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82 lines
2.4 KiB
Markdown
82 lines
2.4 KiB
Markdown
# doctrine-orm-0003 — SqlWalker::walkObjectExpression: O(fields²) partial field set check per query
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**Status:** OPEN
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**Severity:** MEDIUM
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**Component:** `doctrine/orm` — `src/Doctrine/ORM/Query/SqlWalker.php`
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**Affects:** DQL queries using partial object selects (`SELECT PARTIAL p.{id,name}`)
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---
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## Root Cause
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`SqlWalker.php:1405` and `1445` — `walkObjectExpression()`:
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```php
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// DEFECTIVE — O(partialFieldSet) per field, inside foreach fieldMappings
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foreach ($class->fieldMappings as $fieldName => $mapping) {
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if ($partialFieldSet && ! in_array($fieldName, $partialFieldSet, true)) {
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continue;
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}
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// ... build SQL column list
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}
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// And for subclasses (line 1445):
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foreach ($subClass->fieldMappings as $fieldName => $mapping) {
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if (isset($mapping->inherited) || ($partialFieldSet && ! in_array($fieldName, $partialFieldSet, true))) {
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continue;
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}
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```
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`$partialFieldSet` is a plain PHP array of field name strings. For each field in
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`$class->fieldMappings` (F fields), `in_array` scans all P entries in `$partialFieldSet`.
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Total: O(F × P) per class, O(F × P × subclasses) for STI/CTI hierarchies.
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Called once per query compilation (not per result row), but DQL parsing without a query
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result cache repeats this on every request.
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---
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## Complexity Analysis
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| Metric | Defective | Fixed |
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|--------|-----------|-------|
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| Single field check | O(partialFieldSet size P) | O(1) |
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| Full entity (F fields) | O(F × P) | O(F) |
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| With S subclasses (STI) | O(F × P × S) | O(F × S) |
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---
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## Fix
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Convert `$partialFieldSet` array to a hash set before entering the loop:
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```php
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// FIXED — build O(1)-lookup set once, before the loops
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$partialFieldIndex = $partialFieldSet ? array_flip($partialFieldSet) : null;
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foreach ($class->fieldMappings as $fieldName => $mapping) {
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if ($partialFieldIndex !== null && ! isset($partialFieldIndex[$fieldName])) {
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continue;
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}
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// ...
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}
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```
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Same fix applies at line 1445 for the subclass loop.
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---
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## Call Sites
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| File | Line | Context |
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|------|------|---------|
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| `src/Query/SqlWalker.php` | 1405 | `walkObjectExpression()` — primary class fields |
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| `src/Query/SqlWalker.php` | 1445 | `walkObjectExpression()` — STI/CTI subclass fields |
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---
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## Speedup Estimate
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Queries with large partial field sets (P > 10) or large entities (F > 20) with deep STI
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hierarchies (S > 10): O(P)× improvement in query compilation time on the partial-select
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field filter path.
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