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## SQLite C Interface

## Virtual Table Configuration Options

>     #define SQLITE_VTAB_CONSTRAINT_SUPPORT 1
>     #define SQLITE_VTAB_INNOCUOUS          2
>     #define SQLITE_VTAB_DIRECTONLY         3
>     #define SQLITE_VTAB_USES_ALL_SCHEMAS   4

These macros define the various options to the sqlite3_vtab_config() interface that virtual table implementations can use to customize and optimize their behavior.

SQLITE_VTAB_CONSTRAINT_SUPPORT
  Calls of the form sqlite3_vtab_config(db,SQLITE_VTAB_CONSTRAINT_SUPPORT,X) are supported, where X is an integer. If X is zero, then the virtual table whose xCreate or xConnect method invoked sqlite3_vtab_config() does not support constraints. In this configuration (which is the default) if a call to the xUpdate method returns SQLITE_CONSTRAINT, then the entire statement is rolled back as if OR ABORT had been specified as part of the user's SQL statement, regardless of the actual ON CONFLICT mode specified.

  If X is non-zero, then the virtual table implementation guarantees that if xUpdate returns SQLITE_CONSTRAINT, it will do so before any modifications to internal or persistent data structures have been made. If the ON CONFLICT mode is ABORT, FAIL, IGNORE or ROLLBACK, SQLite is able to roll back a statement or database transaction, and abandon or continue processing the current SQL statement as appropriate. If the ON CONFLICT mode is REPLACE and the xUpdate method returns SQLITE_CONSTRAINT, SQLite handles this as if the ON CONFLICT mode had been ABORT.

  Virtual table implementations that are required to handle OR REPLACE must do so within the xUpdate method. If a call to the sqlite3_vtab_on_conflict() function indicates that the current ON CONFLICT policy is REPLACE, the virtual table implementation should silently replace the appropriate rows within the xUpdate callback and return SQLITE_OK. Or, if this is not possible, it may return SQLITE_CONSTRAINT, in which case SQLite falls back to OR ABORT constraint handling.

SQLITE_VTAB_DIRECTONLY
  Calls of the form sqlite3_vtab_config(db,SQLITE_VTAB_DIRECTONLY) from within the the xConnect or xCreate methods of a virtual table implementation prohibits that virtual table from being used from within triggers and views.

SQLITE_VTAB_INNOCUOUS
  Calls of the form sqlite3_vtab_config(db,SQLITE_VTAB_INNOCUOUS) from within the xConnect or xCreate methods of a virtual table implementation identify that virtual table as being safe to use from within triggers and views. Conceptually, the SQLITE_VTAB_INNOCUOUS tag means that the virtual table can do no serious harm even if it is controlled by a malicious hacker. Developers should avoid setting the SQLITE_VTAB_INNOCUOUS flag unless absolutely necessary.

SQLITE_VTAB_USES_ALL_SCHEMAS
  Calls of the form sqlite3_vtab_config(db,SQLITE_VTAB_USES_ALL_SCHEMA) from within the the xConnect or xCreate methods of a virtual table implementation instruct the query planner to begin at least a read transaction on all schemas ("main", "temp", and any ATTACH-ed databases) whenever the virtual table is used.

See also lists of Objects, Constants, and Functions.