[ 
https://issues.apache.org/jira/browse/ARROW-1780?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16434167#comment-16434167
 ] 

ASF GitHub Bot commented on ARROW-1780:
---------------------------------------

laurentgo commented on a change in pull request #1759: ARROW-1780 - [WIP] JDBC 
Adapter to convert Relational Data objects to Arrow Data Format Vector Objects
URL: https://github.com/apache/arrow/pull/1759#discussion_r180815237
 
 

 ##########
 File path: 
java/adapter/jdbc/src/main/java/org/apache/arrow/adapter/jdbc/JdbcToArrowUtils.java
 ##########
 @@ -0,0 +1,431 @@
+/**
+ * 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.
+ */
+
+package org.apache.arrow.adapter.jdbc;
+
+
+import com.google.common.base.Preconditions;
+import org.apache.arrow.vector.BaseFixedWidthVector;
+import org.apache.arrow.vector.BigIntVector;
+import org.apache.arrow.vector.BitVector;
+import org.apache.arrow.vector.DateMilliVector;
+import org.apache.arrow.vector.DecimalVector;
+import org.apache.arrow.vector.FieldVector;
+import org.apache.arrow.vector.Float4Vector;
+import org.apache.arrow.vector.Float8Vector;
+import org.apache.arrow.vector.IntVector;
+import org.apache.arrow.vector.SmallIntVector;
+import org.apache.arrow.vector.TimeMilliVector;
+import org.apache.arrow.vector.TimeStampVector;
+import org.apache.arrow.vector.TinyIntVector;
+import org.apache.arrow.vector.VarBinaryVector;
+import org.apache.arrow.vector.VarCharVector;
+import org.apache.arrow.vector.VectorSchemaRoot;
+import org.apache.arrow.vector.types.DateUnit;
+import org.apache.arrow.vector.types.TimeUnit;
+import org.apache.arrow.vector.types.pojo.ArrowType;
+import org.apache.arrow.vector.types.pojo.Field;
+import org.apache.arrow.vector.types.pojo.FieldType;
+import org.apache.arrow.vector.types.pojo.Schema;
+
+import java.math.BigDecimal;
+
+import java.nio.charset.StandardCharsets;
+import java.sql.Blob;
+import java.sql.Clob;
+import java.sql.Date;
+import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
+import java.sql.SQLException;
+import java.sql.Time;
+import java.sql.Timestamp;
+import java.sql.Types;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.apache.arrow.vector.types.FloatingPointPrecision.DOUBLE;
+import static org.apache.arrow.vector.types.FloatingPointPrecision.SINGLE;
+
+
+/**
+ * Class that does most of the work to convert JDBC ResultSet data into Arrow 
columnar format Vector objects.
+ *
+ * @since 0.10.0
+ */
+public class JdbcToArrowUtils {
+
+    private static final int DEFAULT_BUFFER_SIZE = 256;
+
+    /**
+     * Create Arrow {@link Schema} object for the given JDBC {@link 
ResultSetMetaData}.
+     *
+     * This method currently performs following type mapping for JDBC SQL data 
types to corresponding Arrow data types.
+     *
+     * CHAR    --> ArrowType.Utf8
+     * NCHAR   --> ArrowType.Utf8
+     * VARCHAR --> ArrowType.Utf8
+     * NVARCHAR --> ArrowType.Utf8
+     * LONGVARCHAR --> ArrowType.Utf8
+     * LONGNVARCHAR --> ArrowType.Utf8
+     * NUMERIC --> ArrowType.Decimal(precision, scale)
+     * DECIMAL --> ArrowType.Decimal(precision, scale)
+     * BIT --> ArrowType.Bool
+     * TINYINT --> ArrowType.Int(8, signed)
+     * SMALLINT --> ArrowType.Int(16, signed)
+     * INTEGER --> ArrowType.Int(32, signed)
+     * BIGINT --> ArrowType.Int(64, signed)
+     * REAL --> ArrowType.FloatingPoint(FloatingPointPrecision.SINGLE)
+     * FLOAT --> ArrowType.FloatingPoint(FloatingPointPrecision.SINGLE)
+     * DOUBLE --> ArrowType.FloatingPoint(FloatingPointPrecision.DOUBLE)
+     * BINARY --> ArrowType.Binary
+     * VARBINARY --> ArrowType.Binary
+     * LONGVARBINARY --> ArrowType.Binary
+     * DATE --> ArrowType.Date(DateUnit.MILLISECOND)
+     * TIME --> ArrowType.Time(TimeUnit.MILLISECOND, 32)
+     * TIMESTAMP --> ArrowType.Timestamp(TimeUnit.MILLISECOND, timezone=null)
+     * CLOB --> ArrowType.Utf8
+     * BLOB --> ArrowType.Binary
+     *
+     * @param rsmd
+     * @return {@link Schema}
+     * @throws SQLException
+     */
+    public static Schema jdbcToArrowSchema(ResultSetMetaData rsmd) throws 
SQLException {
+
+        Preconditions.checkNotNull(rsmd, "JDBC ResultSetMetaData object can't 
be null");
+
+        List<Field> fields = new ArrayList<>();
+        int columnCount = rsmd.getColumnCount();
+        for (int i = 1; i <= columnCount; i++) {
+            String columnName = rsmd.getColumnName(i);
+            switch (rsmd.getColumnType(i)) {
+                case Types.BOOLEAN:
+                case Types.BIT:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Bool()), null));
+                    break;
+                case Types.TINYINT:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Int(8, true)), null));
+                    break;
+                case Types.SMALLINT:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Int(16, true)), null));
+                    break;
