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From "Namit Jain (JIRA)" <>
Subject [jira] Commented: (HIVE-1642) Convert join queries to map-join based on size of table/row
Date Mon, 15 Nov 2010 21:56:14 GMT


Namit Jain commented on HIVE-1642:

come more minor comments:

1203           //Qualify the path against the filesystem. The user configured path might co?
ntain default port which is skipped
1204	    //in the file status. This makes sure that all paths which goes into PathToP?
artitionInfo are always listed status
1205	    //filepath.
1206	    newPath = fs.makeQualified(newPath);

ExecDriver: is the above intentional ?

  public static String genMapJoinLocalWork(MapredWork newWork, MapJoinOperator mapJoinOp,

Make it private -- add more comments
Add more comments to the new functions

      // keep record all the input path for this alias
      HashSet<String> pathSet = new HashSet<String>();
      for (Map.Entry<String, ArrayList<String>> entry2 : pathToAliases.entrySet())
        String path = entry2.getKey();
        ArrayList<String> list = entry2.getValue();
        if (list.contains(alias)) {
          // add to path set
          if (!pathSet.contains(path)) {
          // remove this alias from the alias list

Don't you need to remove the entry from pathToAliases if list becomes empty.

> Convert join queries to map-join based on size of table/row
> -----------------------------------------------------------
>                 Key: HIVE-1642
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Liyin Tang
>             Fix For: 0.7.0
>         Attachments: hive_1642_1.patch
> Based on the number of rows and size of each table, Hive should automatically be able
to convert a join into map-join.

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