feat(sql): arg_min and arg_max CHAR functions by nwoolmer · Pull Request #6730 · questdb/questdb

nwoolmer · 2026-01-30T15:35:14Z

Summary

Adds arg_max and arg_min function variants that accept a CHAR type for the value argument (left-hand side).

New functions

Function	Signature	Description
`arg_max(AN)`	`arg_max(char, timestamp)`	Returns char value at maximum timestamp
`arg_max(AL)`	`arg_max(char, long)`	Returns char value at maximum long
`arg_max(AD)`	`arg_max(char, double)`	Returns char value at maximum double
`arg_min(AN)`	`arg_min(char, timestamp)`	Returns char value at minimum timestamp
`arg_min(AL)`	`arg_min(char, long)`	Returns char value at minimum long
`arg_min(AD)`	`arg_min(char, double)`	Returns char value at minimum double

Usage examples

-- Find char value at maximum/minimum timestamp
SELECT arg_max(status, created_at), arg_min(status, created_at) FROM events;

-- With GROUP BY
SELECT category, arg_max(grade, score), arg_min(grade, score)
FROM results
GROUP BY category;

Notes

Null keys are ignored during aggregation
Null values are returned when the corresponding key is the max/min
All variants support parallel execution

coderabbitai · 2026-01-30T15:35:28Z

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Walkthrough

Adds eight new group-by aggregation functions implementing arg_max and arg_min for char values across three key types (double, long, timestamp), with corresponding function factories and comprehensive test suites.

Changes

Cohort / File(s)	Summary
ArgMax Char with Double Key `core/src/main/java/io/questdb/griffin/engine/functions/groupby/ArgMaxCharDoubleGroupByFunction.java`, `ArgMaxCharDoubleGroupByFunctionFactory.java`	Implements arg_max aggregation that tracks maximum double key with corresponding char value; factory exposes signature `arg_max(AD)`.
ArgMax Char with Long Key `core/src/main/java/io/questdb/griffin/engine/functions/groupby/ArgMaxCharLongGroupByFunction.java`, `ArgMaxCharLongGroupByFunctionFactory.java`	Implements arg_max aggregation that tracks maximum long key with corresponding char value; factory exposes signature `arg_max(AL)`.
ArgMax Char with Timestamp Key `core/src/main/java/io/questdb/griffin/engine/functions/groupby/ArgMaxCharTimestampGroupByFunction.java`, `ArgMaxCharTimestampGroupByFunctionFactory.java`	Implements arg_max aggregation that tracks maximum timestamp key with corresponding char value; factory exposes signature `arg_max(AN)`.
ArgMin Char with Double Key `core/src/main/java/io/questdb/griffin/engine/functions/groupby/ArgMinCharDoubleGroupByFunction.java`, `ArgMinCharDoubleGroupByFunctionFactory.java`	Implements arg_min aggregation that tracks minimum double key with corresponding char value; factory exposes signature `arg_min(AD)`.
ArgMin Char with Long Key `core/src/main/java/io/questdb/griffin/engine/functions/groupby/ArgMinCharLongGroupByFunction.java`, `ArgMinCharLongGroupByFunctionFactory.java`	Implements arg_min aggregation that tracks minimum long key with corresponding char value; factory exposes signature `arg_min(AL)`.
ArgMin Char with Timestamp Key `core/src/main/java/io/questdb/griffin/engine/functions/groupby/ArgMinCharTimestampGroupByFunction.java`, `ArgMinCharTimestampGroupByFunctionFactory.java`	Implements arg_min aggregation that tracks minimum timestamp key with corresponding char value; factory exposes signature `arg_min(AN)`.
Test Suite `core/src/test/java/io/questdb/test/griffin/engine/functions/groupby/ArgMaxCharDoubleGroupByFunctionFactoryTest.java`, `ArgMaxCharLongGroupByFunctionFactoryTest.java`, `ArgMaxCharTimestampGroupByFunctionFactoryTest.java`, `ArgMinCharDoubleGroupByFunctionFactoryTest.java`, `ArgMinCharLongGroupByFunctionFactoryTest.java`, `ArgMinCharTimestampGroupByFunctionFactoryTest.java`	Comprehensive test coverage for all six variants including null handling, parallel execution, chunked data processing, group-by scenarios, and merge operations.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

feat(sql): add arg_min() and arg_max() aggregate functions #6652: Adds related arg_min/arg_max group-by aggregation functions in the same package with comparable function patterns and MapValue-based aggregation logic.

