Github user jihoonson commented on the pull request:
https://github.com/apache/tajo/pull/231#issuecomment-62916612
This is a result of performance test.
* Data: synthetic data
* Size: 74.4GB
* # of rows: 357913940
* DDL
* create external table gen2 (id int4, sel_0_001 int4, sel_0_01 int4,
sel_0_1 int4, sel_1 int4, sel_5 int4, sel_10 int4, sel_20 int4, f1 text, f2
text, f3 text, f4 text, f5 text, f6 text, f7 text, f8 text, f9 text, f10 text,
f11 text, pad text) USING CSV WITH ('csvfile.delimiter'=',') LOCATION
'/gen/50g_2';
* The sel_0_001, sel_0_01, sel_0_1, sel_1, sel_5, sel_10, and sel_20
columns have 0.001, 0.01, 0.1, 1, 5, 10, and 20% selectivities, respectively.
* Query: select id from gen2 where $col = 1;
* $col: sel_0_001, sel_0_01, sel_0_1, sel_1, sel_5, sel_10, sel_20
* Result
* Creation time (sec)
| Index name | Time |
|:-------------:|:-------------:|
|sel_0_001|159.237|
|sel_0_01|137.716|
|sel_0_1|135.772|
|sel_1|121.511|
|sel_5|124.585|
|sel_10|123.593|
|sel_20|120.621|
* Query execution time (sec)
| $col | Seq scan | Index scan |
|:-------------:|:-------------:|:-------------:|
|sel_0_001|8.445|67.681|
|sel_0_01|16.306|75.628|
|sel_0_1|54.602|74.602|
|sel_1|98.552|78.056|
|sel_5|104.018|69.755|
|sel_10|117.401|81.483|
|sel_20|103.993|71.334|
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