Türker Yıldırım

migrations

  • A copy tool rejected because of a trigger

    Note2 min read

    An online schema change tool that works by adding triggers, on a table an outbox relay polls. The tool is well understood and the interaction with an existing…

  • A search index rebuilt because the mapping changed again

    Note1 min read

    A field that had to change type for the second time in eighteen months, and a rebuild that is now routine. The rebuild time is what makes a…

  • A schema change on a table nobody can lock

    Deep dive10 min read

    A column type change on a table taking four hundred writes a second, and an ALTER that estimates four hours.

  • The API version that was finally decommissioned

    Note2 min read

    Version 1, deprecated in March 2025 with a sunset date of December, switched off in January. Nine months of overlap and the date still moved by a fortnight,…

  • Retention split by class, on 900 million rows

    Note2 min read

    One table with two retention requirements, seven years apart, and no column distinguishing them. The technical work was a generated column and a backfill; the work that took…

  • Anonymising rows that must be kept and must not identify

    Note1 min read

    Financial records retained for seven years, containing personal data that may not be retained that long. Keeping the postcode district and discarding the rest is the compromise that…

  • The archive table nobody could delete from

    Deep dive10 min read

    900 million rows, a retention policy, and a legal question nobody had asked. A table that grows forever because deleting from it might be illegal.

  • The read model that finally earned its place

    Deep dive10 min read

    A projection deleted in 2023 for being premature, rebuilt in 2025 because the query is now eleven seconds.

  • Testing a migration forwards on a copy of production

    Note2 min read

    A migration tested against an empty schema, run against nine hundred million rows, and taking four hours instead of four seconds. The restore drill already produced a full…

  • Managing WordPress entirely through Composer

    Deep dive15 min read

    turkerdev/wp-composer, and an install where nothing is committed except a lock file. Core, themes and plugins as dependencies.