Re: block-level incremental backup

On Mon, Sep 9, 2019 at 4:51 PM Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com>
wrote:
>
>
>
> On Tue, Aug 27, 2019 at 4:46 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:
>>
>> Few comments:
>> Comment:
>> + buf = (char *) malloc(statbuf->st_size);
>> + if (buf == NULL)
>> + ereport(ERROR,
>> + (errcode(ERRCODE_OUT_OF_MEMORY),
>> + errmsg("out of memory")));
>> +
>> + if ((cnt = fread(buf, 1, statbuf->st_size, fp)) > 0)
>> + {
>> + Bitmapset *mod_blocks = NULL;
>> + int nmodblocks = 0;
>> +
>> + if (cnt % BLCKSZ != 0)
>> + {
>>
>> We can use same size as full page size.
>> After pg start backup full page write will be enabled.
>> We can use the same file size to maintain data consistency.
>
>
> Can you please explain which size?
> The aim here is to read entire file in-memory and thus used
statbuf->st_size.
>
Instead of reading the whole file here, we can read the file page by page.
There is a possibility of data inconsistency if data is not read page by
page, data will be consistent if read page by page as full page write will
be enabled at this time.

Regards,
Vignesh
EnterpriseDB: http://www.enterprisedb.com