Code review comment for lp:~jameinel/bzr/1.16-commit-fulltext

John A Meinel (jameinel) wrote :

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Robert Collins wrote:
> On Tue, 2009-06-02 at 20:50 +0000, John A Meinel wrote:
>> John A Meinel has proposed merging lp:~jameinel/bzr/1.16-commit-fulltext into lp:bzr.
>>
>> Requested reviews:
>> bzr-core (bzr-core)
>>
>> This branch adds a new api, VersionedFiles.add_text(). If people really want, I could change it to VF.add_chunks(), but add_text() fits what I needed, and was expedient.
>
> Is it at all possible to use insert_record_stream?
>
> I'd really like to shrink the VF surface area, not increase it.
>
> -Rob
>

Not trivially.

1) It is an incompatible api change to insert_record_stream

2) It requires setting up a FulltextContextFactory and passing in a
stream of 1 entry just to add a text, which isn't particularly nice.

3) It requires adding lots of parameters like 'nostore_sha', and
'random_id', etc, onto insert_record_stream

4) It requires rewriting the internals of
KnitVersionedFiles.insert_record_stream to *not* thunk back to
self.add_lines(chunks_to_lines(record.get_bytes_as('chunked')))

5) nostore_sha especially doesn't fit with the theology of
insert_record_stream. It is really only applicable to a single text, and
insert_record_stream is really designed around many texts. Wedging new
parameters onto a function where it doesn't really fit doesn't seem
*better*.

6) As for VF surface area, there is at least a default implementation
that simply thunks over to .add_lines() for those that don't strictly
care about memory performance. (And thus works fine for Weaves, etc.)

In theory we could try to layer it so that we had an 'ongoing' stream,
and 'yield' texts to be inserted as we find them. But that really
doesn't fit 'nostore_sha' since that also needs to be passed in, and
needs to raise an exception which breaks the stream.
Also, I thought we *wanted* commit for groupcompress to not have to do
deltas, and if we stream the texts in, we would spend a modest amount of
time getting poor compression between text files. (Note that we were
already spending that time to compute the delta index, but I have a
patch which fixes that.)

I can understand wanting to shrink the api. If you really push on it,
I'm willing to deprecate .add_lines() and write a .add_chunks() that is
meant to replace it. (since you can .add_chunks(lines) and
.add_chunks([text])) However, chunks fits slightly worse for knits,
since the Content code and annotation and deltas needs lines anyway, and
Groupcompress wants fulltexts...

So if you push hard, I'll try to find the time to do it. But this was
*much* easier.

John
=:->

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