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SQLite Requirement Matrix Details
wal.html
Index Summary Markup Original
R-58297-14483-40146-32998-13341-07144-06303-13895 tcl slt th3 src
WAL databases can be created, read, and written even if shared memory is unavailable as long as the locking_mode is set to EXCLUSIVE before the first attempted access.
tcl/e_wal.test:22 th3/req1/pragma05.test:188
/* IMP: R-58297-14483 */
# EVIDENCE-OF: R-58297-14483 WAL databases can be created, read, and # written even if shared memory is unavailable as long as the # locking_mode is set to EXCLUSIVE before the first attempted access.
R-00449-33772-33919-59402-60829-28733-22208-04727 tcl slt th3 src
This feature allows WAL databases to be created, read, and written by legacy VFSes that lack the "version 2" shared-memory methods xShmMap, xShmLock, xShmBarrier, and xShmUnmap on the sqlite3_io_methods object.
tcl/e_wal.test:26 th3/req1/pragma05.test:192
/* IMP: R-00449-33772 */
# EVIDENCE-OF: R-00449-33772 This feature allows WAL databases to be # created, read, and written by legacy VFSes that lack the "version 2" # shared-memory methods xShmMap, xShmLock, xShmBarrier, and xShmUnmap on # the sqlite3_io_methods object.
R-31969-57825-42101-14521-32158-26846-01551-49036 tcl slt th3 src
If EXCLUSIVE locking mode is set prior to the first WAL-mode database access, then SQLite never attempts to call any of the shared-memory methods and hence no shared-memory wal-index is ever created.
tcl/e_wal.test:81 th3/req1/pragma05.test:217
/* IMP: R-31969-57825 */
# EVIDENCE-OF: R-31969-57825 If EXCLUSIVE locking mode is set prior to # the first WAL-mode database access, then SQLite never attempts to call # any of the shared-memory methods and hence no shared-memory wal-index # is ever created.
R-36328-16367-14145-21377-30808-40796-28392-26990 tcl slt th3 src
In that case, the database connection remains in EXCLUSIVE mode as long as the journal mode is WAL; attempts to change the locking mode using "PRAGMA locking_mode=NORMAL;" are no-ops.
tcl/e_wal.test:96 th3/req1/pragma05.test:237
/* IMP: R-36328-16367 */
# EVIDENCE-OF: R-36328-16367 In that case, the database connection # remains in EXCLUSIVE mode as long as the journal mode is WAL; attempts # to change the locking mode using "PRAGMA locking_mode=NORMAL;" are # no-ops.
R-63522-46088-33895-54497-03733-53184-07098-33228 tcl slt th3 src
The only way to change out of EXCLUSIVE locking mode is to first change out of WAL journal mode.
tcl/e_wal.test:111 th3/req1/pragma05.test:247
/* IMP: R-63522-46088 */
# EVIDENCE-OF: R-63522-46088 The only way to change out of EXCLUSIVE # locking mode is to first change out of WAL journal mode.
R-57239-11845-16463-18106-13303-34365-12787-00637 tcl slt th3 src
If NORMAL locking mode is in effect for the first WAL-mode database access, then the shared-memory wal-index is created.
tcl/e_wal.test:134 th3/req1/pragma05.test:256
/* IMP: R-57239-11845 */
# EVIDENCE-OF: R-57239-11845 If NORMAL locking mode is in effect for the # first WAL-mode database access, then the shared-memory wal-index is # created.
R-46197-42811-45122-27334-03540-14095-05781-43695 tcl slt th3 src
This means that the underlying VFS must support the "version 2" shared-memory.
tcl/e_wal.test:183 th3/req1/pragma05.test:260
/* IMP: R-46197-42811 */
# EVIDENCE-OF: R-46197-42811 This means that the underlying VFS must # support the "version 2" shared-memory.
R-55316-21772-61172-01789-50748-54713-63157-59070 tcl slt th3 src
If the VFS does not support shared-memory methods, then the attempt to open a database that is already in WAL mode, or the attempt convert a database into WAL mode, will fail.
tcl/e_wal.test:186 th3/req1/pragma05.test:290
/* IMP: R-55316-21772 */
# EVIDENCE-OF: R-55316-21772 If the VFS does not support shared-memory # methods, then the attempt to open a database that is already in WAL # mode, or the attempt convert a database into WAL mode, will fail.
R-13779-07711-12405-44335-29719-17285-28240-52263 tcl slt th3 src
As long as exactly one connection is using a shared-memory wal-index, the locking mode can be changed freely between NORMAL and EXCLUSIVE.
tcl/e_wal.test:149 th3/req1/pragma05.test:277
/* IMP: R-13779-07711 */
# EVIDENCE-OF: R-13779-07711 As long as exactly one connection is using # a shared-memory wal-index, the locking mode can be changed freely # between NORMAL and EXCLUSIVE.
R-10993-11647-55800-55293-06436-13332-42842-10882 tcl slt th3 src
It is only when the shared-memory wal-index is omitted, when the locking mode is EXCLUSIVE prior to the first WAL-mode database access, that the locking mode is stuck in EXCLUSIVE.
tcl/e_wal.test:164 th3/req1/pragma05.test:312
/* IMP: R-10993-11647 */
# EVIDENCE-OF: R-10993-11647 It is only when the shared-memory wal-index # is omitted, when the locking mode is EXCLUSIVE prior to the first # WAL-mode database access, that the locking mode is stuck in EXCLUSIVE.
R-45540-25505-12705-13417-45651-45483-56013-24623 tcl slt th3 src
To prevent older versions of SQLite (prior to version 3.7.0, 2010-07-22) from trying to recover a WAL-mode database (and making matters worse) the database file format version numbers (bytes 18 and 19 in the database header) are increased from 1 to 2 in WAL mode.
/* IMP: R-45540-25505 */
# EVIDENCE-OF: R-45540-25505 To prevent older versions of SQLite (prior # to version 3.7.0, 2010-07-22) from trying to recover a WAL-mode # database (and making matters worse) the database file format version # numbers (bytes 18 and 19 in the database header) are increased from 1 # to 2 in WAL mode.
R-02535-05811-23269-15824-03293-63258-54375-28501 tcl slt th3 src
One can explicitly change out of WAL mode using a pragma such as this:
PRAGMA journal_mode=DELETE;
/* IMP: R-02535-05811 */
# EVIDENCE-OF: R-02535-05811 One can explicitly change out of WAL mode # using a pragma such as this: PRAGMA journal_mode=DELETE;
R-60175-02388-07986-54483-25650-07763-57471-09194 tcl slt th3 src
Deliberately changing out of WAL mode changes the database file format version numbers back to 1 so that older versions of SQLite can once again access the database file.
/* IMP: R-60175-02388 */
# EVIDENCE-OF: R-60175-02388 Deliberately changing out of WAL mode # changes the database file format version numbers back to 1 so that # older versions of SQLite can once again access the database file.