feat(engine): extend Executor with buildInsertRow

src/main/kotlin/kestrel/engine/Executor.kt

@@ -1303,13 +1303,41 @@ class Executor(private val catalog: Catalog) : SequenceAccess {
                 ForeignKeyEnforcer.validateRow(catalog, schema, row.values, uncommittedSiblings = newRows)
                 enforceChecks(schema, row)
             }
+            enforcePrimaryKeyUniqueness(schema, table.rows + newRows)
+            enforceUniqueConstraints(schema, table.rows + newRows)
+            enforceUniqueIndexes(schema, table.rows + newRows)
+            table.rows.addAll(newRows)
+            catalog.reindexTable(schema.name)
+            fireRowTriggers(schema, TriggerTiming.After, TriggerEvent.Insert, newRows.map { null to it })
+            val returning = statement.returning?.let { evaluateReturning(schema, newRows, it) }
+            return InsertResult(newRows.size, returning)
+        }
+        return executeInsertWithConflictHandling(schema, table, newRows, onConflict, statement.returning, triggerContext)
+    }
+
+    private fun buildInsertRow(
+        schema: TableSchema,
+        targetIndices: List<Int>,
+        rawRow: List<Expression?>,
+        evaluator: Evaluator
+    ): Row {
+        if (rawRow.size != targetIndices.size) {
+            throw KestrelException(
+                "table ${schema.name} expects ${targetIndices.size} values but ${rawRow.size} were supplied"
+            )
+        }
         val values = MutableList<Value>(schema.columns.size) { Value.NullValue }
+        val touched = BooleanArray(schema.columns.size)
         for ((position, expression) in rawRow.withIndex()) {
             val columnIndex = targetIndices[position]
+            // A literal DEFAULT in the VALUES list is left untouched here, exactly like a
+            // column missing from an explicit INSERT column list - both fall through to the
+            // same default-filling loop below, matching UPDATE ... SET col = DEFAULT semantics.
+            if (expression != null) {
+                rejectGeneratedAssignment(schema.columns[columnIndex], explicitValueGiven = true)
                 values[columnIndex] = coerceForColumn(evaluator.evaluate(expression), schema.columns[columnIndex])
+                touched[columnIndex] = true
             }
-            validateNotNull(schema, values)
-            Row(values)
         }
         enforcePrimaryKeyUniqueness(schema, table.rows + newRows)
         table.rows.addAll(newRows)