ARROW-24: C++: Implement a logical Table container type

A table enables us to interpret a collection of Arrow arrays as a logical table or "data frame"-like structure.  Each column may consist of one or more "primitive" Arrow memory containers.

Note that this currently has the limitation that the table column names must be strings. At least, this is consistent with most storage media and up-stack table implementations (e.g. R's data.frame).

Currently this is somewhat limited in the arrangement of data (a vector of chunked columns -- the columns may contain only one data chunk) -- since a Table might be assembled from a vector of row batches (coming across the wire), "pivoting" the row batches might have performance implications that we can examine further on down the road.

Author: Wes McKinney <wesm@apache.org>

Closes #16 from wesm/ARROW-24 and squashes the following commits:

b701c76 [Wes McKinney] Test case for wrong number of columns passed
5faa5ac [Wes McKinney] cpplint
9a651cb [Wes McKinney] Basic table prototype. Move Schema code under arrow/table

Author: wesm

cpp/CMakeLists.txt

@@ -470,7 +470,6 @@ set(ARROW_SRCS
   src/arrow/array.cc
   src/arrow/builder.cc
   src/arrow/field.cc
-  src/arrow/schema.cc
   src/arrow/type.cc
 )
 

cpp/src/arrow/CMakeLists.txt

@@ -30,4 +30,3 @@ install(FILES
 set(ARROW_TEST_LINK_LIBS arrow_test_util ${ARROW_MIN_TEST_LIBS})
 
 ADD_ARROW_TEST(array-test)
-ADD_ARROW_TEST(schema-test)

cpp/src/arrow/table/CMakeLists.txt

@@ -21,6 +21,8 @@
 
 set(TABLE_SRCS
   column.cc
+  schema.cc
+  table.cc
 )
 
 set(TABLE_LIBS
@@ -37,3 +39,5 @@ install(FILES
   DESTINATION include/arrow/table)
 
 ADD_ARROW_TEST(column-test)
+ADD_ARROW_TEST(schema-test)
+ADD_ARROW_TEST(table-test)

cpp/src/arrow/table/column-test.cc

@@ -22,48 +22,29 @@
 #include <vector>
 
 #include "arrow/field.h"
-#include "arrow/schema.h"
 #include "arrow/table/column.h"
+#include "arrow/table/schema.h"
+#include "arrow/table/test-common.h"
 #include "arrow/test-util.h"
 #include "arrow/type.h"
 #include "arrow/types/integer.h"
-#include "arrow/util/bit-util.h"
-#include "arrow/util/buffer.h"
-#include "arrow/util/memory-pool.h"
-#include "arrow/util/status.h"
 
 using std::shared_ptr;
 using std::vector;
 
 namespace arrow {
 
-class TestColumn : public ::testing::Test {
- public:
-  void SetUp() {
-    pool_ = GetDefaultMemoryPool();
-  }
-
-  template <typename ArrayType>
-  std::shared_ptr<Array> MakeArray(int32_t length, int32_t null_count = 0) {
-    auto data = std::make_shared<PoolBuffer>(pool_);
-    auto nulls = std::make_shared<PoolBuffer>(pool_);
-    data->Resize(length * sizeof(typename ArrayType::value_type));
-    nulls->Resize(util::bytes_for_bits(length));
-    return std::make_shared<ArrayType>(length, data, 10, nulls);
-  }
-
+class TestColumn : public TestBase {
  protected:
-  MemoryPool* pool_;
-
   std::shared_ptr<ChunkedArray> data_;
   std::unique_ptr<Column> column_;
 };
 
 TEST_F(TestColumn, BasicAPI) {
   ArrayVector arrays;
-  arrays.push_back(MakeArray<Int32Array>(100));
-  arrays.push_back(MakeArray<Int32Array>(100, 10));
-  arrays.push_back(MakeArray<Int32Array>(100, 20));
+  arrays.push_back(MakePrimitive<Int32Array>(100));
+  arrays.push_back(MakePrimitive<Int32Array>(100, 10));
+  arrays.push_back(MakePrimitive<Int32Array>(100, 20));
 
   auto field = std::make_shared<Field>("c0", INT32);
   column_.reset(new Column(field, arrays));
@@ -77,15 +58,15 @@ TEST_F(TestColumn, BasicAPI) {
 
 TEST_F(TestColumn, ChunksInhomogeneous) {
   ArrayVector arrays;
-  arrays.push_back(MakeArray<Int32Array>(100));
-  arrays.push_back(MakeArray<Int32Array>(100, 10));
+  arrays.push_back(MakePrimitive<Int32Array>(100));
+  arrays.push_back(MakePrimitive<Int32Array>(100, 10));
 
   auto field = std::make_shared<Field>("c0", INT32);
   column_.reset(new Column(field, arrays));
 
   ASSERT_OK(column_->ValidateData());
 
-  arrays.push_back(MakeArray<Int16Array>(100, 10));
+  arrays.push_back(MakePrimitive<Int16Array>(100, 10));
   column_.reset(new Column(field, arrays));
   ASSERT_RAISES(Invalid, column_->ValidateData());
 }

cpp/src/arrow/table/column.cc

@@ -39,6 +39,12 @@ Column::Column(const std::shared_ptr<Field>& field, const ArrayVector& chunks) :
   data_ = std::make_shared<ChunkedArray>(chunks);
 }
 
