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https://issues.apache.org/jira/browse/FLINK-26945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17703975#comment-17703975
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jackylau commented on FLINK-26945:
----------------------------------
hi [~twalthr] , thanks, i know what does the conversionClass means now. it can
using conversionClass(bridgedTo) to converter to the java class
internal/external of DateType.
DataTypes.DATE().notNull().bridgedTo(int.class)` -> it will to external int
instead of LocalDatetime (DateType default conversion class).
for example String input type, so the cast logical will
# StringToDateCast (string -> int)
# internal to External (int to int) DataStructureConverter.
{code:java}
// code placeholder
castEvaluator =
context.createEvaluator(
$("startDate").cast(DataTypes.DATE().notNull()),
DataTypes.DATE().notNull(),
DataTypes.FIELD("startDate",
startDate.notNull().toInternal())); {code}
> Add DATE_SUB supported in SQL & Table API
> -----------------------------------------
>
> Key: FLINK-26945
> URL: https://issues.apache.org/jira/browse/FLINK-26945
> Project: Flink
> Issue Type: Sub-task
> Components: Table SQL / API
> Reporter: dalongliu
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.17.0
>
>
> Returns the date {{numDays}} before {{{}startDate{}}}.
> Syntax:
> {code:java}
> date_sub(startDate, numDays) {code}
> Arguments:
> * {{{}startDate{}}}: A DATE expression.
> * {{{}numDays{}}}: An INTEGER expression.
> Returns:
> A DATE.
> If {{numDays}} is negative abs(num_days) are added to {{{}startDate{}}}.
> If the result date overflows the date range the function raises an error.
> Examples:
> {code:java}
> > SELECT date_sub('2016-07-30', 1);
> 2016-07-29 {code}
> See more:
> *
> [Spark|https://spark.apache.org/docs/latest/sql-ref-functions-builtin.html#date-and-timestamp-functions]
> * [Hive|https://cwiki.apache.org/confluence/display/hive/languagemanual+udf]
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