Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

I wrote:
> While I'm at it, I would like to strenuously object to the current
> framing of CreateAndCopyRelationData as a general-purpose copying
> mechanism.

And while I'm piling on, how is this bit in RelationCopyStorageUsingBuffer
not completely broken?

        /* Read block from source relation. */
        srcBuf = ReadBufferWithoutRelcache(src->rd_locator, forkNum, blkno,
                                           RBM_NORMAL, bstrategy_src,
                                           permanent);
        srcPage = BufferGetPage(srcBuf);
        if (PageIsNew(srcPage) || PageIsEmpty(srcPage))
        {
            ReleaseBuffer(srcBuf);
            continue;
        }

        /* Use P_NEW to extend the destination relation. */
        dstBuf = ReadBufferWithoutRelcache(dst->rd_locator, forkNum, P_NEW,
                                           RBM_NORMAL, bstrategy_dst,
                                           permanent);

You can't skip pages just because they are empty.  Well, maybe you could
if you were doing something to ensure that you zero-fill the corresponding
blocks on the destination side.  But this isn't doing that.  It's using
P_NEW for dstBuf, which will have the effect of silently collapsing out
such pages.  Maybe in isolation a heap could withstand that, but its
indexes won't be happy (and I guess t_ctid chain links won't either).

I think you should just lose the if() stanza.  There's no optimization to
be had here that's worth any extra complication.

(This seems worth fixing before beta3, as it looks like a rather
nasty data corruption hazard.)

            regards, tom lane