make GSI less shit

dynamodb/gsi.odin

@@ -20,6 +20,9 @@
 //   delete    → for each GSI, extract GSI key attrs from the OLD item, delete GSI entry
 //   update    → delete OLD GSI entries, write NEW GSI entries
 //
+// ATOMICITY: All GSI operations use WriteBatch to ensure that GSI entries are
+//            maintained atomically with the base item write/delete.
+//
 package dynamodb
 
 import "core:slice"
@@ -156,14 +159,95 @@ gsi_project_item :: proc(
 }
 
 // ============================================================================
-// GSI Write Maintenance
+// GSI Write Maintenance - ATOMIC via WriteBatch
 //
-// Called after a successful data write to maintain GSI entries.
-// Uses WriteBatch for atomicity (all GSI entries for one item in one batch).
+// These procedures add GSI operations to a WriteBatch instead of performing
+// direct database writes. This ensures atomicity with the base item operation.
 // ============================================================================
 
+// Add GSI write operations to a WriteBatch for an item across all GSIs.
+// Called during put_item or update_item to maintain NEW GSI entries.
+gsi_batch_write_entries :: proc(
+	batch: ^rocksdb.WriteBatch,
+	table_name: string,
+	item: Item,
+	metadata: ^Table_Metadata,
+) -> Storage_Error {
+	gsis, has_gsis := metadata.global_secondary_indexes.?
+	if !has_gsis || len(gsis) == 0 {
+		return .None
+	}
+
+	for &gsi in gsis {
+		// Extract GSI key from item
+		gsi_kv, kv_ok := gsi_extract_key_values(item, gsi.key_schema)
+		if !kv_ok {
+			continue // Sparse: item doesn't have GSI PK, skip
+		}
+
+		// Build GSI storage key
+		gsi_storage_key := build_gsi_key(table_name, gsi.index_name, gsi_kv.pk, gsi_kv.sk)
+		defer delete(gsi_storage_key)
+
+		// Build projected item
+		projected := gsi_project_item(item, &gsi, metadata.key_schema)
+		defer item_destroy(&projected)
+
+		// Encode projected item
+		encoded, encode_ok := encode(projected)
+		if !encode_ok {
+			return .Serialization_Error
+		}
+		defer delete(encoded)
+
+		// Add to batch (not written yet)
+		rocksdb.batch_put(batch, gsi_storage_key, encoded)
+	}
+
+	return .None
+}
+
+// Add GSI delete operations to a WriteBatch for an item across all GSIs.
+// Called during delete_item or update_item to remove OLD GSI entries.
+// Needs the OLD item to know which GSI keys to remove.
+gsi_batch_delete_entries :: proc(
+	batch: ^rocksdb.WriteBatch,
+	table_name: string,
+	old_item: Item,
+	metadata: ^Table_Metadata,
+) -> Storage_Error {
+	gsis, has_gsis := metadata.global_secondary_indexes.?
+	if !has_gsis || len(gsis) == 0 {
+		return .None
+	}
+
+	for &gsi in gsis {
+		gsi_kv, kv_ok := gsi_extract_key_values(old_item, gsi.key_schema)
+		if !kv_ok {
+			continue // Item didn't have a GSI entry
+		}
+
+		gsi_storage_key := build_gsi_key(table_name, gsi.index_name, gsi_kv.pk, gsi_kv.sk)
+		defer delete(gsi_storage_key)
+
+		// Add to batch (not written yet)
+		rocksdb.batch_delete(batch, gsi_storage_key)
+	}
+
+	return .None
+}
+
+// ============================================================================
+// DEPRECATED - Non-atomic GSI maintenance
+//
+// These procedures are kept for backwards compatibility but should NOT be used.
+// They perform individual database writes which is NOT atomic.
+// Use gsi_batch_write_entries and gsi_batch_delete_entries instead.
+// ============================================================================
+
+// DEPRECATED: Use gsi_batch_write_entries instead for atomic operations.
 // Write GSI entries for an item across all GSIs defined on the table.
-// Should be called AFTER the main data key is written.
+// WARNING: This performs individual writes which is NOT atomic!
 gsi_write_entries :: proc(
 	engine: ^Storage_Engine,
 	table_name: string,
@@ -207,9 +291,9 @@ gsi_write_entries :: proc(
 	return .None
 }
 
+// DEPRECATED: Use gsi_batch_delete_entries instead for atomic operations.
 // Delete GSI entries for an item across all GSIs.
-// Should be called BEFORE or AFTER the main data key is deleted.
-// Needs the OLD item to know which GSI keys to remove.
+// WARNING: This performs individual writes which is NOT atomic!
 gsi_delete_entries :: proc(
 	engine: ^Storage_Engine,
 	table_name: string,