MergeTree Archives | ChistaDATA Inc.

ChistaDATA Performance

ClickHouse Performance Audit: 8 Best Tips for 26.8 LTS

ClickHouse performance audit tips for 26.8 LTS with real lab output: rank query shapes in system.query_log, measure cold past the query condition cache, read EXPLAIN ANALYZE and EXPLAIN WHATIF, and audit codecs per block.

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ClickHouse 26.8 LTS: What’s New for Real-Time Analytics (Tested)

ChistaDATA Inc.

ClickHouse 26.8 shipped on 27 August 2026 as the second LTS line of the year, and two days later the 25.8 LTS line dropped out of support. If you run 25.8 in production, you are […]

ClickHouse TTL: How Deletes Are Scheduled and 6 Reasons They Fail

ChistaDATA Inc.

A ClickHouse TTL clause is not a delete queue. There is no background reaper walking rows and checking expiry timestamps. A TTL expression on a MergeTree table is a promise that expired rows will be […]

ClickHouse Partition Pruning vs Primary Key: 3 Proven Gates

ChistaDATA Inc.

ClickHouse partition pruning and primary-key pruning are two different mechanisms that happen to show up on the same summary line of the server log, which is why so many people treat them as one thing. […]

Elasticsearch to ClickHouse for Logs and Observability: When and How to Switch

ChistaDATA Inc.

Elasticsearch to ClickHouse is the migration we scope most often in observability engagements, and the reason is rarely a feature gap — it is an economics gap. Elasticsearch became the default log store the way […]

The Snowflake Exit: A Migration Framework from Warehouse Credits to ClickHouse

ChistaDATA Inc.

Every quarter we take calls that start the same way: a data platform lead opens their Snowflake invoice, looks at the credit consumption graph, and asks what a Snowflake to ClickHouse migration would save. Sometimes […]

ClickHouse slow query troubleshooting: diagnosing query latency with system.query_log, a ChistaDATA production methodology

Diagnosing Slow ClickHouse Queries with system.query_log: A Production Methodology

ChistaDATA Inc.

Master ClickHouse slow query troubleshooting with a production-proven system.query_log methodology to find, classify, and fix query latency fast.

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ClickHouse Merge Performance: Diagnosing Too Many Parts, Slow Merges, and Stuck Mutations

ChistaDATA Inc.

ClickHouse merge performance is the hinge on which every high-ingest MergeTree deployment turns. When background merges keep pace with inserts, part counts stay flat and SELECT latency stays predictable. When they fall behind, the failure […]

ClickHouse MergeTree Optimization: Sort Keys, Partitioning, Skip Indexes, and Projections

ChistaDATA Inc.

ClickHouse MergeTree optimization is the difference between a table that answers analytical queries in milliseconds and one that scans hundreds of gigabytes for every request. This guide is written for senior engineers who already understand […]

ClickHouse IOPS Troubleshooting: A Complete Guide to Diagnosing and Fixing Disk I/O Bottlenecks

ChistaDATA Inc.

NEEDS FEATURED IMAGE. ClickHouse IOPS troubleshooting guide for DBAs and SREs: diagnose disk I/O bottlenecks with ClickHouse system tables, verify at the OS layer with iostat and pidstat, fix merge storms and part explosion, tune caches, tier storage, and monitor IOPS continuously with Prometheus and Grafana.

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