Implementation details for EF Core SaveChanges and the update pipeline. Use when changing CommandBatchPreparer, UpdateSqlGenerator, ModificationCommand, or related classes.
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---
name: update-pipeline
description: 'Implementation details for EF Core SaveChanges and the update pipeline. Use when changing CommandBatchPreparer, UpdateSqlGenerator, ModificationCommand, or related classes.'
user-invocable: false
---
# Update Pipeline
Converts tracked entity changes into database INSERT/UPDATE/DELETE commands during `SaveChanges()`.
## Flow
`SaveChanges()` → `DetectChanges()` → `IDatabase.SaveChanges()` → `UpdateAdapter` creates `IUpdateEntry` list → `CommandBatchPreparer.BatchCommands()`
→ `ModificationCommand` per table row, composed of `ColumnModification` per column
→ `SharedTableEntryMap` is used to track entries mapped to the same row
→ Topological sort via Multigraph (FK dependency ordering)
→ Groups into `ModificationCommandBatch` (respects max batch size)
→ `UpdateSqlGenerator` generates SQL per batch → `BatchExecutor` executes all batches in a transaction → `StateManager.AcceptAllChanges()`
## Concurrency
Concurrency tokens → WHERE conditions on UPDATE/DELETE. `AffectedCountModificationCommandBatch` checks affected rows. Throws `DbUpdateConcurrencyException` on mismatch.
## Validation
- `SaveChanges()` returns expected affected row count
- Store-generated values propagate back to entities after INSERT/UPDATE
- `DbUpdateConcurrencyException` thrown when expected for stale data
