Exploring pg_tables
In order to make a query plan, the query planner needs basic information like table names, column names, and the number of rows of each table or view. Without this information, the planner would not know how many rows to search to find a specific columns used in filter conditions. It would not know if it can use an index search.
This type of metadata is stored in the pg_tables schema. Specifically, the planner uses pg_class and pg_stats. Take a look to see what kind of information these objects contain.
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Improving Query Performance in PostgreSQL
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SELECT ___ -- Index indicator column
FROM pg_class
WHERE relname = 'daily_aqi';