Mailing List Message #206
From: OCsite <>
Subject: Re: ... too many snapshots?
Date: Thu, 17 Jun 2021 14:43:18 +0200
To: WebObjects & WOnder Development <>

On 17 Jun 2021, at 0:41, Ramsey Gurley <> wrote:
In particular, check out Mark Ritchie's Freshness Explorer application which lets you see how the different layers of the stack propagate changes.

Thanks, but it does not really help. Especially as of

I admit I am sort of lost in the things.

So far I lived in impression that (if we ignore undo) there's only one kind of snapshots: OSC-level shared snapshots of what-was-just-saved-into-DB.

I've tried to research the thing a bit and there seem to be at the very least the following snapshots:

(i) EC.committedSnapshotForObject
(ii) EC.currentEventSnapshotForObject
(iii) EODatabaseContext.snapshotForGlobalID
(iv) EODatabaseContext.localSnapshotForGlobalID

I regret to say the standard documentation does not help much. I did some testing and it looks like

- (iii) is the one snapshot I knew: whenever save finishes, it always contains the newly saved values
- (i) and (ii) — which for me always contain same data, that's weird! — seem to contain an EC-level snapshot stored at its (first) willChange. Also it looks like those “locally uncommitted changes” are based on (one of) these. So far though I haven't found a case when (i) would differ from (ii)... although, based on the name, I would actually presume (i) should be the same as (iii). It very definitely is not.
- (iv) I don't understand at all :(

Are those things somewhere documented in detail?

it never touches those suspicious EC.xxxSnapshotForObject things; and the particular code it uses, namely,

EODatabaseContext databaseContext = (EODatabaseContext) osc.objectStoreForGlobalID(gid);
EODatabase database = databaseContext.database();
snapshot = database.snapshotForGlobalID(gid);

just brings a suspicion whether this things differs from (iii)/(iv) above, and if so, how :(

If anybody knows of a good documentation of all those snapshots, how they differ, when they are created and how they are used, I'd be really grateful.

Thanks and all the best,

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