Ensure casting to typmod -1 generates a RelabelType.
Fix the code changed by commit 5c056b0c2 so that we always generate
RelabelType, not something else, for a cast to unspecified typmod.
Otherwise planner optimizations might not happen.
It appears we missed this point because the previous experiments were
done on type numeric: the parser undesirably generates a call on the
numeric() length-coercion function, but then numeric_support()
optimizes that down to a RelabelType, so that everything seems fine.
It misbehaves for types that have a non-optimized length coercion
function, such as bpchar.
Per report from John Naylor. Back-patch to all supported branches,
as the previous patch eventually was. Unfortunately, that no longer
includes 9.6 ... we really shouldn't put this type of change into a
nearly-EOL branch.
Discussion: https://postgr.es/m/CAFBsxsEfbFHEkouc+FSj+3K1sHipLPbEC67L0SAe-9-da8QtYg@mail.gmail.com
Branch
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REL_12_STABLE
Details
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https://git.postgresql.org/pg/commitdiff/e1fd61c8cea76f1abca8d9a790f2188534724703
Modified Files
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src/backend/parser/parse_coerce.c | 10 ++++++++-
src/test/regress/expected/expressions.out | 36 +++++++++++++++++++++++++++++++
src/test/regress/sql/expressions.sql | 16 ++++++++++++++
3 files changed, 61 insertions(+), 1 deletion(-)
