[jira] [Created] (DRILL-6673) Drill table functions cannot use plugin configs with a constructor

["Paul Rogers (JIRA)" <ji...@apache.org>]

Paul Rogers created DRILL-6673:
----------------------------------

             Summary: Drill table functions cannot use plugin configs with a constructor
                 Key: DRILL-6673
                 URL: https://issues.apache.org/jira/browse/DRILL-6673
             Project: Apache Drill
          Issue Type: Bug
    Affects Versions: 1.13.0
            Reporter: Paul Rogers


Consider an example format plugin, such as the regex one used in the Drill book. (GitHub reference needed.) Format configurations should be immutable. So, we make the members {{private final}} and define a constructor like this:

{code}
public class RegexFormatConfig implements FormatPluginConfig {

  private final String regex;

  // Should be a List<String>. But, table functions don't support
  // lists, so we store the fields as single string that contains
  // a comma-delimited list: a, b, c. Spaces are optional.

  private final String fields;
  private final String extension;

  public RegexFormatConfig(
      @JsonProperty("extension") String extension,
      @JsonProperty("regex") String regex,
      @JsonProperty("fields") String fields
      ) {
    this.regex = regex;
    this.fields = fields;
    this.extension = extension;
  }
{code}

We can then create a plugin configuration using the Drill Web console, the {{bootstrap-storage-plugins.json}} and so on. All work fine.

Suppose we try to define a configuration using a Drill table function:

{code}
      final String sql = "SELECT * FROM table(cp.`regex/simple.log2`\n" +
          "(type => 'regex',\n" +
          " extension => 'log2',\n" +
          " regex => '(\\\\d\\\\d\\\\d\\\\d)-(\\\\d\\\\d)-(\\\\d\\\\d) .*',\n" +
          " fields => 'a, b, c, d'))";
{code}

We get this error:

{noformat}
org.apache.drill.common.exceptions.UserRemoteException: PARSE ERROR: 
configuration for format of type regex can not be created 
(class: org.apache.drill.exec.store.easy.regex.RegexFormatConfig)

table regex/simple.log2

{noformat}

They fail because the code that resolves the plugin configuration does not know about the Jackson constructor conventions: it requires an default constructor:

{code}
package org.apache.drill.exec.store.dfs;
...
final class FormatPluginOptionsDescriptor {
  ...
  FormatPluginConfig createConfigForTable(TableInstance t) {
    ...
    try {
      config = pluginConfigClass.newInstance();
    } catch (InstantiationException | IllegalAccessException e) {
      throw UserException.parseError(e)
          .message(
              "configuration for format of type %s can not be created (class: %s)",
              this.typeName, pluginConfigClass.getName())
         ...
{code}

The workaround would seem to be to define setters using Jackson standards. But, that does not work either due to DRILL-6672 which says that Drill table functions don't allow them. The only real workaround is to make the fields {{public}} and omit the constructor.



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