Обсуждение: ScalarArrayOpExpr and multi-dimensional arrays

Hi.

I wonder if ScalarArrayOpExpr is not really meant for multi-dimensional
arrays appearing on the right hand side?  Because:

# select array[1] = any (array[array[1], array[2]]);

ERROR:  operator does not exist: integer[] = integer
LINE 1: select array[1] = any (array[array[1], array[2]]);
                        ^
HINT:  No operator matches the given name and argument types. You might
need to add explicit type casts.


I noticed this when looking at the constraint of a list partitioned table
on a int[] column.

create table p (a int[]) partition by list (a);
create table p1 partition of p for values in ('{1}');

\d+ p1
...
Partition of: p FOR VALUES IN ('{1}')
Partition constraint: ((a IS NOT NULL) AND ((a)::anyarray
OPERATOR(pg_catalog.=) ANY (ARRAY['{1}'::integer[]])))

I got the same error as above when I try to put that ANY expression in a
query:

select (a)::anyarray OPERATOR(pg_catalog.=) ANY (ARRAY['{1}'::integer[]])
from p;
ERROR:  operator does not exist: integer[] pg_catalog.= integer

I guess we shouldn't be generating such a constraint expression if backend
is not going to accept the same.  Or should ScalarArrayOpExpr be made to
sanely process multi-dimensional arrays appearing on the right hand side?

Thanks,
Amit

Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> writes:
> I wonder if ScalarArrayOpExpr is not really meant for multi-dimensional
> arrays appearing on the right hand side?  Because:
> # select array[1] = any (array[array[1], array[2]]);

> ERROR:  operator does not exist: integer[] = integer

You are falling into the misimpression that a 2-D array is an array of
1-D arrays.  It is not, even if the syntax makes it look like that.

ScalarArrayOpExpr just iterates over the array elements without regard
to dimensionality; so the LHS must be of the element type.

            regards, tom lane

On 2017/12/08 23:34, Tom Lane wrote:
> Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> writes:
>> I wonder if ScalarArrayOpExpr is not really meant for multi-dimensional
>> arrays appearing on the right hand side?  Because:
>> # select array[1] = any (array[array[1], array[2]]);
> 
>> ERROR:  operator does not exist: integer[] = integer
> 
> You are falling into the misimpression that a 2-D array is an array of
> 1-D arrays.  It is not, even if the syntax makes it look like that.
> 
> ScalarArrayOpExpr just iterates over the array elements without regard
> to dimensionality; so the LHS must be of the element type.

Yeah, I can now see that.

Although, I wonder if there is any room for improvement here.  Instead of
waiting for make_scalar_array_op() to emit the error as it does today,
would it be better if we error'd out earlier saying "ERROR: ANY/ALL
leftarg must be scalar, not array"?  Attached a patch for that, if it's
worth going for at all.

Thanks,
Amit