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ADR 0002: MySQL is a read-only source

Status​

Accepted

Context​

The project still needs to ingest data from existing MySQL-hosted OMOP datasets, but maintaining MySQL write behavior complicates the system and is no longer required.

Decision​

When SOURCE_TYPE=mysql, the importer may only read from MySQL.

The code:

  • discovers tables with SHOW TABLES
  • inspects columns with SELECT * FROM table LIMIT 0
  • streams rows with SELECT * FROM table
  • recreates the data in SQLite

Consequences​

Positive:

  • reduced operational risk
  • lower permission requirements (SELECT only)
  • clearer architecture

Tradeoffs:

  • importing from MySQL adds a copy step before downstream processing
  • debugging source data still sometimes requires looking at the MySQL origin directly