Thread: [HACKERS] Partitions: \d vs \d+

[HACKERS] Partitions: \d vs \d+

From

Jesper Pedersen

Date:

28 September 2017, 16:02:37

Hi,

Using hash partitions I noticed that \d gives

D=# \d T_p63               Table "public.T_p63"    Column     |     Type      | Collation | Nullable | Default
---------------+---------------+-----------+----------+---------

<remove>

Partition of: T FOR VALUES WITH (modulus 64, remainder 63)
No partition constraint
Indexes:    "T_p63" btree (X, Y)

where as \d+ gives

D=# \d+ T_p63               Table "public.T_p63"    Column     |     Type      | Collation | Nullable | Default | 
Storage  | Stats target | Description
---------------+---------------+-----------+----------+---------+----------+--------------+-------------

<remove>

Partition of: T FOR VALUES WITH (modulus 64, remainder 63)
Partition constraint: satisfies_hash_partition(64, 63, 
hashint4extended(X, '8816678312871386367'::bigint))
Indexes:    "T_p63" btree (X, Y)

E.g. "No partition constraint" vs. "Partition constraint: 
satisfies_hash_partition(...)".

Current master (7769fc000) with [1] and [2].

[1] https://commitfest.postgresql.org/14/1059/
[2] https://commitfest.postgresql.org/14/1089/

Best regards, Jesper


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Re: [HACKERS] Partitions: \d vs \d+

From

Maksim Milyutin

Date:

28 September 2017, 16:19:48

Hi!

On 28.09.2017 16:02, Jesper Pedersen wrote:

Hi,

Using hash partitions I noticed that \d gives

D=# \d T_p63
               Table "public.T_p63"
    Column     |     Type      | Collation | Nullable | Default
---------------+---------------+-----------+----------+---------

<remove>

Partition of: T FOR VALUES WITH (modulus 64, remainder 63)
No partition constraint
Indexes:
    "T_p63" btree (X, Y)

where as \d+ gives

D=# \d+ T_p63
               Table "public.T_p63"
    Column     |     Type      | Collation | Nullable | Default | Storage | Stats target | Description
---------------+---------------+-----------+----------+---------+----------+--------------+-------------

<remove>

Partition of: T FOR VALUES WITH (modulus 64, remainder 63)
Partition constraint: satisfies_hash_partition(64, 63, hashint4extended(X, '8816678312871386367'::bigint))
Indexes:
    "T_p63" btree (X, Y)

E.g. "No partition constraint" vs. "Partition constraint: satisfies_hash_partition(...)".

I also noticed ambiguity in printing "No partition constraint" in non-verbose mode and "Partition constraint:..." in verbose one for partition tables regardless of the type of partition.
Attached small patch removes any output about partition constraint in non-verbose mode.

-- 
Regards,
Maksim Milyutin

Attachment

psql_def_part_fix.patch

Re: [HACKERS] Partitions: \d vs \d+

From

Jesper Pedersen

Date:

28 September 2017, 16:29:29

On 09/28/2017 09:19 AM, Maksim Milyutin wrote:
>> E.g. "No partition constraint" vs. "Partition constraint: 
>> satisfies_hash_partition(...)".
> 
> I also noticed ambiguity in printing "No partition constraint" in 
> non-verbose mode and "Partition constraint:..." in verbose one for 
> partition tables regardless of the type of partition.
> Attached small patch removes any output about partition constraint in 
> non-verbose mode.
> 

Yeah, that could be one way.

It should likely be backported to REL_10_STABLE, so the question is if 
we are too late in the release cycle to change that output.

Best regards, Jesper


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Re: [HACKERS] Partitions: \d vs \d+

From

Maksim Milyutin

Date:

28 September 2017, 16:41:33

On 28.09.2017 16:29, Jesper Pedersen wrote:

On 09/28/2017 09:19 AM, Maksim Milyutin wrote:
E.g. "No partition constraint" vs. "Partition constraint: satisfies_hash_partition(...)".

I also noticed ambiguity in printing "No partition constraint" in non-verbose mode and "Partition constraint:..." in verbose one for partition tables regardless of the type of partition.
Attached small patch removes any output about partition constraint in non-verbose mode.

Yeah, that could be one way.

It should likely be backported to REL_10_STABLE, so the question is if we are too late in the release cycle to change that output.

I want to prepare more complete patch for "Partition constraint" output. For example, I encountered the primitive output with repetitive conjuncts for subpartition whose parent is partitioned by the same key:

Partition constraint: ((i IS NOT NULL) AND (i >= 30) AND (i < 40) AND (i IS NOT NULL) AND (i = ANY (ARRAY[30, 31])))

-- 
Regards,
Maksim Milyutin

Re: [HACKERS] Partitions: \d vs \d+

From

Amit Langote

Date:

29 September 2017, 04:23:28

On 2017/09/28 22:29, Jesper Pedersen wrote:
> On 09/28/2017 09:19 AM, Maksim Milyutin wrote:
>>> E.g. "No partition constraint" vs. "Partition constraint:
>>> satisfies_hash_partition(...)".
>>
>> I also noticed ambiguity in printing "No partition constraint" in
>> non-verbose mode and "Partition constraint:..." in verbose one for
>> partition tables regardless of the type of partition.
>> Attached small patch removes any output about partition constraint in
>> non-verbose mode.
>>
> 
> Yeah, that could be one way.
> 
> It should likely be backported to REL_10_STABLE, so the question is if we
> are too late in the release cycle to change that output.

