Archive
indexes
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MySQL 5.7 JSON columns, and the regrets that followed
A support lookup read 2.4 million rows to return 41 of them, because the predicate sat inside a JSON document. The generated column fix, the two details that broke it first, and what I keep out of documents now.
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EXPLAIN, and the report that took forty seconds
A finance report on the ERP took 41 seconds against 1.9 million invoices. The slow query log, EXPLAIN, one index that was never used, and the composite index that finally worked on MySQL 5.5.