+                case Types.INTEGER:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Int(32, true)), null));
+                    break;
+                case Types.BIGINT:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Int(64, true)), null));
+                    break;
+                case Types.NUMERIC:
+                case Types.DECIMAL:
+                    int precision = rsmd.getPrecision(i);
+                    int scale = rsmd.getScale(i);
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Decimal(precision, scale)), null));
+                    break;
+                case Types.REAL:
+                case Types.FLOAT:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.FloatingPoint(SINGLE)), null));
+                    break;
+                case Types.DOUBLE:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.FloatingPoint(DOUBLE)), null));
+                    break;
+                case Types.CHAR:
+                case Types.NCHAR:
+                case Types.VARCHAR:
+                case Types.NVARCHAR:
+                case Types.LONGVARCHAR:
+                case Types.LONGNVARCHAR:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Utf8()), null));
+                    break;
+                case Types.DATE:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Date(DateUnit.MILLISECOND)), null));
+                    break;
+                case Types.TIME:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Time(TimeUnit.MILLISECOND, 32)), null));
+                    break;
+                case Types.TIMESTAMP:
+                    // TODO Need to handle timezone
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Timestamp(TimeUnit.MILLISECOND, null)), null));
+                    break;
+                case Types.BINARY:
+                case Types.VARBINARY:
+                case Types.LONGVARBINARY:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Binary()), null));
+                    break;
+                case Types.ARRAY:
+                    // TODO Need to handle this type
+//                    fields.add(new Field("list", FieldType.nullable(new 
ArrowType.List()), null));
+                   break;
+                case Types.CLOB:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Utf8()), null));
+                    break;
+                case Types.BLOB:
+                    fields.add(new Field(columnName, FieldType.nullable(new 
ArrowType.Binary()), null));
+                    break;
+
+                default:
+                    // no-op, shouldn't get here
+                    break;
+            }
+        }
+
+        return new Schema(fields, null);
+    }
+
+    private static void allocateVectors(VectorSchemaRoot root, int size) {
+        List<FieldVector> vectors = root.getFieldVectors();
+        for (FieldVector fieldVector: vectors) {
+            if (fieldVector instanceof BaseFixedWidthVector) {
+                ((BaseFixedWidthVector) fieldVector).allocateNew(size);
+            } else {
+                fieldVector.allocateNew();
+            }
+            fieldVector.setInitialCapacity(size);
+        }
+    }
+
+    /**
+     * Iterate the given JDBC {@link ResultSet} object to fetch the data and 
transpose it to populate
+     * the given Arrow Vector objects.
+     *
+     * @param rs ResultSet to use to fetch the data from underlying database
+     * @param root Arrow {@link VectorSchemaRoot} object to populate
+     * @throws Exception
+     */
+    public static void jdbcToArrowVectors(ResultSet rs, VectorSchemaRoot root) 
throws SQLException {
+
+        Preconditions.checkNotNull(rs, "JDBC ResultSet object can't be null");
+        Preconditions.checkNotNull(root, "JDBC ResultSet object can't be 
null");
+
+        ResultSetMetaData rsmd = rs.getMetaData();
+        int columnCount = rsmd.getColumnCount();
+
+        allocateVectors(root, DEFAULT_BUFFER_SIZE);
+
+        int rowCount = 0;
+        while (rs.next()) {
+            // for each column get the value based on the type
+
+            // need to change this to build Java lists and then build Arrow 
vectors
+            for (int i = 1; i <= columnCount; i++) {
+                String columnName = rsmd.getColumnName(i);
+                switch (rsmd.getColumnType(i)) {
+                    case Types.BOOLEAN:
+                    case Types.BIT:
+                        updateVector((BitVector)root.getVector(columnName),
+                                rs.getBoolean(i), rowCount);
+                        break;
+                    case Types.TINYINT:
+                        updateVector((TinyIntVector)root.getVector(columnName),
+                                rs.getInt(i), rowCount);
+                        break;
+                    case Types.SMALLINT:
+                        
updateVector((SmallIntVector)root.getVector(columnName),
