I'm trying to use information from sqlite3_errmsg() to figure out what
*kind* of SQLITE_CONSTRAINT happened.
Cruising the archives of this mailing list, I see past discussions about
the desire for really complete error information, including the name of
the specific constraint that failed (and ideally in a format which does
not need to be parsed or is designed to be parsed). I add my vote for
how cool that functionality would be. For now, I'm just looking for a
way to distinguish between the major types of constraint violations,
(unique, check, foreign key, etc).
I would welcome remarks from the SQLite developers on the code snippet
below.
Specific questions:
(1) What is the likelihood of future changes to the phrasing of
sqlite3_errmsg() strings?
(2) Is there any situation where (0 == strcmp(sqlite3_errmsg(db),
"constraint failed")) and the violation was NOT a CHECK constraint?
(3) Dare I hold out hope for extended error codes like the following?
#define SQLITE_CONSTRAINT_UNIQUE (SQLITE_CONSTRAINT | (1<<8) )
#define SQLITE_CONSTRAINT_FOREIGN_KEY (SQLITE_CONSTRAINT | (2<<8) )
#define SQLITE_CONSTRAINT_CHECK (SQLITE_CONSTRAINT | (3<<8) )
#define SQLITE_CONSTRAINT_NOT_NULL (SQLITE_CONSTRAINT | (4<<8) )
My code snippet:
--------
if (SQLITE_CONSTRAINT == rc)
{
const char* psz_errmsg = sqlite3_errmsg(psql);
// We're on thin ice here. sqlite doesn't make any promises about
// what the errmsg string will contain for various constraint
violations.
// Nonetheless, this works. If sqlite changes the errmsgs in the
future,
// this will break. We've got test cases to detect this.
if (strstr(psz_errmsg, "not unique"))
{
// TODO should occur at the end of the string
...
}
else if (strstr(psz_errmsg, "foreign key"))
{
// TODO could check for exact strcmp match to "foreign key
constraint failed"
...
}
else if (strstr(psz_errmsg, "constraint failed"))
{
// TODO could check for exact strcmp match to "constraint failed"
// TODO riskiest one, since sqlite doesn't say it was a check
constraint
// TODO but it seems to use a more specific phrase in all other
cases except check constraints
...
}
}
--------
Thanks!
--
E
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