On Sat, 13 Nov 2021 at 23:42, Tom Lane <t...@sss.pgh.pa.us> wrote: > Japin Li <japi...@hotmail.com> 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 -- Regrads, Japin Li. ChengDu WenWu Information Technology Co.,Ltd.
