[GitHub] incubator-hivemall issue #58: [WIP][HIVEMALL-24] Scalable field-aware factor...

[takuti <gi...@git.apache.org>]

Github user takuti commented on the issue:

    https://github.com/apache/incubator-hivemall/pull/58
  
    ### feature_pairs()
    
    ```sql
    drop temporary function if exists feature_pairs;
    create temporary function feature_pairs as 'hivemall.ftvec.pairing.FeaturePairsUDTF';
    
    select
      t1.rowid,
      t2.i,
      t2.j,
      t2.Xi,
      t2.Xj
    from (
      select 1 as rowid, array("1:3:1", "1:11:2", "2:14:3", "3:19:4") as features
    ) t1
    LATERAL VIEW feature_pairs(features, "-ffm -feature_hashing 10 -num_fields 5") t2 as i, j, Xi, Xj;
    ```
    
    Output:
    
    ```
    t1.rowid        t2.i    t2.j    t2.xi   t2.xj
    1       0       NULL    NULL    NULL
    1       0       NULL    1.0     NULL
    1       16      56      1.0     2.0
    1       17      71      1.0     3.0
    1       18      96      1.0     4.0
    1       1       NULL    2.0     NULL
    1       57      71      2.0     3.0
    1       58      96      2.0     4.0
    1       2       NULL    3.0     NULL
    1       73      97      3.0     4.0
    1       3       NULL    4.0     NULL
    ```
    
    Todo:
    
    - Support a case that `field` is not specified e.g., `11:2`


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