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ARROW-92: Arrow to Parquet Schema conversion #68

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ARROW-92: Arrow to Parquet Schema conversion #68

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8a0293e
ARROW-92: Arrow to Parquet Schema conversion
xhochy Apr 24, 2016
9a6c876
Add more types
xhochy May 1, 2016
38e68e5
make format
xhochy May 1, 2016
42ed0ea
Add struct conversion
xhochy May 1, 2016
9c5b085
Include string
xhochy May 1, 2016
e3aa261
Add macro to convert ParquetException to Status
xhochy May 1, 2016
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75 changes: 75 additions & 0 deletions cpp/src/arrow/parquet/parquet-schema-test.cc
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Expand Up @@ -161,6 +161,81 @@ TEST_F(TestConvertParquetSchema, UnsupportedThings) {
}
}

class TestConvertArrowSchema : public ::testing::Test {
public:
virtual void SetUp() {}

void CheckFlatSchema(const std::vector<NodePtr>& nodes) {
NodePtr schema_node = GroupNode::Make("schema", Repetition::REPEATED, nodes);
const GroupNode* expected_schema_node =
static_cast<const GroupNode*>(schema_node.get());
const GroupNode* result_schema_node =
static_cast<const GroupNode*>(result_schema_->schema().get());

ASSERT_EQ(expected_schema_node->field_count(), result_schema_node->field_count());

for (int i = 0; i < expected_schema_node->field_count(); i++) {
auto lhs = result_schema_node->field(i);
auto rhs = expected_schema_node->field(i);
EXPECT_TRUE(lhs->Equals(rhs.get()));
}
}

Status ConvertSchema(const std::vector<std::shared_ptr<Field>>& fields) {
arrow_schema_ = std::make_shared<Schema>(fields);
return ToParquetSchema(arrow_schema_.get(), &result_schema_);
}

protected:
std::shared_ptr<Schema> arrow_schema_;
std::shared_ptr<::parquet::SchemaDescriptor> result_schema_;
};

TEST_F(TestConvertArrowSchema, ParquetFlatPrimitives) {
std::vector<NodePtr> parquet_fields;
std::vector<std::shared_ptr<Field>> arrow_fields;

parquet_fields.push_back(
PrimitiveNode::Make("boolean", Repetition::REQUIRED, ParquetType::BOOLEAN));
arrow_fields.push_back(std::make_shared<Field>("boolean", BOOL, false));

parquet_fields.push_back(
PrimitiveNode::Make("int32", Repetition::REQUIRED, ParquetType::INT32));
arrow_fields.push_back(std::make_shared<Field>("int32", INT32, false));

parquet_fields.push_back(
PrimitiveNode::Make("int64", Repetition::REQUIRED, ParquetType::INT64));
arrow_fields.push_back(std::make_shared<Field>("int64", INT64, false));

parquet_fields.push_back(
PrimitiveNode::Make("float", Repetition::OPTIONAL, ParquetType::FLOAT));
arrow_fields.push_back(std::make_shared<Field>("float", FLOAT));

parquet_fields.push_back(
PrimitiveNode::Make("double", Repetition::OPTIONAL, ParquetType::DOUBLE));
arrow_fields.push_back(std::make_shared<Field>("double", DOUBLE));

// TODO: String types need to be clarified a bit more in the Arrow spec
parquet_fields.push_back(PrimitiveNode::Make(
"string", Repetition::OPTIONAL, ParquetType::BYTE_ARRAY, LogicalType::UTF8));
arrow_fields.push_back(std::make_shared<Field>("string", UTF8));

ASSERT_OK(ConvertSchema(arrow_fields));

CheckFlatSchema(parquet_fields);
}

TEST_F(TestConvertArrowSchema, ParquetFlatDecimals) {
std::vector<NodePtr> parquet_fields;
std::vector<std::shared_ptr<Field>> arrow_fields;

// TODO: Test Decimal Arrow -> Parquet conversion

ASSERT_OK(ConvertSchema(arrow_fields));

CheckFlatSchema(parquet_fields);
}

TEST(TestNodeConversion, DateAndTime) {}

} // namespace parquet
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123 changes: 123 additions & 0 deletions cpp/src/arrow/parquet/schema.cc
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Expand Up @@ -17,13 +17,16 @@

#include "arrow/parquet/schema.h"

#include <string>
#include <vector>

#include "parquet/api/schema.h"

#include "arrow/types/decimal.h"
#include "arrow/types/string.h"
#include "arrow/util/status.h"

using parquet::Repetition;
using parquet::schema::Node;
using parquet::schema::NodePtr;
using parquet::schema::GroupNode;
Expand Down Expand Up @@ -182,6 +185,126 @@ Status FromParquetSchema(
return Status::OK();
}

