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https://issues.apache.org/jira/browse/ARROW-1780?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16423125#comment-16423125
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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_r178648346
##########
File path:
java/adapter/jdbc/src/main/java/org/apache/arrow/adapter/jdbc/ArrowDataFetcher.java
##########
@@ -0,0 +1,107 @@
+/**
+ * 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 org.apache.arrow.vector.VectorSchemaRoot;
+
+import java.sql.Connection;
+
+/**
+ * Class to fetch data from a given database table where user can specify
columns to fetch
+ * along with limit and offset parameters.
+ *
+ * The object of this class is returned by invoking method
jdbcArrowDataFetcher(Connection connection, String tableName)
+ * from {@link JdbcToArrow} class. Caller can use this object to fetch data
repetitively based on the
+ * data fetch requirement and can implement pagination like functionality.
+ *
+ * This class doesn't hold any open connections to database but simply
executes the "select" query everytime with
+ * the necessary limit and offset parameters.
+ *
+ * @since 0.10.0
+ * @see JdbcToArrow
+ */
+public class ArrowDataFetcher {
+
+ private static final String all_columns_query = "select * from %s limit %d
offset %d";
+ private static final String custom_columns_query = "select %s from %s
limit %d offset %d";
+ private Connection connection;
+ private String tableName;
+
+ /**
+ * Constructor
+ * @param connection
+ * @param tableName
+ */
+ public ArrowDataFetcher(Connection connection, String tableName) {
Review comment:
That's my belief too...
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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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