Re: README of hash index

On Fri, Sep 16, 2016 at 9:56 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
> On Fri, Sep 16, 2016 at 4:20 AM, Amit Kapila <amit.kapila16@gmail.com>
> wrote:
>>
>> Currently README of hash module contain algorithms written in below form.
>>
>> The insertion algorithm is rather similar:
>>
>> pin meta page and take buffer content lock in shared mode
>> loop:
>> compute bucket number for target hash key
>> release meta page buffer content lock
>> if (correct bucket page is already locked)
>> break
>> release any existing bucket page lock (if a concurrent split happened)
>> take heavyweight bucket lock in shared mode
>> retake meta page buffer content lock in shared mode
>> -- (so far same as reader)
>> release pin on metapage
>> ..
>> ..
>>
>> I have mostly updated them in the patches I have proposed to improve
>> hash index.  However, each time I try to update them, I find that it
>> is easy to follow the code than to read and understand the existing
>> algorithm written in above form from README.
>>
>> Do others find it useful to maintain the algorithms in above form?
>
>
> I think that having them all condensed into one place makes it easier to
> think through the locking models to decide if there might be races or
> deadlocks.  If you only care about the algorithm for inserting in isolation,
> I agree reading the code might be better.
>


Thanks Jeff and Ken for the inputs.  I will keep the algorithms
updated in README of hash index.


-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com