+                                rs.getInt(i), rowCount);
+                        break;
+                    case Types.INTEGER:
+                        updateVector((IntVector)root.getVector(columnName),
+                                rs.getInt(i), rowCount);
+                        break;
+                    case Types.BIGINT:
+                        updateVector((BigIntVector)root.getVector(columnName),
+                                rs.getInt(i), rowCount);
+                        break;
+                    case Types.NUMERIC:
+                    case Types.DECIMAL:
+                        updateVector((DecimalVector)root.getVector(columnName),
+                                rs.getBigDecimal(i), rowCount);
+                        break;
+                    case Types.REAL:
+                    case Types.FLOAT:
+                        updateVector((Float4Vector)root.getVector(columnName),
+                                rs.getFloat(i), rowCount);
+                        break;
+                    case Types.DOUBLE:
+                        updateVector((Float8Vector)root.getVector(columnName),
+                                rs.getDouble(i), rowCount);
+                        break;
+                    case Types.CHAR:
+                    case Types.NCHAR:
+                    case Types.VARCHAR:
+                    case Types.NVARCHAR:
+                    case Types.LONGVARCHAR:
+                    case Types.LONGNVARCHAR:
+                        updateVector((VarCharVector)root.getVector(columnName),
+                                rs.getString(i), rowCount);
+                        break;
+                    case Types.DATE:
+                        updateVector((DateMilliVector) 
root.getVector(columnName),
+                                rs.getDate(i), rowCount);
+                        break;
+                    case Types.TIME:
+                        updateVector((TimeMilliVector) 
root.getVector(columnName),
+                                rs.getTime(i), rowCount);
+                        break;
+                    case Types.TIMESTAMP:
+                        
updateVector((TimeStampVector)root.getVector(columnName),
+                                rs.getTimestamp(i), rowCount);
+                        break;
+                    case Types.BINARY:
+                    case Types.VARBINARY:
+                    case Types.LONGVARBINARY:
+                        
updateVector((VarBinaryVector)root.getVector(columnName),
+                                rs.getBytes(i), rowCount);
+                        break;
+                    case Types.ARRAY:
+                        // TODO Need to handle this type
+//                    fields.add(new Field("list", FieldType.nullable(new 
ArrowType.List()), null));
+                        break;
+                    case Types.CLOB:
+                        updateVector((VarCharVector)root.getVector(columnName),
+                            rs.getClob(i), rowCount);
+                        break;
+                    case Types.BLOB:
+                        
updateVector((VarBinaryVector)root.getVector(columnName),
+                            rs.getBlob(i), rowCount);
+                        break;
+
+                    default:
+                        // no-op, shouldn't get here
+                        break;
+                }
+            }
+            rowCount++;
+        }
+        root.setRowCount(rowCount);
+    }
+
+    private static void updateVector(BitVector bitVector, boolean value, int 
rowCount) {
 
 Review comment:
   still not sure how null values are handled...

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> JDBC Adapter for Apache Arrow
> -----------------------------
>
>                 Key: ARROW-1780
>                 URL: https://issues.apache.org/jira/browse/ARROW-1780
>             Project: Apache Arrow
>          Issue Type: New Feature
>            Reporter: Atul Dambalkar
>            Assignee: Atul Dambalkar
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 0.10.0
>
>
> At a high level the JDBC Adapter will allow upstream apps to query RDBMS data 
> over JDBC and get the JDBC objects converted to Arrow objects/structures. The 
> upstream utility can then work with Arrow objects/structures with usual 
> performance benefits. The utility will be very much similar to C++ 
> implementation of "Convert a vector of row-wise data into an Arrow table" as 
> described here - 
> https://arrow.apache.org/docs/cpp/md_tutorials_row_wise_conversion.html
> The utility will read data from RDBMS and covert the data into Arrow 
> objects/structures. So from that perspective this will Read data from RDBMS, 
> If the utility can push Arrow objects to RDBMS is something need to be 
> discussed and will be out of scope for this utility for now. 



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