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User:Rkent/Folder Data Persistence: Difference between revisions
User:Rkent/Folder Data Persistence (view source)
Revision as of 20:34, 1 November 2014
, 1 November 2014→Analysis: details on specific calls
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As a general rule, changes to folder metadata is first written to dbFolderInfo without doing changes on the equivalent member variables in the msgFolder. The variables in the msgFolder are changed at the end of operations, reading from dbFolderInfo in ReadDBFolderInfo. | As a general rule, changes to folder metadata is first written to dbFolderInfo without doing changes on the equivalent member variables in the msgFolder. The variables in the msgFolder are changed at the end of operations, reading from dbFolderInfo in ReadDBFolderInfo. | ||
=== ReadDBFolderInfo(force) === | |||
nsMsgDBFolder::ReadDBFolderInfo(bool force) when force==false is a no-op except for the first time a folder is created, where the folder member objects for folder metadata are initialized from the folder cache. | |||
ReadDBFolderInfo(false) is used typically in a Get...() call, where you want to make sure that the variable has been initialized from the cache before returning it. | |||
ReadDBFolderInfo(true) is used typically after folder metadata has changed in dbFolderInfo, and you want to update the folder member variables, typically also doing any required notifications. See nsMsgDBFolder::UpdateSummaryTotals | |||
=== UpdateSummaryTotals(force) === | |||
In all cases, UpdateSummaryTotals will: | |||
* Initialize member variables using ReadDBFolderInfo(force) | |||
* Notify changes in kTotalMessagesAtom and kTotalUnreadMessagesAtom | |||
* call FlushToFolderCache to update the cache. | |||
When force==true, then the objects are read from dbFolderInfo, so this is the method used to update relevant member variables by reading from dbFolderInfo, doing folder-level notifications, and flushing the changes to the folderCache. | |||
When force==false the situation is trickier. Member variables are initialized from the folder cache, with notifications, without opening the database. This is done when the folder object is first initialized (in GetSubfolders), or in SummaryChanged(). | |||
=== SummaryChanged() === | |||
This is just a synonym for UpdateSummaryTotals(false), and is only used in IMAP. Its main purpose seems to be to write folder metadata to the folder cache. This assumes that the metadata was written to dbFolderInfo at the time it was changed. One common use seems to be after ChangeNumPending... which does changes in dbFolderInfo and notifications but not in folderCache. The call to UpdateSummaryTotals(false) only flushes the changes to the folder cache. | |||