Difference between CAST(v AS t) and v::t
Hi all,
while writing test cases for my SQL pretty printer tool[1]https://github.com/lelit/pg_query, I found what seems
a discrepancy in the "Type Casts" documentation[2]https://www.postgresql.org/docs/10/static/sql-expressions.html#SQL-SYNTAX-TYPE-CASTS -- nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia. lele@metapensiero.it | -- Fortunato Depero, 1929.: it states that the two
syntaxes are equivalent, but while
CREATE TABLE contracts (
...
company_id uuid NOT NULL,
validity daterange NOT NULL,
EXCLUDE USING gist (CAST(company_id AS text) WITH =, validity WITH &&)
)
works, the following
CREATE TABLE contracts (
...
company_id uuid NOT NULL,
validity daterange NOT NULL,
EXCLUDE USING gist (company_id::text WITH =, validity WITH &&)
)
is rejected with the message "syntax error at or near "::"".
Am I misreading the documentation, or is it missing some special case?
Thanks in advance for any explanation,
ciao, lele.
[1]: https://github.com/lelit/pg_query
[2]: https://www.postgresql.org/docs/10/static/sql-expressions.html#SQL-SYNTAX-TYPE-CASTS -- nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia. lele@metapensiero.it | -- Fortunato Depero, 1929.
--
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it | -- Fortunato Depero, 1929.
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Lele Gaifax <lele@metapensiero.it> writes:
while writing test cases for my SQL pretty printer tool[1], I found what seems
a discrepancy in the "Type Casts" documentation[2]: it states that the two
syntaxes are equivalent, but while
They are functionally equivalent ...
EXCLUDE USING gist (CAST(company_id AS text) WITH =, validity WITH &&)
works, the following
EXCLUDE USING gist (company_id::text WITH =, validity WITH &&)
is rejected with the message "syntax error at or near "::"".
... but expression-index syntax has the restriction that you need
parentheses around an expression unless it is, or at least looks like,
a function call. CAST() looks enough like a function call for this
purpose, v::t does not.
I think there is relevant documentation for this near CREATE INDEX;
it doesn't seem like the province of the typecast docs to explain
the weirdnesses of index syntax.
regards, tom lane
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Tom Lane <tgl@sss.pgh.pa.us> writes:
... but expression-index syntax has the restriction that you need
parentheses around an expression unless it is, or at least looks like,
a function call. CAST() looks enough like a function call for this
purpose, v::t does not.I think there is relevant documentation for this near CREATE INDEX;
it doesn't seem like the province of the typecast docs to explain
the weirdnesses of index syntax.
Thank you Tom, I really missed the explanation in CREATE INDEX doc entry!
ciao, lele.
--
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it | -- Fortunato Depero, 1929.
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