"Pinning" a table in memory
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Eric24
Jul 19, 2016, 3:53:52 PM7/19/16
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Is there any mechanism (in ODB 2.2.x) to "pin" a specific table in a database in memory?
Essentially, within a normal plocal disk-backed database, I want to select a specific table that is always guaranteed to be in memory (obviously my application is making sure that this table is maintained in such a way that it doesn't grow later than the available memory, while still allowing plenty of memory for general caching, etc.). I still want the "in memory" table to be persisted to disk, but want it to be "pinned" to ensure the highest level of performance on reads. (Note that I don't expect that the "first read" of a particular record after a server restart would already be in memory, although that would be nice future enhancement--active pre-loading from disk of a designated "pinned" table).
I could almost accomplish what I'm looking for by creating a small in-memory database with just this one table, but in addition to this table not being persisted to disk, it also makes it more difficult to interact with other tables in the "main" database when necessary.
And the other downside is that in-memory databases can't currently be replicated (planned for 3.0: http://orientdb.com/docs/last/Roadmap.html). Just out of curiosity, is this still on track?
--Eric
scott molinari
Jul 20, 2016, 3:22:36 AM7/20/16
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I'd also love to see a memory only class in ODB.
Scott
Jacksen K
Jul 20, 2016, 4:07:15 AM7/20/16
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A persisted in memory class would be great!
Andrey Lomakin
Jul 20, 2016, 4:09:25 AM7/20/16
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Hi Guys,
We have all underlying infrastructure ready for that.
If you wish such feature could you fill in a feature request (that is not hard to do).
But of course, it may mean that other queries including other tables and indexes will be slower.
On Wed, Jul 20, 2016 at 11:07 AM Jacksen K <jackse...@gmail.com> wrote:
A persisted in memory class would be great!
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Eric Lenington
Jul 20, 2016, 10:31:54 AM7/20/16
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OK. I'll do that later today. If anyone has any specific suggestions you'd like to see as part of this request, please reply to this thread in the mean time (and please label as "critical", "important", and "nice to have").
--Eric
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scott molinari
Jul 20, 2016, 10:41:33 AM7/20/16
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Hey Eric. Already done!
https://github.com/orientechnologies/orientdb/issues/6447
Hope you don't mind.
Scott
https://github.com/orientechnologies/orientdb/issues/6447
Hope you don't mind.
Scott
Luca Garulli
Jul 20, 2016, 12:24:49 PM7/20/16
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Funny thing: this feature was already existent with the old LOCAL storage :-)
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Eric Lenington
Jul 20, 2016, 6:43:51 PM7/20/16
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@scott: No problem--thanks!
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Andrey Lomakin
Jul 21, 2016, 4:34:39 AM7/21/16
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Luca,
Do you mean in memory clusters? That is different.
In memory clusters never stored data to disk.
But this feature is opposite, data stored to disk but cached on memory without a flush out to the disk.
Andrey Lomakin
Jul 21, 2016, 4:54:06 AM7/21/16
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Hi Luca,
Just read the issue, I was wrong, that is exactly the same.
Eric Lenington
Jul 21, 2016, 10:56:50 AM7/21/16
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@Luca: How does it help that it used to exist in LOCAL storage? What I'm looking for is a class in PLOCAL that works in every way the same as any other class (specifically including replication), but is guaranteed to be 100% in memory and has the option of being persisted to disk or not.
--Eric
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Luca Garulli
Jul 21, 2016, 12:31:35 PM7/21/16
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@Eric, doesn't help, it was funny that we had this feature with the old LOCAL storage engine.
Anyway, even if implementing this should be quite trivial, Andrey could have a better idea about how to do that.
Eric Lenington
Jul 21, 2016, 12:34:09 PM7/21/16
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@Luca, I was looking for some old docs on how this was configured with LOCAL, but I couldn't find anything. Do you have a link by any chance?
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