| From: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Subject: | Re: [PATCH 3/8] Add support for a generic wal reading facility dubbed XLogReader |
| Date: | 2012-09-17 10:52:32 |
| Message-ID: | 505700F0.20800@vmware.com |
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| Lists: | pgsql-hackers |
On 17.09.2012 12:07, Andres Freund wrote:
> On Monday, September 17, 2012 10:30:35 AM Heikki Linnakangas wrote:
>> The user of the facility doesn't need to be aware of record boundaries,
>> that's the responsibility of the facility. I thought that's exactly the
>> point of generalizing this thing, to make it unnecessary for the code
>> that uses it to be aware of such things.
> With the proposed API it seems pretty much a requirement to wait inside the
> callback.
Or you can return false from the XLogPageRead() callback if the
requested page is not available. That will cause ReadRecord() to return
NULL, and you can retry when more WAL is available.
- Heikki
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