[jira] [Commented] (DRILL-162) Implement substring function

["Tanujit Ghosh (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-162?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13729082#comment-13729082 ] 

Tanujit Ghosh commented on DRILL-162:
-------------------------------------

I tried applying the patch, but its failing

[tanujit@legolas incubator-drill]$ git apply --check substring_function.patch
error: patch failed: sandbox/prototype/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/Substring.java:1
error: sandbox/prototype/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/Substring.java: patch does not apply
error: patch failed: sandbox/prototype/exec/java-exec/src/test/java/org/apache/drill/exec/physical/impl/TestSimpleFunctions.java:182
error: sandbox/prototype/exec/java-exec/src/test/java/org/apache/drill/exec/physical/impl/TestSimpleFunctions.java: patch does not apply
error: patch failed: sandbox/prototype/exec/java-exec/src/test/java/org/apache/drill/exec/physical/impl/TestSimpleFunctions.java:185
error: sandbox/prototype/exec/java-exec/src/test/java/org/apache/drill/exec/physical/impl/TestSimpleFunctions.java: patch does not apply


I think the version of Substring.java in master is different from the one you have based the patch on

[tanujit@legolas incubator-drill]$ cat sandbox/prototype/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/Substring.java
/*******************************************************************************
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 * 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
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package org.apache.drill.exec.expr.fn.impl;

import org.apache.drill.common.expression.ArgumentValidators;
import org.apache.drill.common.expression.CallProvider;
import org.apache.drill.common.expression.FunctionDefinition;
import org.apache.drill.common.expression.OutputTypeDeterminer;
import org.apache.drill.exec.expr.DrillFunc;
import org.apache.drill.exec.expr.annotations.FunctionTemplate;
import org.apache.drill.exec.expr.annotations.Output;
import org.apache.drill.exec.expr.annotations.Param;
import org.apache.drill.exec.record.RecordBatch;
import org.apache.drill.exec.vector.*;

// TODO: implement optional length parameter
//       implement negative start position

@FunctionTemplate(name = "substring",
                  scope = FunctionTemplate.FunctionScope.SIMPLE,
                  nulls = FunctionTemplate.NullHandling.NULL_IF_NULL)
public class Substring implements DrillFunc {

  @Param VarCharHolder string;
  @Param BigIntHolder offset;
  @Param BigIntHolder length;
  @Output VarCharHolder out;

  @Override
  public void setup(RecordBatch incoming) { }

  @Override
  public void eval() {
    out.buffer = string.buffer;
    out.start = (int)offset.value;
    out.end = (int)length.value;
  }

  public static class Provider implements CallProvider {

    @Override
    public FunctionDefinition[] getFunctionDefintions() {
      return new FunctionDefinition[] {
          FunctionDefinition.simple("substring",
                                    new ArgumentValidators.AnyTypeAllowed(3),
                                    new OutputTypeDeterminer.SameAsFirstInput(),
                                    "substring",
                                    "substr")
      };
    }
  }
}


                
> Implement substring function
> ----------------------------
>
>                 Key: DRILL-162
>                 URL: https://issues.apache.org/jira/browse/DRILL-162
>             Project: Apache Drill
>          Issue Type: New Feature
>            Reporter: Ben Becker
>            Assignee: Ben Becker
>         Attachments: substring_function.patch
>
>
> Implement SUBSTRING with support for byte and character (UTF-8) sequences.
> {code}
> SUBSTRING ( expression , start, length )
> {code}
> h5. Types:
> {{expression}}: VARCHAR or VARBINARY
> {{start}}: Literal BIGINT
> {{length}}: Literal BIGINT
> {{Returns}}: Same type as the {{expression}} argument
> h5. Arguments:
> {{start}}: position within the {{expression}} value the return value will start from
> {{length}}: number of subsequent characters or bytes to return.
> h5. Aliases:
> {{SUBSTR}}
> {{BYTE_SUBSTR}}
> h5. Return Value:
> Returns the specified portion of the input string.  
> h5. Notes on behavior:
>  - If the start position is negative, start from abs(start) characters from the end of the buffer.
>  - If no length is specified, continue to the end of the string.
>  - BYTE_SUBSTR always assumes a character is 8 bits, while SUBSTR accounts for UTF-8 character sequences.
>  - If the substring expression's length exceeds the value's upward bound, the
>    value's length will be used.
>  - If the substring is invalid (e.g. negative length), return an empty string.

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