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Step 1: Enable log_explain

We generally recommend using auto_explain to collect EXPLAIN plans automatically, but Heroku does not support the required auto_explain module, so we offer an alternative, log-based, EXPLAIN mechanism.

The log-based EXPLAIN mechanism works by watching your logs for slow queries (according to log_min_duration_statement) and running EXPLAIN for each one. This has some limitations (most notably, we only run EXPLAIN, not EXPLAIN ANALYZE), but still provides valuable insights. Learn more in our Log-based EXPLAIN overview.

Once Log Insights is working, enabling EXPLAIN plan collection just requires turning on the collector setting. You can do this by setting a config var on your Heroku app:

$ heroku config:set PGA_ENABLE_LOG_EXPLAIN=true -a [your-collector-app-name]

This will show output like the following:

Setting PGA_ENABLE_LOG_EXPLAIN and restarting ⬢ [your-collector-app-name]... done, v42
PGA_ENABLE_LOG_EXPLAIN: true
Proceed to Step 2: Test and verify

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