[GSoC] create type questions

Charles Cui <charles.cui1984@gmail.com> writes:

I have a new type defined like this
CREATE TYPE thrift_binary (
INPUT = thrift_binary_in,
OUTPUT = thrift_binary_out,
LIKE = bytea
);

in thrift_binary_in, it accepts cstring and returns thrift_binary.

OK, that's what it should do.

And in
this function I returned a bytea because the create type tells the system
thrift_binary and bytea are the same.

Sure, PG_RETURN_BYTEA_P() would work in the C code. I think it might be
worth inventing a macro PG_RETURN_THRIFT_BINARY_P that's a thin wrapper
around that, just for clarity's sake, but it doesn't matter functionally.

However, the test passes only when I
explicitly tell thrift_binary_in to return a bytea (change the return type
from thrift_binary to bytea), and it does not work when returns
thrift_binary.

What do you mean by "the test passes" (or doesn't pass)? What do you
mean by "tell thrift_binary_in to return a bytea"? You just said you
were already doing that.

This works for me:

regression=# create type thrift_binary;
CREATE TYPE
regression=# create function thrift_binary_in(cstring) returns thrift_binary
regression-# strict immutable language internal as 'byteain';
NOTICE: return type thrift_binary is only a shell
CREATE FUNCTION
regression=# create function thrift_binary_out(thrift_binary) returns cstring
regression-# strict immutable language internal as 'byteaout';
NOTICE: argument type thrift_binary is only a shell
CREATE FUNCTION
regression=# CREATE TYPE thrift_binary (
regression(# INPUT = thrift_binary_in,
regression(# OUTPUT = thrift_binary_out,
regression(# LIKE = bytea
regression(# );
CREATE TYPE

I cheated here by pointing to byteain/byteaout instead of C functions
that'd actually do what you want, but CREATE TYPE doesn't know that.

I suspect you may have forgotten the initial dummy creation of
thrift_binary as a "shell type".

regards, tom lane

Hi Tom,

Thanks for your comments, I do forget create type shell.
But even if I add this line still does not work.
Here is the commit that can demo my bug (
https://github.com/charles-cui/pg_thrift/commit/8b43f3e2172f4a1b4e61211f7d76b061a90c38f7
)
To see it, download the repo and do make install && make installcheck.
It cannot return a bytea as expected.

Thanks Charles!

2018-06-01 18:28 GMT-07:00 Tom Lane <tgl@sss.pgh.pa.us>:

"Charles" == Charles Cui <charles.cui1984@gmail.com> writes:

Charles> Hi Tom,
Charles> Thanks for your comments, I do forget create type shell.
Charles> But even if I add this line still does not work.
Charles> Here is the commit that can demo my bug (
Charles> https://github.com/charles-cui/pg_thrift/commit/8b43f3e2172f4a1b4e61211f7d76b061a90c38f7
Charles> )
Charles> To see it, download the repo and do make install && make installcheck.
Charles> It cannot return a bytea as expected.

Your output function isn't doing anything, and in particular it's not
returning any value (just dropping off the end), so as soon as pg tries
to output a query result containing a thrift_binary value, it either
outputs garbage or crashes.

--
Andrew (irc:RhodiumToad)

Thanks Andrew, that should be the reason!
Forget thrift_binary_in is not a simple function, it is always coupled with
output function.

2018-06-02 10:44 GMT-07:00 Andrew Gierth <andrew@tao11.riddles.org.uk>: