Fix fb_reshape_row for ArrayType equal comparisom (facebookincubator#…

…11169)

Summary:

fb_reshape_row returns wrong result for array of row when "from" and "to" row types are the same size and same type but different names.

For example:
```
SELECT
    fb_reshape_row(
        col,
        CAST(NULL AS ROW(arr ARRAY(ROW(b VARCHAR, a VARCHAR))))
    ) as col
FROM (
    SELECT CAST(ROW(x) AS ROW(arr ARRAY(ROW(a VARCHAR, b VARCHAR)))) AS col
    FROM (
    VALUES 
        (ARRAY[('1', '2')])
    ) t(x)
);
```

In fb_reshape_row::reshapeRow, if it finds fromType is equal to toType, it will not do transformation
```
if (fromVector->type()->asRow().equals(toType->asRow())) {
      return fromVector;
    }
```

For `RowType::equals` comparison, it will iterate its children and apply `operator==` for equal comparison.
However `operator==`  is not defined for ArrayType and the equal logic fall back to use ArrayType::equivalent which is weakly matched.

Differential Revision: D63883106

velox/type/Type.cpp

@@ -233,6 +233,17 @@ const TypePtr& ArrayType::childAt(uint32_t idx) const {
 ArrayType::ArrayType(TypePtr child)
     : child_{std::move(child)}, parameters_{{TypeParameter(child_)}} {}
 
+bool ArrayType::operator==(const Type& other) const {
+  if (&other == this) {
+    return true;
+  }
+  if (!Type::hasSameTypeId(other)) {
+    return false;
+  }
+  auto& otherArray = other.asArray();
+  return *child_ == (*otherArray.child_);
+}
+
 bool ArrayType::equivalent(const Type& other) const {
   if (&other == this) {
     return true;

velox/type/Type.h

@@ -905,6 +905,8 @@ class ArrayType : public TypeBase<TypeKind::ARRAY> {
 
   std::string toString() const override;
 
+  bool operator==(const Type& other) const override;
+
   bool equivalent(const Type& other) const override;
 
   folly::dynamic serialize() const override;

velox/type/tests/TypeTest.cpp

@@ -663,9 +663,6 @@ TEST(TypeTest, equality) {
   EXPECT_FALSE(
       *ROW({{"a", ROW({{"x", INTEGER()}, {"y", INTEGER()}})}}) ==
       *ROW({{"a", ROW({{"x", INTEGER()}, {"z", INTEGER()}})}}));
-  EXPECT_FALSE(
-      *ROW({{"a", ROW({{"x", INTEGER()}, {"y", INTEGER()}})}}) ==
-      *ARRAY(INTEGER()));
 
   // mix
   EXPECT_FALSE(MAP(REAL(), INTEGER())