I think the default partition commit [1] introduced some change around
that code, so the behavior is new in 11dev and I think it needs a fix like
the one that Maksim proposed.

When I check with REL_10_STABLE tip, I find things to be normal:

create table p (a int) partition by list (a);
create table p1 partition of p for values in (1);

\d p1                Table "public.p1"Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------a      | integer |           |          |
Partition of: p FOR VALUES IN (1)

\d+ p1                                   Table "public.p1"Column |  Type   | Collation | Nullable | Default | Storage |
Stats
target | Description
--------+---------+-----------+----------+---------+---------+--------------+-------------a      | integer |
|         |         | plain   |              |
 
Partition of: p FOR VALUES IN (1)
Partition constraint: ((a IS NOT NULL) AND (a = ANY (ARRAY[1])))

Thanks,
Amit

[1]

https://git.postgresql.org/gitweb/?p=postgresql.git;a=blobdiff;f=src/bin/psql/describe.c;h=d22ec68431e231d9c781c2256a6030d66e0fd09d;hp=6fb9bdd063583fb8b60ad282aeb5256df67942e4;hb=6f6b99d1335be8ea1b74581fc489a97b109dd08a;hpb=2cf15ec8b1cb29bea149559700566a21a790b6d3



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Re: [HACKERS] Partitions: \d vs \d+

From

Amit Langote

Date:

29 September 2017, 04:33:11

On 2017/09/28 22:19, Maksim Milyutin wrote:
> I also noticed ambiguity in printing "No partition constraint" in
> non-verbose mode and "Partition constraint:..." in verbose one for
> partition tables regardless of the type of partition.
> Attached small patch removes any output about partition constraint in
> non-verbose mode.

Patch looks good.

So, we should be looking at partconstraintdef only when verbose is true,
because that's only when we set it to a valid value.  Now, if
partconstraintdef is NULL even after verbose is true, that means backend
returned that there exists no constraint for that partition, which I
thought would be true for a default partition (because the commit that
introduced default partitions also introduced "No partition constraint"),
but it's really not.

For example, \d and \d+ show contradictory outputs for a default partition.

create table p (a int) partition by list (a);
create table p1 partition of p for values in (1);
create table pd partition of p default;

\d pd                Table "public.pd"Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------a      | integer |           |          |
Partition of: p DEFAULT
No partition constraint

\d+ pd                                   Table "public.pd"Column |  Type   | Collation | Nullable | Default | Storage |
Stats
target | Description
--------+---------+-----------+----------+---------+---------+--------------+-------------a      | integer |
|         |         | plain   |              |

Partition of: p DEFAULT
Partition constraint: (NOT ((a IS NOT NULL) AND (a = ANY (ARRAY[1]))))

Perhaps, there is no case when "No partition constraint" should be output,
but I may be missing something.

Thanks,
Amit

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Re: [HACKERS] Partitions: \d vs \d+

From

Maksim Milyutin

Date:

29 September 2017, 12:18:28

On 29.09.2017 04:33, Amit Langote wrote:

So, we should be looking at partconstraintdef only when verbose is true,
because that's only when we set it to a valid value.  Now, if
partconstraintdef is NULL even after verbose is true, that means backend
returned that there exists no constraint for that partition, which I
thought would be true for a default partition (because the commit that
introduced default partitions also introduced "No partition constraint"),
but it's really not.

For example, \d and \d+ show contradictory outputs for a default partition.

create table p (a int) partition by list (a);
create table p1 partition of p for values in (1);
create table pd partition of p default;

\d pd                Table "public.pd"Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------a      | integer |           |          |
Partition of: p DEFAULT
No partition constraint

\d+ pd                                   Table "public.pd"Column |  Type   | Collation | Nullable | Default | Storage | Stats
target | Description
--------+---------+-----------+----------+---------+---------+--------------+-------------a      | integer |           |          |         | plain   |              |
Partition of: p DEFAULT
Partition constraint: (NOT ((a IS NOT NULL) AND (a = ANY (ARRAY[1]))))


Perhaps, there is no case when "No partition constraint" should be output,
but I may be missing something.

Anyhow, we have to protect ourselves from empty output from pg_get_partition_constraintdef. And printing No partition constraint would be good point to start to examine why we didn't get any constraint definition.

-- 
Regards,
Maksim Milyutin

Re: [HACKERS] Partitions: \d vs \d+

From

Robert Haas

Date:

29 September 2017, 23:03:41

On Thu, Sep 28, 2017 at 9:33 PM, Amit Langote
<Langote_Amit_f8@lab.ntt.co.jp> wrote:
> Perhaps, there is no case when "No partition constraint" should be output,
> but I may be missing something.

The case arises when a partitioned table has a default partition but
no other partitions.

I have committed the patch.

In v10, it's impossible to have a partition with no partition
constraint, and if it does happen due to some bug, the worst that will
happen is \d will just print nothing, rather than explicitly printing
that there's no constraint.  That's not a serious problem and it
shouldn't happen anyway, so no back-patch.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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