Fix dremel assembly

src/assemble.js

@@ -49,13 +49,21 @@ export function assembleObjects(
 
     // Add value or null based on definition level
     if (def === maxDefinitionLevel) {
+      if (!currentContainer) {
+        throw new Error('parquet assembleObjects: currentContainer is undefined')
+      }
       currentContainer.push(values[valueIndex++])
-    } else if (isNull && def < maxDefinitionLevel) {
-      // Go up one level to add null
+    } else if (isNull) {
       if (def) {
-        containerStack.pop()
-        // @ts-expect-error won't be empty
-        currentContainer = containerStack.at(-1)
+        // TODO: Go up maxDefinitionLevel - def - 1 levels to add null
+        for (let j = def; j < maxDefinitionLevel - 1; j++) {
+          containerStack.pop()
+          // @ts-expect-error won't be empty
+          currentContainer = containerStack.at(-1)
+        }
+        if (def > 1) {
+          currentContainer.push(undefined)
+        }
       } else {
         currentContainer.push(undefined)
       }

test/assemble.test.js

@@ -83,9 +83,25 @@ describe('assembleObjects', () => {
     expect(result).toEqual([[[]]])
   })
 
-  it('should handle isNull correctly', () => {
+  it('should handle isNull', () => {
     // from nonnullable.impala.parquet
     const result = assembleObjects([2], [0], [-1], false, 2, 2)
     expect(result).toEqual([[[-1]]])
   })
+
+  it('should handle nullable int_array', () => {
+    // from nullable.impala.parquet
+    //                       [1  2  3][N  1  2  N  3  N][ ] N  N
+    const definitionLevels = [3, 3, 3, 2, 3, 3, 2, 3, 2, 1, 0, 0]
+    const repetitionLevels = [0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 0]
+    const values = [1, 2, 3, 1, 2, 3]
+    const result = assembleObjects(definitionLevels, repetitionLevels, values, true, 3, 1)
+    expect(result).toEqual([
+      [1, 2, 3],
+      [undefined, 1, 2, undefined, 3, undefined],
+      [],
+      undefined,
+      undefined,
+    ])
+  })
 })