Re: Binary support for pgoutput plugin

Hi Dave,

On 29/02/2020 18:44, Dave Cramer wrote:
>
>
> rebased and removed the catversion bump.

Looked into this and it generally seems okay, but I do have one gripe here:

> +                                     tuple->values[i].data = palloc(len + 1);
> +                                     /* and data */
> +
> +                                     pq_copymsgbytes(in, tuple->values[i].data, len);
> +                                     tuple->values[i].len = len;
> +                                     tuple->values[i].cursor = 0;
> +                                     tuple->values[i].maxlen = len;
> +                                     /* not strictly necessary but the docs say it is required */
> +                                     tuple->values[i].data[len] = '\0';
> +                                     break;
> +                             }
> +                     case 't':                       /* text formatted value */
> +                             {
> +                                     tuple->changed[i] = true;
> +                                     int len = pq_getmsgint(in, 4);  /* read length */
> 
>                                       /* and data */
> -                                     tuple->values[i] = palloc(len + 1);
> -                                     pq_copymsgbytes(in, tuple->values[i], len);
> -                                     tuple->values[i][len] = '\0';
> +                                     tuple->values[i].data = palloc(len + 1);
> +                                     pq_copymsgbytes(in, tuple->values[i].data, len);
> +                                     tuple->values[i].data[len] = '\0';
> +                                     tuple->values[i].len = len;

The cursor should be set to 0 in the text formatted case too if this is
how we chose to encode data.

However I am not quite convinced I like the StringInfoData usage here.
Why not just change the struct to include additional array of lengths
rather than replacing the existing values array with StringInfoData
array, that seems generally both simpler and should have smaller memory
footprint too, no?

We could also merge the binary and changed arrays into single char array
named something like format (as data can be either unchanged, binary or
text) and just reuse same identifiers we have in protocol.

--
Petr Jelinek
2ndQuadrant - PostgreSQL Solutions for the Enterprise
https://www.2ndQuadrant.com/