Add docs for ntile, cume_dist, and nth_value window functions#430
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Add docs for ntile, cume_dist, and nth_value window functions#430jovfer wants to merge 4 commits into
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Document the three new window functions added in questdb/questdb#6925. Cover argument and frame rules, edge cases, error conditions, and tabular examples mirroring the PR's test data. Update the overview quick reference and remove the stale "not currently supported" note from the reference. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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🚀 Build success! Latest successful preview: https://preview-430--questdb-documentation.netlify.app/docs/ Commit SHA: 908c54a
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This was referenced May 7, 2026
- Remove epoch-era timestamps from synthetic examples, use current dates - Replace [$today] bracket syntax with $today across all queries - Improve cume_dist demo query with single-symbol filter and DESC ordering - Clarify nth_value relationship to lag (frame-relative vs row-relative) - Remove unsupported FROM FIRST/FROM LAST mentions from nth_value - Remove internal implementation notes about type overloads - Use abbreviated ROWS N PRECEDING frame syntax - Fix em dash and dash-separator style across the file
javier
approved these changes
May 8, 2026
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Summary
Documents the three new window functions added in questdb/questdb#6925:
ntile(n)— distributes rows of an ordered partition intonapproximately equal buckets and returns the 1-based bucket number.cume_dist()— returns the cumulative distribution of the current row (including peers) within the partition.nth_value(value, n)— returns then-th value (1-based) within the current window frame, orNULLwhen the frame is smaller thann. Currentlydouble-only;LONG/TIMESTAMPoverloads are tracked in feat(sql): add nth_value support for LONG and TIMESTAMP arguments questdb#7037.Each section calls out the actual rules from the PR —
nmust be a constant, framing is rejected forntile/cume_dist,nth_valuerejectsIGNORE NULLS/RESPECT NULLS/FROM FIRST/FROM LAST, etc. Tabular examples mirror the test data inWindowFunctionTest.Also:
ntile()andcume_dist()are not currently supported" line from the bottom Notes and replaced it with a note aboutnth_valuebeingdouble-only for now.Test plan
yarn buildsucceedsquery/functions/window-functions/overview.mdandquery/functions/window-functions/reference.md#nth_value,#cume_dist,#ntileresolve from the overview quick-reference table🤖 Generated with Claude Code