Distinct Throw exception java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

[KomachiSion]

Bug Report

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

Which version of ShardingSphere did you use?

4.0.0-RC2

Which project did you use? Sharding-JDBC or Sharding-Proxy?

Sharding-Proxy

Expected behavior

execute SQL select distinct(user_id) from t_order success

Actual behavior

[ERROR] 10:06:09.837 [ShardingSphere-Command-4] o.a.s.s.f.c.CommandExecutorTask - Exception occur: 
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
	at java.util.ArrayList.rangeCheck(ArrayList.java:657)
	at java.util.ArrayList.get(ArrayList.java:433)
	at org.apache.shardingsphere.core.execute.sql.execute.result.DistinctQueryResult.getColumnIndex(DistinctQueryResult.java:208)
	at org.apache.shardingsphere.core.execute.sql.execute.result.DistinctQueryResult$1.apply(DistinctQueryResult.java:95)
	at org.apache.shardingsphere.core.execute.sql.execute.result.DistinctQueryResult$1.apply(DistinctQueryResult.java:91)
	at com.google.common.collect.Lists$TransformingRandomAccessList$1.transform(Lists.java:617)
	at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:48)
	at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:48)
	at java.util.AbstractList.hashCode(AbstractList.java:540)
	at org.apache.shardingsphere.core.execute.sql.execute.row.QueryRow.hashCode(QueryRow.java:84)
	at java.util.HashMap.hash(HashMap.java:339)
	at java.util.HashMap.put(HashMap.java:612)
	at java.util.HashSet.add(HashSet.java:220)
	at org.apache.shardingsphere.core.execute.sql.execute.result.DistinctQueryResult.fill(DistinctQueryResult.java:111)
	at org.apache.shardingsphere.core.execute.sql.execute.result.DistinctQueryResult.getResultData(DistinctQueryResult.java:99)
	at org.apache.shardingsphere.core.execute.sql.execute.result.DistinctQueryResult.<init>(DistinctQueryResult.java:67)
	at org.apache.shardingsphere.core.merge.dql.DQLMergeEngine.getRealQueryResults(DQLMergeEngine.java:85)
	at org.apache.shardingsphere.core.merge.dql.DQLMergeEngine.<init>(DQLMergeEngine.java:71)
	at org.apache.shardingsphere.core.merge.MergeEngineFactory.newInstance(MergeEngineFactory.java:58)
	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.JDBCDatabaseCommunicationEngine.merge(JDBCDatabaseCommunicationEngine.java:110)
	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.JDBCDatabaseCommunicationEngine.execute(JDBCDatabaseCommunicationEngine.java:95)
	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.JDBCDatabaseCommunicationEngine.execute(JDBCDatabaseCommunicationEngine.java:77)
	at org.apache.shardingsphere.shardingproxy.backend.text.query.QueryBackendHandler.execute(QueryBackendHandler.java:54)
	at org.apache.shardingsphere.shardingproxy.frontend.mysql.command.query.text.query.MySQLComQueryPacketExecutor.execute(MySQLComQueryPacketExecutor.java:72)
	at org.apache.shardingsphere.shardingproxy.frontend.command.CommandExecutorTask.executeCommand(CommandExecutorTask.java:86)
	at org.apache.shardingsphere.shardingproxy.frontend.command.CommandExecutorTask.run(CommandExecutorTask.java:66)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

Reason analyze (If you can)

The input distinctColumnLabels in DistinctQueryResult is (user_id), but columnLabel in ResultSet and columnLabelAndIndexMap is user_id, so can find this columnLabel.

distinctColumnLabels is come from ShardingSelectOptimizedStatement, so there may be mistakes in Optimize.

Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc.

sharding rule configuration:

schemaName: sharding_db

dataSources:
  ds_0:
    url: jdbc:mysql://127.0.0.1:3306/demo_ds_0?serverTimezone=UTC&useSSL=false
    username: root
    password:
    connectionTimeoutMilliseconds: 30000
    idleTimeoutMilliseconds: 60000
    maxLifetimeMilliseconds: 1800000
    maxPoolSize: 50
  ds_1:
    url: jdbc:mysql://127.0.0.1:3306/demo_ds_1?serverTimezone=UTC&useSSL=false
    username: root
    password:
    connectionTimeoutMilliseconds: 30000
    idleTimeoutMilliseconds: 60000
    maxLifetimeMilliseconds: 1800000
    maxPoolSize: 50

shardingRule:
  tables:
    t_order:
      actualDataNodes: ds_${0..1}.t_order_${0..1}
      tableStrategy:
        inline:
          shardingColumn: order_id
          algorithmExpression: t_order_${order_id % 2}
      keyGenerator:
        type: SNOWFLAKE
        column: order_id
    t_order_item:
      actualDataNodes: ds_${0..1}.t_order_item_${0..1}
      tableStrategy:
        inline:
          shardingColumn: order_id
          algorithmExpression: t_order_item_${order_id % 2}
      keyGenerator:
        type: SNOWFLAKE
        column: order_item_id
  bindingTables:
    - t_order,t_order_item
  defaultDatabaseStrategy:
    inline:
      shardingColumn: user_id
      algorithmExpression: ds_${user_id % 2}
  defaultTableStrategy:
    none:

SQL:

CREATE TABLE IF NOT EXISTS t_order (order_id BIGINT AUTO_INCREMENT, user_id INT NOT NULL, status VARCHAR(50), PRIMARY KEY (order_id));

CREATE TABLE IF NOT EXISTS t_order_item (order_item_id BIGINT AUTO_INCREMENT, order_id BIGINT, user_id INT NOT NULL, status VARCHAR(50) , PRIMARY KEY (order_item_id), KEY order_id(order_id));

select distinct(user_id) from t_order

Example codes for reproduce this issue (such as a github link).

[jasonlong10]

version 3.1.0 also has this bug. Can it fixed in 3.x.x?