feat(core): add `em.countBy()` for grouped counting by B4nan · Pull Request #7372 · mikro-orm/mikro-orm

B4nan · 2026-03-21T17:40:03Z

Summary

Adds em.countBy(entityName, groupBy, options?) — counts entities grouped by one or more properties, returning Dictionary<number>
Type-safe groupBy parameter (EntityKey<Entity> | readonly EntityKey<Entity>[])
For composite groupBy, result keys are joined with ~~~ (Utils.PK_SEPARATOR)
SQL: single GROUP BY query via QueryBuilder
MongoDB: aggregation pipeline with $group + $sum
Also available on EntityRepository via repo.countBy(groupBy, options?)
New CountByOptions type extends CountOptions (without groupBy) and adds where

const counts = await em.countBy(Book, 'author');
// { '1': 2, '2': 1, '3': 3 }

const counts = await em.countBy(Order, ['status', 'country']);
// { 'pending~~~US': 5, 'shipped~~~DE': 3 }

🤖 Generated with Claude Code

codecov · 2026-03-21T17:43:24Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.65%. Comparing base (b546277) to head (0711057).
⚠️ Report is 2 commits behind head on next.

Additional details and impacted files

@@           Coverage Diff            @@
##             next    #7372    +/-   ##
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  Coverage   99.65%   99.65%            
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  Files         263      263            
  Lines       26888    26942    +54     
  Branches     6985     7455   +470     
========================================
+ Hits        26794    26848    +54     
  Misses         88       88            
  Partials        6        6

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Adds `em.countBy(entityName, groupBy, options?)` — counts entities grouped by one or more properties, returning `Dictionary<number>`. For composite `groupBy`, result keys are joined with `~~~`. SQL drivers issue a single GROUP BY query via QueryBuilder. MongoDB uses an aggregation pipeline with `$group` + `$sum`. Also available on repositories via `repo.countBy(groupBy, options?)`. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- SQL/MongoDB countBy now calls processWhere (applies entity filters and discriminator conditions) and tryFlush (honors FlushMode.AUTO/ALWAYS) - MongoDB countBy routes through driver.aggregate() for transaction context, query logging, and error wrapping; applies renameFields to the where clause for correct field name mapping - Trim CountByOptions to only relevant properties instead of inheriting all of CountOptions - Fix unquoted SQL alias for MySQL compatibility - Move SQL countBy tests to dedicated test file with filter coverage Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Call prepareOptions() in both SQL and MongoDB countBy so EM-level schema defaults and logger context are inherited (matching every other EM method) - Throw when `having` is passed to MongoDB countBy instead of silently ignoring it - Add test for nullable groupBy columns (null publisher key) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Exercise the remaining branches of the new `countBy` API so the PR reaches 100% patch coverage on the touched source files: - base `EntityManager.countBy` throw for drivers that don't override it - SQL `having`/`schema` option paths - SQL/Mongo raw-field fallback when groupBy isn't a declared property - Mongo composite groupBy pipeline - Mongo `having` rejection

## Summary - Adds dataloader batching for `Collection.loadCount()` — multiple count calls in the same tick are grouped into a single query - 1:M relations: uses `em.countBy()` for a single GROUP BY query - M:N relations: falls back to parallel `em.count()` calls (entity filters correctly applied) - Adds `dataloader` option to `LoadCountOptions`, respects global `DataloaderType.ALL`/`COLLECTION` config Depends on #7372. Closes #6425 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

## Summary - Adds `em.countBy(entityName, groupBy, options?)` — counts entities grouped by one or more properties, returning `Dictionary<number>` - Type-safe `groupBy` parameter (`EntityKey<Entity> | readonly EntityKey<Entity>[]`) - For composite `groupBy`, result keys are joined with `~~~` (`Utils.PK_SEPARATOR`) - SQL: single `GROUP BY` query via QueryBuilder - MongoDB: aggregation pipeline with `$group` + `$sum` - Also available on `EntityRepository` via `repo.countBy(groupBy, options?)` - New `CountByOptions` type extends `CountOptions` (without `groupBy`) and adds `where` ```ts const counts = await em.countBy(Book, 'author'); // { '1': 2, '2': 1, '3': 3 } const counts = await em.countBy(Order, ['status', 'country']); // { 'pending~~~US': 5, 'shipped~~~DE': 3 } ``` 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

## Summary - Adds dataloader batching for `Collection.loadCount()` — multiple count calls in the same tick are grouped into a single query - 1:M relations: uses `em.countBy()` for a single GROUP BY query - M:N relations: falls back to parallel `em.count()` calls (entity filters correctly applied) - Adds `dataloader` option to `LoadCountOptions`, respects global `DataloaderType.ALL`/`COLLECTION` config Depends on #7372. Closes #6425 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

## Summary - Adds `em.countBy(entityName, groupBy, options?)` — counts entities grouped by one or more properties, returning `Dictionary<number>` - Type-safe `groupBy` parameter (`EntityKey<Entity> | readonly EntityKey<Entity>[]`) - For composite `groupBy`, result keys are joined with `~~~` (`Utils.PK_SEPARATOR`) - SQL: single `GROUP BY` query via QueryBuilder - MongoDB: aggregation pipeline with `$group` + `$sum` - Also available on `EntityRepository` via `repo.countBy(groupBy, options?)` - New `CountByOptions` type extends `CountOptions` (without `groupBy`) and adds `where` ```ts const counts = await em.countBy(Book, 'author'); // { '1': 2, '2': 1, '3': 3 } const counts = await em.countBy(Order, ['status', 'country']); // { 'pending~~~US': 5, 'shipped~~~DE': 3 } ``` 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

## Summary - Adds dataloader batching for `Collection.loadCount()` — multiple count calls in the same tick are grouped into a single query - 1:M relations: uses `em.countBy()` for a single GROUP BY query - M:N relations: falls back to parallel `em.count()` calls (entity filters correctly applied) - Adds `dataloader` option to `LoadCountOptions`, respects global `DataloaderType.ALL`/`COLLECTION` config Depends on #7372. Closes #6425 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

B4nan mentioned this pull request Mar 21, 2026

feat(core): add dataloader support for Collection.loadCount() #7373

Merged

B4nan force-pushed the feat/count-by branch from 26c27a0 to 6c7189c Compare March 21, 2026 20:35

B4nan force-pushed the feat/count-by branch 2 times, most recently from 2dcf6fe to 3b6d014 Compare April 1, 2026 14:53

B4nan force-pushed the feat/count-by branch 2 times, most recently from ad5be5b to cfbd345 Compare April 18, 2026 15:22

B4nan changed the base branch from master to next April 18, 2026 15:22

B4nan and others added 4 commits April 18, 2026 17:43

B4nan force-pushed the feat/count-by branch from cfbd345 to 0711057 Compare April 18, 2026 15:45

B4nan merged commit 802fe72 into next Apr 18, 2026
20 checks passed

B4nan deleted the feat/count-by branch April 18, 2026 16:19

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feat(core): add `em.countBy()` for grouped counting#7372

feat(core): add `em.countBy()` for grouped counting#7372
B4nan merged 4 commits intonextfrom
feat/count-by

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B4nan commented Mar 21, 2026 •

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