Re: Declarative partitioning - another take

On Wed, Dec 7, 2016 at 6:42 AM, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> On 2016/12/07 13:38, Robert Haas wrote:
>> On Wed, Nov 30, 2016 at 10:56 AM, Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
>>> The latest patch I posted earlier today has this implementation.
>>
>> I decided to try out these patches today with #define
>> CLOBBER_CACHE_ALWAYS 1 in pg_config_manual.h, which found a couple of
>> problems:
>>
>> 1. RelationClearRelation() wasn't preserving the rd_partkey, even
>> though there's plenty of code that relies on it not changing while we
>> hold a lock on the relation - in particular, transformPartitionBound.
>
> Oh, I thought an AccessExclusiveLock on the relation would prevent having
> to worry about that, but guess I'm wrong. Perhaps, having a lock on a
> table does not preclude RelationClearRelation() resetting the table's
> relcache.

No, it sure doesn't. The lock prevents the table from actually being
changed, so a reload will find data equivalent to what it had before,
but it doesn't prevent the backend's cache from being flushed.

>> 2. partition_bounds_equal() was using the comparator and collation for
>> partitioning column 0 to compare the datums for all partitioning
>> columns. It's amazing this passed the regression tests.
>
> Oops, it seems that the regression tests where the above code might be
> exercised consisted only of range partition key with columns all of the
> same type: create table test(a int, b int) partition by range (a, (a+b));

It doesn't seem like it; you had this: create table part1 partition of
range_parted for values from ('a', 1) to ('a', 10);

>> I recommend that once you fix this, you run 'make check' with #define
>> CLOBBER_CACHE_ALWAYS 1 and look for other hazards. Such mistakes are
>> easy to make with this kind of patch.
>
> With the attached latest version of the patches, I couldn't see any
> failures with a CLOBBER_CACHE_ALWAYS build.

Cool.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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