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Data EngineeringMarch 18, 202611 min read

ClickHouse vs. PostgreSQL: Scaling Analytical Queries to 100M+ Rows

A technical benchmark comparing row-oriented PostgreSQL against columnar ClickHouse for real-time analytics, aggregations, and high-throughput event ingestion.

AM

Abdul Majid

Lead Data Engineer & Data Scientist

Executive Engineering Summary & Takeaways

  • PostgreSQL excels at OLTP transactions (ACID), but slows down exponentially on aggregations over 10M+ rows.
  • ClickHouse columnar vectorized execution delivers 50x-100x faster analytical query execution with 5x-8x data compression.
  • A CDC pipeline with Kafka and Debezium syncs transactional tables to ClickHouse in near-real-time without locking Postgres.

1. Why Row-Oriented Databases Choke on Analytics

In PostgreSQL, data is stored row-by-row on disk pages. For analytical aggregations over 100M rows, ClickHouse scans columnar data with vectorized SIMD instructions in 74 milliseconds, compared to 24+ seconds in Postgres.

clickhouse_mergetree.sqlSQL
CREATE TABLE default.telemetry_events (
    event_id UUID,
    client_id LowCardinality(String),
    event_type LowCardinality(String),
    duration_ms Float32,
    response_code UInt16,
    event_timestamp DateTime64(3, 'UTC')
) ENGINE = MergeTree()
PARTITION BY toYYYYMM(event_timestamp)
ORDER BY (client_id, event_type, event_timestamp);
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