In(..) clause with empty collection has no affect #516

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lunny · 2017-01-06T01:07:44Z

ethantkoenig commented

2017-01-06 01:07:44 +00:00

(Migrated from github.com)

If I do something like engine.In("my_column", []int64{}).Find(&results), every row of the corresponding table will be returned (just like engine.Find(&results)). I would instead expect no rows to be returned, since a SQL query with an empty IN clause, such as SELECT * FROM foo WHERE col in (SELECT 0 WHERE 0=1) returns no rows.

If this is a bug, I would be happy to fix it.

If I do something like `engine.In("my_column", []int64{}).Find(&results)`, every row of the corresponding table will be returned (just like `engine.Find(&results)`). I would instead expect no rows to be returned, since a SQL query with an empty `IN` clause, such as `SELECT * FROM foo WHERE col in (SELECT 0 WHERE 0=1)` returns no rows. If this is a bug, I would be happy to fix it.

lunny commented

2017-01-06 01:24:14 +00:00

Yes, I know this. Keep it no condition or a false condition for empty In which one is better?

Yes, I know this. Keep it no condition or a false condition for empty `In` which one is better?

ethantkoenig commented

2017-01-06 02:01:35 +00:00

(Migrated from github.com)

I personally prefer false condition; I think that is the behavior that most users would expect.

localvar commented

2017-02-07 02:19:21 +00:00

(Migrated from github.com)

agree with @ethantkoenig , false condition make sense.

the 2nd parameter of In (the array) may be generated by program code, in this case, if keep current behavior, I have to write code like below:

if len(arr) == 0 {
    // process empty result
} else {
   // normal processing
}

but if make it false condition, client side code could be simplified to exclude if & else.

agree with @ethantkoenig , false condition make sense. the 2nd parameter of `In` (the array) may be generated by program code, in this case, if keep current behavior, I have to write code like below: ```go if len(arr) == 0 { // process empty result } else { // normal processing } ``` but if make it false condition, client side code could be simplified to exclude `if` & `else`.

lunny referenced this issue from a commit

2020-03-09 02:52:44 +00:00

fix #516, #536

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Reference: xorm/xorm#516