covering index
Include the values a query needs so fewer table-row fetches may be necessary.
Use this when An indexed query still spends time fetching columns from the table.
without the term
“The query finds matches quickly but still fetches many table rows for extra columns. Reduce those fetches if worthwhile.”
with the term · How do you ask a model for covering index?
Evaluate a covering index for this query. Verify index-only eligibility, heap fetches, index size, and write cost.
What is covering index?
A covering index contains the columns required by a particular query. PostgreSQL can use INCLUDE for payload columns, but MVCC visibility can still require heap checks in an index-only scan.
Why does covering index matter when vibe coding?
An agent can add every column to an index or promise that coverage always eliminates heap reads.
How do you do covering index?
Check filters, ordering, and selected columns. Compare index size, write overhead, and actual heap fetches on representative data and update rates.
What goes wrong with covering index?
Coverage is relative to a query. Visibility, unsupported access methods, or changed projections can remove its benefit.
Sources for this entry
- PostgreSQL: Index-only scans and covering indexes
Secondary indexes, payload columns, and visibility checks required for index-only scans.
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