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