Status StructToNode(const std::shared_ptr<StructType>& type, const std::string& name,
bool nullable, NodePtr* out) {
Repetition::type repetition = Repetition::REQUIRED;
if (nullable) { repetition = Repetition::OPTIONAL; }

std::vector<NodePtr> children(type->num_children());
for (int i = 0; i < type->num_children(); i++) {
RETURN_NOT_OK(FieldToNode(type->child(i), &children[i]));
}

*out = GroupNode::Make(name, repetition, children);
return Status::OK();
}

Status FieldToNode(const std::shared_ptr<Field>& field, NodePtr* out) {
LogicalType::type logical_type = LogicalType::NONE;
ParquetType::type type;
Repetition::type repetition = Repetition::REQUIRED;
if (field->nullable) { repetition = Repetition::OPTIONAL; }
int length = -1;

switch (field->type->type) {
// TODO:
// case Type::NA:
// break;
case Type::BOOL:
type = ParquetType::BOOLEAN;
break;
case Type::UINT8:
type = ParquetType::INT32;
logical_type = LogicalType::UINT_8;
break;
case Type::INT8:
type = ParquetType::INT32;
logical_type = LogicalType::INT_8;
break;
case Type::UINT16:
type = ParquetType::INT32;
logical_type = LogicalType::UINT_16;
break;
case Type::INT16:
type = ParquetType::INT32;
logical_type = LogicalType::INT_16;
break;
case Type::UINT32:
type = ParquetType::INT32;
logical_type = LogicalType::UINT_32;
break;
case Type::INT32:
type = ParquetType::INT32;
break;
case Type::UINT64:
type = ParquetType::INT64;
logical_type = LogicalType::UINT_64;
break;
case Type::INT64:
type = ParquetType::INT64;
break;
case Type::FLOAT:
type = ParquetType::FLOAT;
break;
case Type::DOUBLE:
type = ParquetType::DOUBLE;
break;
case Type::CHAR:
type = ParquetType::FIXED_LEN_BYTE_ARRAY;
logical_type = LogicalType::UTF8;
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@wesm wesm May 1, 2016 •
edited
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Aside: we'll need to visit the string encoding question, as logical unicode characters won't map neatly onto a char(n) type

length = static_cast<CharType*>(field->type.get())->size;
break;
case Type::STRING:
type = ParquetType::BYTE_ARRAY;
logical_type = LogicalType::UTF8;
break;
case Type::BINARY:
type = ParquetType::BYTE_ARRAY;
break;
case Type::DATE:
type = ParquetType::INT32;
logical_type = LogicalType::DATE;
break;
case Type::TIMESTAMP:
type = ParquetType::INT64;
logical_type = LogicalType::TIMESTAMP_MILLIS;
break;
case Type::TIMESTAMP_DOUBLE:
type = ParquetType::INT64;
// This is specified as seconds since the UNIX epoch
// TODO: Converted type in Parquet?
// logical_type = LogicalType::TIMESTAMP_MILLIS;
break;
case Type::TIME:
type = ParquetType::INT64;
logical_type = LogicalType::TIME_MILLIS;
break;
case Type::STRUCT: {
auto struct_type = std::static_pointer_cast<StructType>(field->type);
return StructToNode(struct_type, field->name, field->nullable, out);
} break;
default:
// TODO: LIST, DENSE_UNION, SPARE_UNION, JSON_SCALAR, DECIMAL, DECIMAL_TEXT, VARCHAR
return Status::NotImplemented("unhandled type");
}
*out = PrimitiveNode::Make(field->name, repetition, type, logical_type, length);
return Status::OK();
}

Status ToParquetSchema(
const Schema* arrow_schema, std::shared_ptr<::parquet::SchemaDescriptor>* out) {
std::vector<NodePtr> nodes(arrow_schema->num_fields());
for (int i = 0; i < arrow_schema->num_fields(); i++) {
RETURN_NOT_OK(FieldToNode(arrow_schema->field(i), &nodes[i]));
}

NodePtr schema = GroupNode::Make("schema", Repetition::REPEATED, nodes);
*out = std::make_shared<::parquet::SchemaDescriptor>();
(*out)->Init(schema);
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Init can throw an exception. We will need some macro to convert ParquetException into an arrow::Status

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As we cannot distinguish why a ParquetException was thrown, I just mapped all to Status::Invalid.

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We'll probably need to add Status type for "thirdparty exceptions".


return Status::OK();
}

} // namespace parquet

} // namespace arrow
5 changes: 5 additions & 0 deletions cpp/src/arrow/parquet/schema.h
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Expand Up @@ -36,6 +36,11 @@ Status NodeToField(const ::parquet::schema::NodePtr& node, std::shared_ptr<Field
Status FromParquetSchema(
const ::parquet::SchemaDescriptor* parquet_schema, std::shared_ptr<Schema>* out);

Status FieldToNode(const std::shared_ptr<Field>& field, ::parquet::schema::NodePtr* out);

Status ToParquetSchema(
const Schema* arrow_schema, std::shared_ptr<::parquet::SchemaDescriptor>* out);

} // namespace parquet

} // namespace arrow
Expand Down