[DRILL-6672] Drill table functions cannot handle "setFoo" accessors

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Not A Problem
• Affects Version/s: 1.13.0
• Assignee: Paul Rogers
• Reporter: Paul Rogers
• Created: 08/Aug/18 00:22
• Updated: 12/Apr/20 00:27
• Resolved: 12/Apr/20 00:27

Description

Consider an example format plugin, such as the regex one used in the Drill book. (GitHub reference needed.) We can define the plugin using getters and setters like this:

public class RegexFormatConfig implements FormatPluginConfig {

  private String regex;
  private String fields;
  private String extension;

  public void setRegex(String regex) { this.regex = regex; }
  public void setFields(String fields) { this.fields = fields; }
  public void setExtension(String extension) { this.extension = extension; }

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:

      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'))";

We get this error:

org.apache.drill.common.exceptions.UserRemoteException: PARSE ERROR: 
can not set value (\d\d\d\d)-(\d\d)-(\d\d) .* to parameter regex: class java.lang.String

table regex/simple.log2
parameter regex

The reason is that the code that handles table functions only knows how to set public fields, it does not know about the Java Bean getter/setter conventions used by Jackson:

package org.apache.drill.exec.store.dfs;
...
final class FormatPluginOptionsDescriptor {
  ...
  FormatPluginConfig createConfigForTable(TableInstance t) {
    ...
        Field field = pluginConfigClass.getField(paramDef.name);
        ...
        }
        field.set(config, param);
      } catch (IllegalAccessException | NoSuchFieldException | SecurityException e) {
        throw UserException.parseError(e)
            .message("can not set value %s to parameter %s: %s", param, paramDef.name, paramDef.type)
            ...

The only workaround is to make all fields public:

public class RegexFormatConfig implements FormatPluginConfig {

  public String regex;
  public String fields;
  public String extension;

Since public fields are not good practice, please modify the table function mechanism to follow Jackson conventions and allow Java Bean style setters. (Or better, fix DRILL-6673 to allow immutable format objects via the use of a constructor.)

Issue Links

• Is contained by: DRILL-6986 Table function improvements / issues (UMBRELLA JIRA)
• is related to: DRILL-7612 Modify the Text, Excel format config, etc. immutable