Projects/PIM/MS Windows/SQLite Folder Indices

There are issues with locking index files for KMail folders and mmap()/munmap() operations on Windows. Therefore, SQLite-based indices are in development. This page presents detailed development notes for this task.

Started: jstaniek 11:35, 23 April 2008 (CEST)

Introduction

• we call the new implementation SQLite mode for short
• SQLite 3.5.4 is used, as provided by emerge sqlite module; we should not allow using much older versions of sqlite, e.g. 3.1 because of file format differences
• we are using one .index.db file per account, not folder
• kmfolderindex_sqlite.cpp is created and edited as a copy of kmfolderindex.cpp; kmfolderindex.cpp is not compiled in SQLite mode
• kmfolderindex.h is a common header for both kmfolderindex*.cpp implementations
• kmailprivate links to sqlite library, and KMAIL_SQLITE_INDEX is defined to enable #ifdef'd code

KMFolderIndex

api docs

• 2008-04-23
  • mIndexId unused - removed as well as serialIndexId()
  • indexLocation(): added .db suffix to indicate the index is sqlite-based
  • INDEX_VERSION is written and checked using 'PRAGMA user_version = <integer>' command [1]
  • we do not use temporary filenames, e.g. in writeIndex(): SQLite takes care about safe storage
  • updateIndex() no changes, we're changing implementation of KMMsgBase::syncIndexString() and writeIndex() instead

KMMsgBase

api docs

• 2008-04-23
  • move syncIndexString() to KMFolderIndex, where we can impleemnt it for SQLite differently

Status of porting to SQLite

TOPIC	PORTED	TESTED	NOTES
QString KMFolderIndex::indexLocation()	yes		added .db suffix to indicate the index is sqlite-based
int KMFolderIndex::updateIndex()	yes		no changes
int KMFolderIndex::writeIndex( bool createEmptyIndex )
bool KMFolderIndex::readIndex()
int KMFolderIndex::count(bool cache)	yes		no changes
bool KMFolderIndex::readIndexHeader(int *gv)
bool KMFolderIndex::updateIndexStreamPtr(bool)
KMFolderIndex::IndexStatus KMFolderIndex::indexStatus()
void KMFolderIndex::truncateIndex()			use "DELETE FROM..."
off_t KMFolderIndex::mHeaderOffset			replace its public use (e.g. in KMFolderIndex::truncateIndex()) with additional bool indexOpened()
KMFolderIndex::
KMFolderIndex::

Open Questions

• should we port .sorted files to sqlite too? (possibly to the same .db file)