gengliangwang opened a new pull request, #37221:
URL: https://github.com/apache/spark/pull/37221
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### What changes were proposed in this pull request?
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This is a follow-up of https://github.com/apache/spark/pull/37160, which
changes the default behavior of `CAST(DECIMAL AS STRING)` as always using the
plain string representation for ANSI SQL compliance.
This PR is to move the new behavior under ANSI SQL mode. The default
behavior remains unchanged.
### Why are the changes needed?
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After offline discussions, changing the default behavior brings upgrade
risks to Spark 3.4.0.
Since the motivation for the new behaviors is ANSI SQL compliance, the new
behavior only exists in the ANSI SQL mode makes more sense.
Users who enable the ANSI SQL mode are supposed to accept such a breaking
change.
### Does this PR introduce _any_ user-facing change?
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Yes, though not released yet, this PR makes the behavior of casting decimal
values to string more reasonable by always using plain string under ANSI SQL
mode.
### How was this patch tested?
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