RE: Parallel copy

> > 4.
> > A suggestion for CacheLineInfo.
> >
> > It use appendBinaryStringXXX to store the line in memory.
> > appendBinaryStringXXX will double the str memory when there is no enough
> spaces.
> >
> > How about call enlargeStringInfo in advance, if we already know the whole
> line size?
> > It can avoid some memory waste and may impove a little performance.
> >
>
> Here we will not know the size beforehand, in some cases we will start
> processing the data when current block is populated and keep processing
> block by block, we will come to know of the size at the end. We cannot use
> enlargeStringInfo because of this.
>
> Attached v11 patch has the fix for this, it also includes the changes to
> rebase on top of head.

Thanks for the explanation.

I think there is still chances we can know the size.

+ * line_size will be set. Read the line_size again to be sure if it is
+ * completed or partial block.
+ */
+ dataSize = pg_atomic_read_u32(&lineInfo->line_size);
+ if (dataSize != -1)
+ {

If I am not wrong, this seems the branch that procsssing the populated block.
I think we can check the copiedSize here, if copiedSize == 0, that means
Datasizes is the size of the whole line and in this case we can do the enlarge.

Best regards,
houzj