Peter Eisentraut <peter_e@gmx.net> writes:
> Note that varchar mostly "borrows" the cast functions from the text type. The
> exception is that there is a separate set of SQL-level functions for casting
> between name and varchar and vice versa. But these are actually matched to
> the same C-level functions as the casts between text and name (name_text()
> and text_name()).
> Does anyone recall a reason for this special case or is it just another dark
> area in the casting maze?
I think the idea was to support the functional casting notation, viz
"varchar(name_col)". However it seems we've broken that already for
most of the other cases; and in any case it never worked very nicely
for varchar because "varchar" is a reserved word, so you have to
quote :-(
As a historical note, in 7.3 (the first release with a pg_cast catalog)
your query gives just
castsource | casttarget | castfunc | castcontext
-------------------+-------------------+-------------------------+-------------name | character varying |
"varchar"(name) | itext | character varying | - | icharacter |
charactervarying | - | icharacter varying | name | name(character varying) |
icharactervarying | text | - | icharacter varying | character | -
| i
(6 rows)
So it seems the cross-category casts for varchar got accreted on later,
rather than it being a case of things having disappeared.
regards, tom lane
