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https://issues.apache.org/jira/browse/CALCITE-4427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17244895#comment-17244895
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Julian Hyde commented on CALCITE-4427:
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This is going to be a breaking change (albeit minor):
* In 1.26, {{SUBSTRING('abcde' FROM -4 FOR 2)}} returned 'bc' (behavior
compatible with BigQuery)
* In 1.27, {{SUBSTRING('abcde' FROM -4 FOR 2)}} will return 'ab' (behavior
compatible with ISO standard SQL and PostgreSQL)
In 1.27, you will be able to override the default by setting
'semantics=bigquery' in the connect-string parameters. This will restore 1.26
behavior.
*Rationale*: Calcite always aims to be compatible with (or a superset of) ISO
standard SQL. We made a mistake in introducing non-standard behavior in
CALCITE-2572.
Also in this change, there will be {{SUBSTR}} functions compatible with
BigQuery, Oracle, MySQL, PostgreSQL. These functions all have slightly
different semantics. Whether a {{SUBSTR}} function is available, and what are
its semantics, depends on the value of the {{fun}} connect-string parameter of
that connection.
Depending on the combination of {{semantics}} and {{fun}} parameters,
{{SUBSTRING}} and {{SUBSTR}} with the same parameters may give different
results.
*Rationale*: Given that {{SUBSTRING}} is standard, and present in all dialects,
it seemed unwise to change its behavior based on the {{fun}} parameter. The new
{{semantics}} parameter was added to control it.
If people have objections to the above described behavior, please speak up very
soon.
> Make SUBSTRING operator comply with ISO standard SQL
> ----------------------------------------------------
>
> Key: CALCITE-4427
> URL: https://issues.apache.org/jira/browse/CALCITE-4427
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Priority: Major
>
> Make {{SUBSTRING}} operator comply with ISO standard SQL. It currently
> complies with BigQuery standard SQL, which gives different behavior when
> start is negative. See discussion in CALCITE-4408.
> Add an option to get the BigQuery behavior, for those who want it.
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