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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-6965) Adjust table function usage for all storage plugins and implement schema parameter
Date Wed, 01 May 2019 14:34:00 GMT

    [ https://issues.apache.org/jira/browse/DRILL-6965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16831026#comment-16831026

ASF GitHub Bot commented on DRILL-6965:

arina-ielchiieva commented on issue #1777: DRILL-6965: Implement schema table function parameter
URL: https://github.com/apache/drill/pull/1777#issuecomment-488298669
   @vvysotskyi please review.
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> Adjust table function usage for all storage plugins and implement schema parameter
> ----------------------------------------------------------------------------------
>                 Key: DRILL-6965
>                 URL: https://issues.apache.org/jira/browse/DRILL-6965
>             Project: Apache Drill
>          Issue Type: Sub-task
>            Reporter: Arina Ielchiieva
>            Assignee: Arina Ielchiieva
>            Priority: Major
>              Labels: doc-impacting
>             Fix For: 1.17.0
> Schema can be used while reading the table into two ways:
> a. schema is created in the table root folder using CREATE SCHEMA command and schema
usage command is enabled;
> b. schema indicated in table function.
> This Jira implements point b.
> Schema indication using table function is useful when user does not want to persist schema
in table root location or when reading from file, not folder.
> Schema parameter can be used as individual unit or in together with for format plugin
table properties.
> Usage examples:
> Pre-requisites: 
> V3 reader must be enabled: {{set `exec.storage.enable_v3_text_reader` = true;}}
> Query examples:
> 1. There is folder with files or just one file (ex: dfs.tmp.text_table) and user wants
to apply schema to them:
> a. indicate schema inline:
> {noformat}
> select * from table(dfs.tmp.`text_table`(schema => 'inline=(col1 date properties {`drill.format`
= `yyyy-MM-dd`} properties {`drill.strict` = `false`})'))
> {noformat}
> b. indicate schema using path:
> First schema was created in some location using CREATE SCHEMA command. For example:
> {noformat}
> create schema 
> (col int)
> path '/tmp/my_schema'
> {noformat}
> Now user wants to apply this schema in table function:
> {noformat}
> select * from table(dfs.tmp.`text_table`(schema => 'path=`/tmp/my_schema`'))
> {noformat}
> 2. User want to apply schema along side with format plugin table function parameters.
> Assume user has CSV file with headers with extension that does not comply to default
text file with headers extension (ex: cars.csvh-test):
> {noformat}
> select * from table(dfs.tmp.`cars.csvh-test`(type => 'text', fieldDelimiter =>
',', extractHeader => true, schema => 'inline=(col1 date)'))
> {noformat}
> More details about syntax can be found in design document:
> https://docs.google.com/document/d/1mp4egSbNs8jFYRbPVbm_l0Y5GjH3HnoqCmOpMTR_g4w/edit

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