SQLITE_DBCONFIG_MAINDBNAME
,
SQLITE_DBCONFIG_LOOKASIDE
,
SQLITE_DBCONFIG_ENABLE_FKEY
,
SQLITE_DBCONFIG_ENABLE_TRIGGER
,
SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER
,
SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION
,
SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE
,
SQLITE_DBCONFIG_ENABLE_QPSG
,
SQLITE_DBCONFIG_TRIGGER_EQP
,
SQLITE_DBCONFIG_RESET_DATABASE
,
SQLITE_DBCONFIG_DEFENSIVE
,
SQLITE_DBCONFIG_MAX
—
Database Connection Configuration Options
#define SQLITE_DBCONFIG_MAINDBNAME
#define SQLITE_DBCONFIG_LOOKASIDE
#define SQLITE_DBCONFIG_ENABLE_FKEY
#define SQLITE_DBCONFIG_ENABLE_TRIGGER
#define SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER
#define SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION
#define SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE
#define SQLITE_DBCONFIG_ENABLE_QPSG
#define SQLITE_DBCONFIG_TRIGGER_EQP
#define SQLITE_DBCONFIG_RESET_DATABASE
#define SQLITE_DBCONFIG_DEFENSIVE
#define SQLITE_DBCONFIG_MAX
These constants are the available integer configuration options that can be
passed as the second argument to the sqlite3_db_config() interface.
New configuration options may be added in future releases of
SQLite. Existing configuration options might be discontinued. Applications
should check the return code from sqlite3_db_config() to make sure that the
call worked. The sqlite3_db_config() interface will return a non-zero error
code if a discontinued or unsupported configuration option is invoked.
- SQLITE_DBCONFIG_LOOKASIDE
- This option takes three additional arguments that determine the lookaside
memory allocator configuration for the database connection. The first
argument (the third parameter to sqlite3_db_config() is a pointer to a
memory buffer to use for lookaside memory. The first argument after the
SQLITE_DBCONFIG_LOOKASIDE verb may be NULL in which case SQLite will
allocate the lookaside buffer itself using sqlite3_malloc(). The second
argument is the size of each lookaside buffer slot. The third argument is
the number of slots. The size of the buffer in the first argument must be
greater than or equal to the product of the second and third arguments.
The buffer must be aligned to an 8-byte boundary. If the second argument
to SQLITE_DBCONFIG_LOOKASIDE is not a multiple of 8, it is internally
rounded down to the next smaller multiple of 8. The lookaside memory
configuration for a database connection can only be changed when that
connection is not currently using lookaside memory, or in other words when
the "current value" returned by
sqlite3_db_status(D,SQLITE_CONFIG_LOOKASIDE,...) is zero. Any attempt to
change the lookaside memory configuration when lookaside memory is in use
leaves the configuration unchanged and returns SQLITE_BUSY.
- SQLITE_DBCONFIG_ENABLE_FKEY
- This option is used to enable or disable the enforcement of foreign key
constraints. There should be two additional arguments. The first argument
is an integer which is 0 to disable FK enforcement, positive to enable FK
enforcement or negative to leave FK enforcement unchanged. The second
parameter is a pointer to an integer into which is written 0 or 1 to
indicate whether FK enforcement is off or on following this call. The
second parameter may be a NULL pointer, in which case the FK enforcement
setting is not reported back.
- SQLITE_DBCONFIG_ENABLE_TRIGGER
- This option is used to enable or disable triggers. There should be two
additional arguments. The first argument is an integer which is 0 to
disable triggers, positive to enable triggers or negative to leave the
setting unchanged. The second parameter is a pointer to an integer into
which is written 0 or 1 to indicate whether triggers are disabled or
enabled following this call. The second parameter may be a NULL pointer,
in which case the trigger setting is not reported back.
- SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER
- This option is used to enable or disable the two-argument version of the
fts3_tokenizer() function which is part of the FTS3 full-text search
engine extension. There should be two additional arguments. The first
argument is an integer which is 0 to disable fts3_tokenizer() or positive
to enable fts3_tokenizer() or negative to leave the setting unchanged. The
second parameter is a pointer to an integer into which is written 0 or 1
to indicate whether fts3_tokenizer is disabled or enabled following this
call. The second parameter may be a NULL pointer, in which case the new
setting is not reported back.
- SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION
- This option is used to enable or disable the sqlite3_load_extension()
interface independently of the load_extension() SQL function. The
sqlite3_enable_load_extension() API enables or disables both the C-API
sqlite3_load_extension() and the SQL function load_extension(). There
should be two additional arguments. When the first argument to this
interface is 1, then only the C-API is enabled and the SQL function
remains disabled. If the first argument to this interface is 0, then both
the C-API and the SQL function are disabled. If the first argument is -1,
then no changes are made to state of either the C-API or the SQL function.
The second parameter is a pointer to an integer into which is written 0 or
1 to indicate whether sqlite3_load_extension() interface is disabled or
enabled following this call. The second parameter may be a NULL pointer,
in which case the new setting is not reported back.
- SQLITE_DBCONFIG_MAINDBNAME
- This option is used to change the name of the "main" database
schema. The sole argument is a pointer to a constant UTF8 string which
will become the new schema name in place of "main". SQLite does
not make a copy of the new main schema name string, so the application
must ensure that the argument passed into this DBCONFIG option is
unchanged until after the database connection closes.
- SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE
- Usually, when a database in wal mode is closed or detached from a database
handle, SQLite checks if this will mean that there are now no connections
at all to the database. If so, it performs a checkpoint operation before
closing the connection. This option may be used to override this
behaviour. The first parameter passed to this operation is an integer -
positive to disable checkpoints-on-close, or zero (the default) to enable
them, and negative to leave the setting unchanged. The second parameter is
a pointer to an integer into which is written 0 or 1 to indicate whether
checkpoints-on-close have been disabled - 0 if they are not disabled, 1 if
they are.
- SQLITE_DBCONFIG_ENABLE_QPSG
- The SQLITE_DBCONFIG_ENABLE_QPSG option activates or deactivates the query
planner stability guarantee (QPSG). When the QPSG is active, a single SQL
query statement will always use the same algorithm regardless of values of
bound parameters. The QPSG disables some query optimizations that look at
the values of bound parameters, which can make some queries slower. But
the QPSG has the advantage of more predictable behavior. With the QPSG
active, SQLite will always use the same query plan in the field as was
used during testing in the lab. The first argument to this setting is an
integer which is 0 to disable the QPSG, positive to enable QPSG, or
negative to leave the setting unchanged. The second parameter is a pointer
to an integer into which is written 0 or 1 to indicate whether the QPSG is
disabled or enabled following this call.
- SQLITE_DBCONFIG_TRIGGER_EQP
- By default, the output of EXPLAIN QUERY PLAN commands does not include
output for any operations performed by trigger programs. This option is
used to set or clear (the default) a flag that governs this behavior. The
first parameter passed to this operation is an integer - positive to
enable output for trigger programs, or zero to disable it, or negative to
leave the setting unchanged. The second parameter is a pointer to an
integer into which is written 0 or 1 to indicate whether
output-for-triggers has been disabled - 0 if it is not disabled, 1 if it
is.
- SQLITE_DBCONFIG_RESET_DATABASE
- Set the SQLITE_DBCONFIG_RESET_DATABASE flag and then run VACUUM in order
to reset a database back to an empty database with no schema and no
content. The following process works even for a badly corrupted database
file:
- If the database connection is newly opened, make sure it has read the
database schema by preparing then discarding some query against the
database, or calling sqlite3_table_column_metadata(), ignoring any
errors. This step is only necessary if the application desires to keep
the database in WAL mode after the reset if it was in WAL mode before
the reset.
- sqlite3_db_config(db, SQLITE_DBCONFIG_RESET_DATABASE, 1, 0);
- sqlite3_exec(db, "VACUUM", 0, 0, 0);
- sqlite3_db_config(db, SQLITE_DBCONFIG_RESET_DATABASE, 0, 0);
Because resetting a database is destructive and irreversible,
the process requires the use of this obscure API and multiple steps to
help ensure that it does not happen by accident.
- SQLITE_DBCONFIG_DEFENSIVE
- The SQLITE_DBCONFIG_DEFENSIVE option activates or deactivates the
"defensive" flag for a database connection. When the defensive
flag is enabled, language features that allow ordinary SQL to deliberately
corrupt the database file are disabled. The disabled features include but
are not limited to the following:
- The PRAGMA writable_schema=ON statement.
- Writes to the sqlite_dbpage virtual table.
- Direct writes to shadow tables.