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SQLITE_DBCONFIG_MAINDBNAME(3) Library Functions Manual
NAME
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
SYNOPSIS
#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
DESCRIPTION
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:
1. 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.
2. sqlite3_db_config(db, SQLITE_DBCONFIG_RESET_DATABASE, 1, 0);
3. sqlite3_exec(db, "VACUUM", 0, 0, 0);
4. 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.
SEE ALSO
sqlite3(3), sqlite3_db_config(3), sqlite3_db_status(3),
sqlite3_enable_load_extension(3), sqlite3_exec(3),
sqlite3_load_extension(3), sqlite3_malloc(3), SQLITE_OK(3),
SQLITE_CONFIG_SINGLETHREAD(3)
NetBSD 9.99 December 19, 2018 NetBSD 9.99