Suggested labels

New feature

Suggested reviewers

bluestreak01
puzpuzpuz

🚥 Pre-merge checks | ✅ 1 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	❓ Inconclusive	No pull request description was provided by the author, making it impossible to assess whether it relates to the changeset.	Add a pull request description explaining the motivation, implementation details, and testing approach for the new CHAR-typed arg_min/arg_max functions.

✅ Passed checks (1 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly and concisely describes the main change: adding arg_min and arg_max functions for CHAR data type in SQL.

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Commit unit tests in branch nw_arg_min_max_char

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nwoolmer · 2026-01-30T15:35:58Z

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coderabbitai · 2026-01-30T15:36:08Z

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coderabbitai · 2026-01-30T16:06:04Z

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glasstiger · 2026-03-04T14:31:19Z

...ain/java/io/questdb/griffin/engine/functions/groupby/ArgMinCharTimestampGroupByFunction.java

+    public void computeFirst(MapValue mapValue, Record record, long rowId) {
+        long key = keyArg.getTimestamp(record);
+        if (key == Numbers.LONG_NULL) {
+            mapValue.putChar(valueIndex, (char) 0);


nit:
(char) 0 is hardcoded in 6 files instead of using Numbers.CHAR_NULL.
Not a bug (they are the same value), but using the constant would be more self-documenting.
The existing codebase uses Numbers.LONG_NULL and Double.NaN for those types, so the CHAR variant is slightly inconsistent.

Fixed — replaced all (char) 0 occurrences with Numbers.CHAR_NULL across all 6 implementation files (in computeFirst() and setNull()).

...uestdb/test/griffin/engine/functions/groupby/ArgMaxCharDoubleGroupByFunctionFactoryTest.java

Use Numbers.CHAR_NULL instead of hardcoded (char) 0 across all 6 implementation files for consistency with Numbers.LONG_NULL and Double.NaN usage in other arg_min/arg_max variants. Add missing test coverage: empty table, tie-breaking behavior (first occurrence wins with strict >/<), and mixed null value + null key combinations in the same dataset. Co-Authored-By: Claude Opus 4.6 <[email protected]>

glasstiger · 2026-03-09T23:19:37Z

[PR Coverage check]

😍 pass : 288 / 288 (100.00%)

file detail

	path	covered line	new line	coverage
🔵	io/questdb/griffin/engine/functions/groupby/ArgMinCharTimestampGroupByFunction.java	44	44	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMaxCharTimestampGroupByFunction.java	44	44	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMaxCharTimestampGroupByFunctionFactory.java	4	4	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMaxCharLongGroupByFunctionFactory.java	4	4	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMaxCharLongGroupByFunction.java	44	44	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMinCharDoubleGroupByFunctionFactory.java	4	4	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMaxCharDoubleGroupByFunctionFactory.java	4	4	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMinCharTimestampGroupByFunctionFactory.java	4	4	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMinCharLongGroupByFunction.java	44	44	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMinCharLongGroupByFunctionFactory.java	4	4	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMaxCharDoubleGroupByFunction.java	44	44	100.00%
🔵	io/questdb/griffin/engine/functions/groupby/ArgMinCharDoubleGroupByFunction.java	44	44	100.00%

additional arg_min/arg_max functions for LHS CHAR argument

b0fcfc9

nwoolmer added the SQL Issues or changes relating to SQL execution label Jan 30, 2026

nwoolmer and others added 2 commits February 16, 2026 17:46

Merge branch 'master' into nw_arg_min_max_char

92d29cf

Merge branch 'master' into nw_arg_min_max_char

c3cd0ad

glasstiger reviewed Mar 4, 2026

View reviewed changes

...uestdb/test/griffin/engine/functions/groupby/ArgMaxCharDoubleGroupByFunctionFactoryTest.java Show resolved Hide resolved

bluestreak01 and others added 2 commits March 9, 2026 18:50

Merge branch 'master' into nw_arg_min_max_char

90f4c2c

bluestreak01 approved these changes Mar 9, 2026

View reviewed changes

bluestreak01 merged commit cb5c781 into master Mar 13, 2026
50 checks passed

bluestreak01 deleted the nw_arg_min_max_char branch March 13, 2026 11:35

maciulis pushed a commit to maciulis/questdb that referenced this pull request Mar 16, 2026

feat(sql): arg_min and arg_max CHAR functions (questdb#6730)

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feat(sql): arg_min and arg_max CHAR functions#6730

feat(sql): arg_min and arg_max CHAR functions#6730
bluestreak01 merged 5 commits intomasterfrom
nw_arg_min_max_char

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Summary

New functions

Usage examples

Notes

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