On Sun, Nov 14, 2021 at 10:33:19AM +0800, Japin Li wrote:
>
> On Sat, 13 Nov 2021 at 23:42, Tom Lane <[email protected]> wrote:
> > Japin Li <[email protected]> writes:
> >> postgres=# CREATE TABLE tbl (s varchar(2147483647));
> >> ERROR: length for type varchar cannot exceed 10485760
> >> LINE 1: CREATE TABLE tbl (s varchar(2147483647));
> >> ^
> >
> >> postgres=# CREATE TABLE tbl (s varchar(2147483648));
> >> ERROR: syntax error at or near "2147483648"
> >> LINE 1: CREATE TABLE tbl (s varchar(2147483648));
> >> ^
> >
> > I'm having a very hard time getting excited about that. We could maybe
> > switch the grammar production to use generic expr_list syntax for the
> > typmod, like GenericType does. But that would just result in this:
> >
> > regression=# CREATE TABLE tbl (s "varchar"(2147483648));
> > ERROR: value "2147483648" is out of range for type integer
> > LINE 1: CREATE TABLE tbl (s "varchar"(2147483648));
> > ^
> >
> > which doesn't seem any less confusing for a novice who doesn't know
> > that typmods are constrained to be integers.
> >
> > There might be something to be said for switching all the hard-wired
> > type productions to use opt_type_modifiers and pushing the knowledge
> > that's in, eg, opt_float out to per-type typmodin routines. But any
> > benefit would be in reduction of the grammar size, and I'm dubious
> > that it'd be worth the trouble. I suspect that overall, the resulting
> > error messages would be slightly worse not better --- note for example
> > the poorer placement of the error cursor above. A related example is
> >
> > regression=# CREATE TABLE tbl (s varchar(2,3));
> > ERROR: syntax error at or near ","
> > LINE 1: CREATE TABLE tbl (s varchar(2,3));
> > ^
> > regression=# CREATE TABLE tbl (s "varchar"(2,3));
> > ERROR: invalid type modifier
> > LINE 1: CREATE TABLE tbl (s "varchar"(2,3));
> > ^
> >
> > That's explained by the comment in anychar_typmodin:
> >
> > * we're not too tense about good error message here because grammar
> > * shouldn't allow wrong number of modifiers for CHAR
> >
> > and we could surely improve that message, but anychar_typmodin can't give
> > a really on-point error cursor.
> >
>
> Oh! I didn't consider this situation. Since the max size of varchar cannot
> exceed 10485760, however, I cannot find this in documentation [1]. Is there
> something I missed? Should we mention this in the documentation?
>
> [1] https://www.postgresql.org/docs/devel/datatype-character.html
Sorry for my long delay in reviewing this issue. You are correct this
should be documented --- patch attached.
--
Bruce Momjian <[email protected]> https://momjian.us
EDB https://enterprisedb.com
Indecision is a decision. Inaction is an action. Mark Batterson
diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index 4cc9e59270..07c3654b21 100644
--- a/doc/src/sgml/datatype.sgml
+++ b/doc/src/sgml/datatype.sgml
@@ -1217,6 +1217,8 @@ SELECT '52093.89'::money::numeric::float8;
<type>char(<replaceable>n</replaceable>)</type> are aliases for <type>character
varying(<replaceable>n</replaceable>)</type> and
<type>character(<replaceable>n</replaceable>)</type>, respectively.
+ The length specification must be greater than zero and cannot
+ exceed 10485760.
<type>character</type> without length specifier is equivalent to
<type>character(1)</type>. If <type>character varying</type> is used
without length specifier, the type accepts strings of any size. The
