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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-3572) Support FETCH NEXT| n ROWS from Cursor
Date Mon, 13 Feb 2017 07:54:41 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-3572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15863300#comment-15863300
] 

ASF GitHub Bot commented on PHOENIX-3572:
-----------------------------------------

Github user ankitsinghal commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/229#discussion_r100738871
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/util/CursorUtil.java ---
    @@ -0,0 +1,203 @@
    +/*
    + * 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.phoenix.util;
    +
    +import java.sql.Connection;
    +import java.sql.SQLException;
    +import java.util.HashMap;
    +import java.util.Map;
    +
    +import org.apache.hadoop.hbase.client.Scan;
    +import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
    +import org.apache.phoenix.compile.QueryPlan;
    +import org.apache.phoenix.compile.OrderByCompiler.OrderBy;
    +import org.apache.phoenix.execute.CursorFetchPlan;
    +import org.apache.phoenix.iterate.CursorResultIterator;
    +import org.apache.phoenix.parse.CloseStatement;
    +import org.apache.phoenix.parse.DeclareCursorStatement;
    +import org.apache.phoenix.parse.OpenStatement;
    +import org.apache.phoenix.schema.tuple.Tuple;
    +
    +public final class CursorUtil {
    +
    +    private static class CursorWrapper {
    +        private final String cursorName;
    +        private final String selectSQL;
    +        private boolean isOpen = false;
    +        QueryPlan queryPlan;
    +        ImmutableBytesWritable row;
    +        ImmutableBytesWritable previousRow;
    +        private Scan scan;
    +        private boolean moreValues=true;
    +        private boolean isReversed;
    +        private boolean islastCallNext;
    +        private CursorFetchPlan fetchPlan;
    +        private int offset = -1;
    +
    +        private CursorWrapper(String cursorName, String selectSQL, QueryPlan queryPlan){
    +            this.cursorName = cursorName;
    +            this.selectSQL = selectSQL;
    +            this.queryPlan = queryPlan;
    +            this.islastCallNext = true;
    +            this.fetchPlan = new CursorFetchPlan(queryPlan);
    +        }
    +
    +        private synchronized void openCursor(Connection conn) throws SQLException {
    +            if(isOpen){
    +                return;
    +            }
    +            this.scan = this.queryPlan.getContext().getScan();
    +            isReversed=OrderBy.REV_ROW_KEY_ORDER_BY.equals(this.queryPlan.getOrderBy());
    +            isOpen = true;
    +        }
    +
    +        private void closeCursor() throws SQLException {
    +            isOpen = false;
    +            ((CursorResultIterator) fetchPlan.iterator()).closeCursor();
    +            //TODO: Determine if the cursor should be removed from the HashMap at this
point.
    +            //Semantically it makes sense that something which is 'Closed' one should
be able to 'Open' again.
    +            mapCursorIDQuery.remove(this.cursorName);
    +        }
    +
    +        private QueryPlan getFetchPlan(boolean isNext, int fetchSize) throws SQLException
{
    +            if (!isOpen)
    +                throw new SQLException("Fetch call on closed cursor '" + this.cursorName
+ "'!");
    +            ((CursorResultIterator)fetchPlan.iterator()).setFetchSize(fetchSize);
    +            if (!queryPlan.getStatement().isAggregate() || !queryPlan.getStatement().isDistinct())
{ 
    +            	if (islastCallNext != isNext) {
    +                    if (islastCallNext && !isReversed){
    +                       ScanUtil.setReversed(scan);
    +                } else {
    +                       ScanUtil.unsetReversed(scan);
    +                }
    --- End diff --
    
    this code seems to be for reverse/prior and belongs to another JIRA. can we remove this
if it can affect the functionality?


> Support FETCH NEXT| n ROWS from Cursor
> --------------------------------------
>
>                 Key: PHOENIX-3572
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-3572
>             Project: Phoenix
>          Issue Type: Sub-task
>            Reporter: Biju Nair
>            Assignee: Biju Nair
>
> Implement required changes to support 
> - {{DECLARE}} and {{OPEN}} a cursor
> - query {{FETCH NEXT | n ROWS}} from the cursor
> - {{CLOSE}} the cursor
> Based on the feedback in [PR #192|https://github.com/apache/phoenix/pull/192], implement
the changes using {{ResultSet}}.



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