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67 lines
2.8 KiB
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67 lines
2.8 KiB
Plaintext
---
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id: pgmustard
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title: 'pgMustard'
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description: 'Troubleshoot slow queries on Supabase with pgMustard, a visualization tool that also gives advice.'
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---
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This guide explains how to troubleshoot slow queries on Supabase using `explain` and pgMustard.
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[pgMustard](https://pgmustard.com/) is a visualization tool for [`explain analyze`](https://www.postgresql.org/docs/current/using-explain.html#USING-EXPLAIN-ANALYZE) that also gives performance tips.
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## Step 1: Get the query plan from Supabase
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Use `explain analyze` to get a query plan from Postgres. This will run the query behind the scenes, so be careful with data modification queries.
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pgMustard requires plans to be in json format, and the buffers, verbose, and settings parameters allow it to give better tips.
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So a good prefix for your query would be:
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```jsx
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explain (analyze, format json, buffers, verbose, settings)
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```
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Run the query, and copy the output.
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If you’re using the Supabase SQL Editor, this is easily copied from the cell titled `QUERY PLAN`, as seen above.
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If you have any trouble, check out pgMustard’s guide for [getting a query plan](https://www.pgmustard.com/getting-a-query-plan).
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## Step 2: Paste the query plan into pgMustard
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Paste the json output into pgMustard and press Submit.
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## Step 3: Look through the top tips and slowest operations
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Review the top tips in pgMustard. These are scored on a scale of 0 to 5 stars, based on how much time-saving potential they have (5 stars meaning lots of potential).
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Click one of the tips, or one of the operations, to see more information.
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## Step 4: Consider your options
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If you get some promising suggestions, you may wish to explore them.
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If you don’t get any tips, your query might be quite fast for the amount of work it’s doing.
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For the example we saw in Step 3, let's try adding an index on the `customer_name` field in Supabase.
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Going through Steps 1-3 again, we now get an efficient index scan, that will scale nicely as our data grows.
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We could look into why Postgres isn’t choosing to do an index-only scan here, but pgMustard is letting us know that it doesn’t think we’ll gain much by doing so, by scoring the tip 0.3 out of 5.
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## Resources
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- [pgMustard](https://www.pgmustard.com) official website.
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- [pgMustard explain glossary](https://www.pgmustard.com/docs/explain).
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