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Thread: [HACKERS] fix empty array expression in get_qual_for_list()

[HACKERS] fix empty array expression in get_qual_for_list()

From
Jeevan Ladhe
Date:
Hi,

In case of list partitioned table:
1. If there is a partition accepting only null values and nothing else, then
currently the partition constraints for such a partition are constructed as
"((a IS NULL) OR (a = ANY (ARRAY[]::integer[])))".
I think there it is better to avoid constructing an empty array to avoid
executing ANY expression.

2.Also, we are constructing an expression using index 0 of arrays in
PartitionKey since currently we have only one column for list partition in key,
added an assert for this.

PFA.

Regards,
Jeevan Ladhe
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Re: [HACKERS] fix empty array expression in get_qual_for_list()

From
Jeevan Ladhe
Date:
Here is an example:

create table t1 ( a int) partition by list (a);
create table t11 partition of t1 for values in (null);

Current constraints:
postgres=# \d+ t11;
                                    Table "public.t11"
 Column |  Type   | Collation | Nullable | Default | Storage | Stats target | Description 
--------+---------+-----------+----------+---------+---------+--------------+-------------
 a      | integer |           |          |         | plain   |              | 
Partition of: t1 FOR VALUES IN (NULL)
Partition constraint: ((a IS NULL) OR (a = ANY (ARRAY[]::integer[])))

Constraints after fix:
postgres=# \d+ t11;
                                    Table "public.t11"
 Column |  Type   | Collation | Nullable | Default | Storage | Stats target | Description 
--------+---------+-----------+----------+---------+---------+--------------+-------------
 a      | integer |           |          |         | plain   |              | 
Partition of: t1 FOR VALUES IN (NULL)
Partition constraint: (a IS NULL)


Regards,
Jeevan Ladhe

On Mon, Jun 26, 2017 at 4:53 PM, Jeevan Ladhe <jeevan.ladhe@enterprisedb.com> wrote:
Hi,

In case of list partitioned table:
1. If there is a partition accepting only null values and nothing else, then
currently the partition constraints for such a partition are constructed as
"((a IS NULL) OR (a = ANY (ARRAY[]::integer[])))".
I think there it is better to avoid constructing an empty array to avoid
executing ANY expression.

2.Also, we are constructing an expression using index 0 of arrays in
PartitionKey since currently we have only one column for list partition in key,
added an assert for this.

PFA.

Regards,
Jeevan Ladhe

Re: [HACKERS] fix empty array expression in get_qual_for_list()

From
Tom Lane
Date:
Jeevan Ladhe <jeevan.ladhe@enterprisedb.com> writes:
> In case of list partitioned table:
> 1. If there is a partition accepting only null values and nothing else, then
> currently the partition constraints for such a partition are constructed as
> "((a IS NULL) OR (a = ANY (ARRAY[]::integer[])))".
> I think there it is better to avoid constructing an empty array to avoid
> executing ANY expression.

Looks like a good idea, pushed with trivial stylistic adjustments.
        regards, tom lane

Re: [HACKERS] fix empty array expression in get_qual_for_list()

From
Jeevan Ladhe
Date:
On Mon, Jun 26, 2017 at 8:14 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Jeevan Ladhe <jeevan.ladhe@enterprisedb.com> writes:
> In case of list partitioned table:
> 1. If there is a partition accepting only null values and nothing else, then
> currently the partition constraints for such a partition are constructed as
> "((a IS NULL) OR (a = ANY (ARRAY[]::integer[])))".
> I think there it is better to avoid constructing an empty array to avoid
> executing ANY expression.

Looks like a good idea, pushed with trivial stylistic adjustments.
 
Thanks Tom for taking care of this.


Regards,
Jeevan Ladhe