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I'm surprised covering indices is only now appearing in 11. It's fairly commonplace in other databases.
by wenc 8y ago
I'm surprised covering indices is only now appearing in 11. It's fairly commonplace in other databases.
- geophile 8y agoI believe HOT provided some of the advantages of covering indexes. Covering indexes is tricky in Postgres, due to its MVCC implementation. Versioning info is in the table, not the index, so the index may have stale data. The table itself has to be consulted to find out if the data in the index is actually visible to your transaction.
- petergeoghegan 8y agoYou're talking about index-only scans. Those appeared in Postgres 9.2, which came out about 5 years ago. INCLUDE/covering indexes are indexes that can include extra "payload" columns, and exist only for the benefit of index-only scans. You can add something extra to the primary key for the largest table in your database, all without changing how and when duplicate violation errors are raised.
- polskibus 8y agoI wonder if it will lead to finally implementing clustered index in pgsql and breaking he last major obstacle to match performance with MS SQL.