release-2.1: sql: Fix the handling of NULL arguments in string_agg #30076
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Prior to this patch, if you called `string_agg(x, delim)` with a NULL delimiter, the results were incorrect, as it should behave exactly like `concat_agg(x)` or even `string_agg(x, '')`. This updated behaviour now matches Postgres'. See the list of new test cases for a more complete list of examples. This also required adding checking to in distsql for both aggregate and window functions to allow matching ambiguous results only when the aggregate function accepts null arguments. The string_agg algorithm was also cleaned up and its memory counting was tightened. Release note (sql bug fix): string_agg() can now accept a NULL as a delimiter.
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jordanlewis
approved these changes
Sep 11, 2018
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TFTR! |
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Backport 1/1 commits from #29652.
/cc @cockroachdb/release
Prior to this patch, if you called
string_agg(x, delim)with a NULL delimiter,the results were incorrect, as it should behave exactly like
concat_agg(x)oreven
string_agg(x, ''). This updated behaviour now matches Postgres'.See the list of new test cases for a more complete list of examples.
This also required adding checking to in distsql for both aggregate and window
functions to allow matching ambiguous results only when the aggregate function
accepts null arguments.
The string_agg algorithm was also cleaned up and its memory counting was
tightened.
Release note (sql bug fix): string_agg() can now accept a NULL as a delimiter.