NAME
sqlite3_stmt_readonly —
Determine If An
SQL Statement Writes The Database
SYNOPSIS
int
sqlite3_stmt_readonly(
sqlite3_stmt
*pStmt);
DESCRIPTION
The sqlite3_stmt_readonly(X) interface returns true (non-zero) if and only if
the prepared statement X makes no direct changes to the content of the
database file.
Note that application-defined SQL functions or virtual tables might change the
database indirectly as a side effect. For example, if an application defines a
function "eval()" that calls sqlite3_exec(), then the following SQL
statement would change the database file through side-effects:
SELECT eval('DELETE FROM t1') FROM t2;
But because the SELECT statement does not change the database file directly,
sqlite3_stmt_readonly() would still return true.
Transaction control statements such as BEGIN, COMMIT, ROLLBACK, SAVEPOINT, and
RELEASE cause sqlite3_stmt_readonly() to return true, since the statements
themselves do not actually modify the database but rather they control the
timing of when other statements modify the database. The ATTACH and DETACH
statements also cause sqlite3_stmt_readonly() to return true since, while
those statements change the configuration of a database connection, they do
not make changes to the content of the database files on disk. The
sqlite3_stmt_readonly() interface returns true for BEGIN since BEGIN merely
sets internal flags, but the BEGIN IMMEDIATE and BEGIN EXCLUSIVE commands do
touch the database and so sqlite3_stmt_readonly() returns false for those
commands.
SEE ALSO
sqlite3_create_function(3),
sqlite3_stmt(3),
sqlite3_exec(3)