Core Data - why is my NSPredicate not resulting in the correct SQL query?

Question

I have tried both these NSPredicates:

            let predicate = NSPredicate(format: “personID == %lld", id)
            let predicate = NSPredicate(format: “personID == %d", id)

I enabled SQL logging and saw this at the end of the SQL query:

WHERE  t0.ZPERSONID = ?

In variables view, id has a value of Int64(156), but regardless of what I put in place of id, the resulting SQL query has t0.ZPERSONID = ? for its WHERE clause. Because of this, the predicate is useless and I’m getting duplicate record insertions every time. How do I get t0.ZPERSONID = 156?

you can check values also there in the log, but all values will be together comma separated you can put them in above query — Varun Naharia
– Varun Naharia, Commented May 11, 2017 at 9:32
@VarunNaharia I'm sorry, but I don't understand what you meant by that comment. What log are you referring to and where do I see these values? — Questioner
– Questioner, Commented May 11, 2017 at 9:34
@VarunNaharia The only thing SQL logging added to the console log in Xcode is that one query, of which I posted the WHERE clause. There's nothing else. — Questioner
– Questioner, Commented May 11, 2017 at 9:37
@Questioner: Set the Core Data debug level to 3 (see stackoverflow.com/a/12306537/1187415) and then you'll see what values the SQLite query is bound to. — Martin R
– Martin R, Commented May 11, 2017 at 9:39
That means that query is "WHERE t0.ZPERSONID = 2595". – If id is an Int64 then NSPredicate(format: "personID == %lld", id) should be correct. What does print(predicate) show? — Martin R
– Martin R, Commented May 11, 2017 at 9:55

Community · Accepted Answer · 2017-05-23 11:47:06Z

1

WHERE  t0.ZPERSONID = ?

is (part of) the prepared statement. To see which values the parameters are bound to, set the Core Data debugging level to 3 (compare How to print Core Data debug values?):

-com.apple.CoreData.SQLDebug 3
-com.apple.CoreData.Logging.stderr 1

Also print(predicate) is useful to check the created predicate for correctness.

In your case the problem is that you pass an NSNumber instance as argument, but the %lld format expects an Int64.

You can convert the NSNumber to an Int64

let id = NSNumber(value: Int64(156))

let p1 = NSPredicate(format: "personID == %lld", id.int64Value)
print(p1) // personID == 156

or even simpler, use the %@ format instead:

let p2 = NSPredicate(format: "personID == %@", id)
print(p2) // personID == 156

edited May 23, 2017 at 11:47

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answered May 11, 2017 at 11:15

Martin R

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