+Column::Column(const std::shared_ptr<Field>& field,
+    const std::shared_ptr<Array>& data) :
+    field_(field) {
+  data_ = std::make_shared<ChunkedArray>(ArrayVector({data}));
+}
+
 Column::Column(const std::shared_ptr<Field>& field,
     const std::shared_ptr<ChunkedArray>& data) :
     field_(field),

cpp/src/arrow/table/column.h

@@ -67,6 +67,8 @@ class Column {
   Column(const std::shared_ptr<Field>& field,
       const std::shared_ptr<ChunkedArray>& data);
 
+  Column(const std::shared_ptr<Field>& field, const std::shared_ptr<Array>& data);
+
   int64_t length() const {
     return data_->length();
   }

cpp/src/arrow/schema-test.cc cpp/src/arrow/table/schema-test.cccpp/src/arrow/schema-test.cc renamed to cpp/src/arrow/table/schema-test.cc

@@ -21,7 +21,7 @@
 #include <vector>
 
 #include "arrow/field.h"
-#include "arrow/schema.h"
+#include "arrow/table/schema.h"
 #include "arrow/type.h"
 #include "arrow/types/string.h"
 

cpp/src/arrow/schema.cc cpp/src/arrow/table/schema.cccpp/src/arrow/schema.cc renamed to cpp/src/arrow/table/schema.cc

@@ -15,7 +15,7 @@
 // specific language governing permissions and limitations
 // under the License.
 
-#include "arrow/schema.h"
+#include "arrow/table/schema.h"
 
 #include <memory>
 #include <string>

cpp/src/arrow/schema.h cpp/src/arrow/table/schema.hcpp/src/arrow/schema.h renamed to cpp/src/arrow/table/schema.h

@@ -0,0 +1,125 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <gtest/gtest.h>
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "arrow/field.h"
+#include "arrow/table/column.h"
+#include "arrow/table/schema.h"
+#include "arrow/table/table.h"
+#include "arrow/table/test-common.h"
+#include "arrow/test-util.h"
+#include "arrow/type.h"
+#include "arrow/types/integer.h"
+
+using std::shared_ptr;
+using std::vector;
+
+namespace arrow {
+
+class TestTable : public TestBase {
+ public:
+  void MakeExample1(int length) {
+    auto f0 = std::make_shared<Field>("f0", INT32);
+    auto f1 = std::make_shared<Field>("f1", UINT8);
+    auto f2 = std::make_shared<Field>("f2", INT16);
+
+    vector<shared_ptr<Field> > fields = {f0, f1, f2};
+    schema_ = std::make_shared<Schema>(fields);
+
+    columns_ = {
+      std::make_shared<Column>(schema_->field(0), MakePrimitive<Int32Array>(length)),
+      std::make_shared<Column>(schema_->field(1), MakePrimitive<UInt8Array>(length)),
+      std::make_shared<Column>(schema_->field(2), MakePrimitive<Int16Array>(length))
+    };
+  }
+
+ protected:
+  std::unique_ptr<Table> table_;
+  shared_ptr<Schema> schema_;
+  vector<std::shared_ptr<Column> > columns_;
+};
+
+TEST_F(TestTable, EmptySchema) {
+  auto empty_schema = shared_ptr<Schema>(new Schema({}));
+  table_.reset(new Table("data", empty_schema, columns_));
+  ASSERT_OK(table_->ValidateColumns());
+  ASSERT_EQ(0, table_->num_rows());
+  ASSERT_EQ(0, table_->num_columns());
+}
+
+TEST_F(TestTable, Ctors) {
+  int length = 100;
+  MakeExample1(length);
+
+  std::string name = "data";
+
+  table_.reset(new Table(name, schema_, columns_));
+  ASSERT_OK(table_->ValidateColumns());
+  ASSERT_EQ(name, table_->name());
+  ASSERT_EQ(length, table_->num_rows());
+  ASSERT_EQ(3, table_->num_columns());
+
+  table_.reset(new Table(name, schema_, columns_, length));
+  ASSERT_OK(table_->ValidateColumns());
+  ASSERT_EQ(name, table_->name());
+  ASSERT_EQ(length, table_->num_rows());
+}
+
+TEST_F(TestTable, Metadata) {
+  int length = 100;
+  MakeExample1(length);
+
+  std::string name = "data";
+  table_.reset(new Table(name, schema_, columns_));
+
+  ASSERT_TRUE(table_->schema()->Equals(schema_));
+
+  auto col = table_->column(0);
+  ASSERT_EQ(schema_->field(0)->name, col->name());
+  ASSERT_EQ(schema_->field(0)->type, col->type());
+}
+
+TEST_F(TestTable, InvalidColumns) {
+  // Check that columns are all the same length
+  int length = 100;
+  MakeExample1(length);
+
+  table_.reset(new Table("data", schema_, columns_, length - 1));
+  ASSERT_RAISES(Invalid, table_->ValidateColumns());
+
+  columns_.clear();
+
+  // Wrong number of columns
+  table_.reset(new Table("data", schema_, columns_, length));
+  ASSERT_RAISES(Invalid, table_->ValidateColumns());
+
+  columns_ = {
+    std::make_shared<Column>(schema_->field(0), MakePrimitive<Int32Array>(length)),
+    std::make_shared<Column>(schema_->field(1), MakePrimitive<UInt8Array>(length)),
+    std::make_shared<Column>(schema_->field(2), MakePrimitive<Int16Array>(length - 1))
+  };
+
+  table_.reset(new Table("data", schema_, columns_, length));
+  ASSERT_RAISES(Invalid, table_->ValidateColumns());
+}
+
+} // namespace arrow