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https://issues.apache.org/jira/browse/DRILL-6965?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arina Ielchiieva updated DRILL-6965:
------------------------------------
Description:
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
was:Design doc -
https://docs.google.com/document/d/1mp4egSbNs8jFYRbPVbm_l0Y5GjH3HnoqCmOpMTR_g4w/edit
> 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
> 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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