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From "DaeMyung Kang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (TAJO-122) Add EXPLAIN clause to show a logical plan
Date Sat, 11 Jan 2014 16:17:53 GMT

     [ https://issues.apache.org/jira/browse/TAJO-122?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

DaeMyung Kang updated TAJO-122:
-------------------------------

    Attachment: TAJO-122.patch

Explain works like this.

{noformat}
//valid query
tajo> explain select * from table1;

-----------------------------
Query Block Graph
-----------------------------
|-@ROOT
-----------------------------
Optimization Log:
-----------------------------

Scan on table1
  => target list: table1.id (INT4(0)), table1.name (TEXT(0)), table1.score (FLOAT4(0)),
table1.type (TEXT(0))
  => out schema: {table1.id (INT4(0)),table1.name (TEXT(0)),table1.score (FLOAT4(0)),table1.type
(TEXT(0))}
  => in schema: {table1.id (INT4(0)),table1.name (TEXT(0)),table1.score (FLOAT4(0)),table1.type
(TEXT(0))}

//invalid query because of not existed table
tajo> explain select * from tbl;
Failed after attempts=3, exceptions:
org.apache.tajo.catalog.exception.NoSuchTableException: ERROR: relation "tbl" does not exist
org.apache.tajo.catalog.exception.NoSuchTableException: ERROR: relation "tbl" does not exist
org.apache.tajo.catalog.exception.NoSuchTableException: ERROR: relation "tbl" does not exist

//valid but doesn't have logical plan.
tajo> explain select pi();

-----------------------------
Query Block Graph
-----------------------------
|-@ROOT
-----------------------------
Optimization Log:
-----------------------------
{noformat}

> Add EXPLAIN clause to show a logical plan
> -----------------------------------------
>
>                 Key: TAJO-122
>                 URL: https://issues.apache.org/jira/browse/TAJO-122
>             Project: Tajo
>          Issue Type: New Feature
>          Components: planner/optimizer
>            Reporter: Hyunsik Choi
>            Assignee: DaeMyung Kang
>             Fix For: 0.8-incubating
>
>         Attachments: TAJO-122.patch
>
>
> (I've changed this issue from implementing an utility class to preint JSON to implementing
EXPLAIN clause support.)
> For convenience for debugging and developing new engine (TAJO-104), we need EXPLAIN clause
to print plans used in Tajo internal. In this issue, we only focus on showing a logical plan.



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