leads increased by a third: clients see a breakdown before calling a manager.

Booking for a hotel chain. Real-time availability via AJAX requests to a custom table vendor_booking_slots, seasonal tariff calculation, synchronization with Booking.com via channel manager API. Room locking on concurrent booking via SELECT ... FOR UPDATE in transactions. Timezones handled via \DateTimeZone — a guest from Vladivostok and a manager from Moscow see the same picture.

We will evaluate your project within one day. Write to us — we'll tell you what is included in turnkey development. Contact us for a consultation on your project. Order a custom module development — get a ready solution with documentation and support.