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From "Paul Joseph Davis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-1670) Replicator crashes if numbers in checkpoint docs are expressed in scientific notation
Date Thu, 07 Feb 2013 04:53:15 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-1670?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13573190#comment-13573190
] 

Paul Joseph Davis commented on COUCHDB-1670:
--------------------------------------------

Jason and Jens are right here, although I do find it a bit surprising that we actually have
an issue here given how erlang treats numbers. My only guess is that we have a guard for is_integer/1
instead of is_number/1 which would badarg on the parsed value (mochijson2 at least would parse
that as a float).

Couple minor comments on discussion:

[~snej] has it right in that we can't expect that JSON will roundtrip byte-for-byte when we
have an intermediary translation into an Erlang representation. We already rely on them facts
so that we can tell people to sshh when we mutate number representations.

[~jhs] Is kinda right but its not just a series of numerals, though its not much more than
"looks like a valid number". While the encoding differences aren't quite white space difference
levels, they are definitely in below the threshold of what we should tolerate, especially
considering what we're using them for.

I also have no idea what [~jhs] is talking about with whitespace in the key. If there's truth
to that then it sounds like a bug and not just "merely" a json encoding difference.

[~jhs] is also quoting Postel's law which is a crock and I have spent much time trying to
quash the influence of that terrible idea in the project. The number of times I've gotten
pissed trying to remember if its descending=true or reverse=true and checking if I have typos
is annoyingly non-zero.

[~wohali] is also right in the generic sense that since (hehehe) should not be restricted
to a numerical value and if we didn't have what appear to be laten bugs based on that assumption
this probably wouldn't even be an issue.

And if y'all want to spend more time on this, start investigating round tripping the value
1.1 through a JSON decoder/encoder pair. I'll be here with the tissues when you get to asserting
56bit rounding precisions with the GNU libc strtod assumptions.
                
> Replicator crashes if numbers in checkpoint docs are expressed in scientific notation
> -------------------------------------------------------------------------------------
>
>                 Key: COUCHDB-1670
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1670
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Replication
>            Reporter: Jens Alfke
>
> The CouchDB 1.2 replicator process crashes with an Erlang exception when parsing a checkpoint
document read back from a remote database, if numbers in the document were JSON-encoded in
scientific notation instead of as integers. This includes the properties source_last_seq,
end_last_seq, start_last_seq.
> That is, the following encoding works fine:
>     ..., "source_last_seq": 1234567, ...
> whereas this completely-equivalent encoding causes an exception:
>     ..., "source_last_seq": 1.234567e+06, ...
> This issue raised its head as a result of a CouchDB-compatible engine I'm writing (the
Couchbase Sync Gateway) which can serve as a passive replication endpoint. It's implemented
in Go, and the Go JSON package has the side effect of (a) parsing all JSON numbers into type
'double', and (b) encoding all doubles into JSON using scientific notation if they're more
than six digits long. The net effect is that when CouchDB stores a checkpoint into the Sync
Adapter's database and then later reads it back, it barfs due to the scientific notation.

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