Add comments to explain the role of the ota vfs.

FossilOrigin-Name: 7bb633639d1e41067903a49653f09a823054e213

diff --git a/ext/ota/sqlite3ota.c b/ext/ota/sqlite3ota.c
index 2e23d5658cfa4f81becefe897d32cc5dfe8ba0cd..cf408b8b9f49facfebd9ceaf2b045791a20d662e 100644 (file)
--- a/ext/ota/sqlite3ota.c
+++ b/ext/ota/sqlite3ota.c
@@ -2153,15 +2153,36 @@ sqlite3_int64 sqlite3ota_progress(sqlite3ota *pOta){
 ** Beginning of OTA VFS shim methods. The VFS shim modifies the behaviour
 ** of a standard VFS in the following ways:
 **
-**   TODO
+**   1. Whenever the first page of an OTA target database file is read or 
+**      written, the value of the change-counter cookie is stored in
+**      sqlite3ota.iCookie. This ensures that, so long as a read transaction
+**      is held on the db file, the value of sqlite3ota.iCookie matches
+**      that stored on disk.
+**
+**   2. When the ota handle is in OTA_STAGE_OAL or OTA_STAGE_CKPT state, all
+**      EXCLUSIVE lock attempts on the target database fail. This prevents
+**      sqlite3_close() from running an automatic checkpoint. Until the
+**      ota handle reaches OTA_STAGE_DONE - at that point the automatic
+**      checkpoint may be required to delete the *-wal file.
+**
+**   3. In OTA_STAGE_OAL, the *-shm file is stored in memory. All xShmLock()
+**      calls are noops.
+**
+**   4. In OTA_STAGE_OAL mode, when SQLite calls xAccess() to check if a
+**      *-wal file associated with the target database exists, the following
+**      special handling applies:
+**
+**        a) if the *-wal file does exist, return SQLITE_CANTOPEN. An OTA
+**           target database may not be in wal mode already.
+**
+**        b) if the *-wal file does not exist, set the output parameter to
+**           non-zero (to tell SQLite that it does exist) anyway.
+**
+**   5. In OTA_STAGE_OAL mode, if SQLite tries to open a *-wal file 
+**      associated with a target database, open the corresponding *-oal file
+**      instead.
 */
 
-#if 0
-#define OTA_FILE_VANILLA    0
-#define OTA_FILE_TARGET_DB  1
-#define OTA_FILE_TARGET_WAL 2
-#endif
-
 typedef struct ota_file ota_file;
 typedef struct ota_vfs ota_vfs;
 

diff --git a/manifest b/manifest
index 93b2368df6ed69bae88c6f88aa03d7ee2237a4b0..777601fb6b3546cf3bb55ea383caedce668cad0a 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Remove\s"PRAGMA\spager_ota_mode".
-D 2015-02-07T19:17:36.157
+C Add\scomments\sto\sexplain\sthe\srole\sof\sthe\sota\svfs.
+D 2015-02-07T20:20:32.171
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 6b9e7677829aa94b9f30949656e27312aefb9a46
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -134,7 +134,7 @@ F ext/ota/ota7.test 1fe2c5761705374530e29f70c39693076028221a
 F ext/ota/ota8.test cd70e63a0c29c45c0906692827deafa34638feda
 F ext/ota/ota9.test d3eee95dd836824d07a22e5efcdb7bf6e869358b
 F ext/ota/otafault.test 508ba87c83d632670ac0f94371a465d4bb4d49dd
-F ext/ota/sqlite3ota.c 7015400382d1d6655626046f2c1763634dd8a168
+F ext/ota/sqlite3ota.c a5cea44e3d186ae53c1a0dbdc1c3ca73e9d1dc62
 F ext/ota/sqlite3ota.h b4c54c7df5d223f2ee40efa5ba363188daa3ad37
 F ext/rtree/README 6315c0d73ebf0ec40dedb5aa0e942bc8b54e3761
 F ext/rtree/rtree.c 14e6239434d4e3f65d3e90320713f26aa24e167f
@@ -1253,10 +1253,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P c3931db560ab4a2601c7f7318fb02c8d5e6862b1
-R 8cb076bc2c2cc0b3b28786011832c69d
-T *branch * ota-update-no-pager_ota_mode
-T *sym-ota-update-no-pager_ota_mode *
-T -sym-ota-update *
+P 8ac58e46782bd6b81c06fdf1cb5b316b8a4e1ddf
+R f5474ed197582e342ea21c91b796b802
 U dan
-Z b552e61eecb5b9b2a0bf7b3905abae17
+Z 4e62cdaf7cd09d75059d0dc1ee3d7cb0

diff --git a/manifest.uuid b/manifest.uuid
index 78b4daf1f53e1f42ddfc01a4fb0bd9524742fba9..489302fa8ed836c333a791f7e58e99e7085f9e3d 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-8ac58e46782bd6b81c06fdf1cb5b316b8a4e1ddf
\ No newline at end of file
+7bb633639d1e41067903a49653f09a823054e213
\ No newline at end of file