Querying Nested Slices? about bolthold

[timshannon]

I'm going to re-open this to track adding some better slice query options. Off the top of my head I'm thinking:

• Where("SliceField").ContainsAny(value1, value2, value3)
• Where("SliceField").ContainsAll(value1, value2, value3)

Any other ideas?

[mattgrayson]

Either Contains or ContainsAll sounds reasonable. That said, while ContainsAll is more explicit in indicating what is being checked, it does read a bit awkwardly when only checking for a single value. So, I think you could make a case for all three variants (Contains, ContainsAll, and ContainsAny).

[timshannon]

#63

[timshannon]

SubQuery wouldn't be useful in this situation. Subquery would be useful if you wanted to run another separate query for each of the results of the MatchFuncQuery.

Using the comparer interface would remove the need for hte loop, but that same loop is essentially happening in the .In(...) query criteria, so go which whichever is clearer.

[timshannon]

There aren't any specific methods for slices yet, but I'd definitely consider adding some. Until then, you can use matchFunc to query slices in any way you want.

…

On Thu, Jul 4, 2019, 12:11 PM Matt Grayson ***@***.***> wrote: Apologies if this is obvious, but I couldn't find it documented anywhere and none of the available query operators seemed to cover the use case of querying nested slices. Is there a recommended approach for querying a nested slice? For example, how would I find all ItemTests that include a Tags slice containing "sausage"? var data := []ItemTest{ ItemTest{ Key: 1, ID: 32, Name: "pizza", Tags: []string{"cheese", "sausage"}, }, ItemTest{ Key: 1, ID: 32, Name: "pizza", Tags: []string{"cheese", "sausage", "pepperoni"}, }, ItemTest{ Key: 1, ID: 32, Name: "pizza", Tags: []string{"cheese", "pepperoni"}, } } — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#60?email_source=notifications&email_token=AAKE2NKNHI3CV4OPUCQP3A3P5YVMHA5CNFSM4H55S5HKYY3PNVWWK3TUL52HS4DFUVEXG43VMWVGG33NNVSW45C7NFSM4G5NN2EA>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAKE2NN5LLY3OKW2ZRZWIHTP5YVMHANCNFSM4H55S5HA> .

[mattgrayson]

Makes sense - thanks!

[mh-cbon]

I was precisely looking for this functionality.

Its not so clear what ContainsAll means. is it like an hypothetic ContainsSome or is a somehow "stricter" equality ?

[timshannon]

@mh-cbon I was trying to match the strings package. They have .Contains and .ContainsAny. I thought ContainsAll was clearer than just Contains

val := struct {
    Set []string
}{
    Set: []string{"1", "2", "3"},
}
bh.Where("Set").ContainsAll("1", "3") //true
bh.Where("Set").ContainsAll("1", "3", "4") //false
bh.Where("Set").ContainsAny("1", "7", "4") //true

Maybe it'll be simpler and clearer to only have .Contains that accepts one value, and people can use and / or to do the same:

val := struct {
    Set []string
}{
    Set: []string{"1", "2", "3"},
}
bh.Where("Set").Contains("1").And("Set").Contains("3") //true
bh.Where("Set").Contains("1").And("Set").Contains("3").And("Set").Contains("4") //false
bh.Where("Set").Contains("1").Or(bh.Where("Set").Contains("7")).Or(bh.Where("Set").Contains("4")) //true

More verbose, but clearer, which is guess in the end is more like idiomatic Go. After typing all of that up, I'm leaning towards this 2nd option.

Thoughts?

[Kvaz1r]

Why don't have both option? Contains for single parameter and ContainsAny{All} for several?

[timshannon]

I would expect having even more options would make things even less clear. The fact the @mh-cbon was confused that ContainsAll means the wording I chose was less than clear.

[mh-cbon]

second option is no-go in my opinion it just makes things harder.

First version is much better, it makes sense with insights about the design.

However, does the lib handle a strict Eq equality over basics slice types ? I mean does the And(f).Eq([]T{1,2,3}) works and returns true ? That was what bothered me about the {All}, at first i could not determine how it behaves in comparison to Eq.

[timshannon]

Equality of slices (or any field for that matter) works exactly like it does in Go. There's no magic going on in the background.

…

On Mon, Jul 8, 2019 at 9:11 AM mh-cbon ***@***.***> wrote: second option is no-go in my opinion it just makes things harder. First version is much better, it makes sense with insights about the design. However, does the lib handle a strict Eq equality over basics slice types ? I mean does the And(f).Eq([]T{1,2,3}) works and returns true ? That was what bothered me about the {All}, at first i could not determine how it behaves in comparison to Eq. — You are receiving this because you were assigned. Reply to this email directly, view it on GitHub <#60?email_source=notifications&email_token=AAKE2NO45OKEKKJALKMEW2TP6NDJJA5CNFSM4H55S5HKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODZNGTBQ#issuecomment-509241734>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAKE2NOLGI3OFDO7MZM2FCDP6NDJJANCNFSM4H55S5HA> .

-- Tim Shannon solutions.townsourced.com

[timshannon]

Also, @mh-cbon what specifically is "harder". That you have to type more or that it's less clear?

[mh-cbon]

both. harder to read, harder to build. It does not look like a good api. the first version was unclear to me at first, but that is what documentation and examples are made for.

[timshannon]

Is ContainsEach("1", "2", "3") clearer than ContainsAll("1","2", "3")?

[mh-cbon]

I think ContainsAll / ContainsAny are perfect.

[timshannon]

FYI, when using Contains/All/Any on a value other than a slice, I plan on simply not matching instead of returning a error.

[timshannon]

Details are in the README:

https://github.com/timshannon/bolthold#slices-in-structs-and-queries

[muety]

What if the slice's values are not primitives, but structs again, whose fields I want to compare to?
For instance, assume the above example is modified like this:

type Tag struct {
    Id int,
    Name string
}

// [...]
ItemTest{
    Key:  1,
    ID:   32,
    Name: "pizza",
    Tags: []Tag{Tag{Id: 1, Name: "cheese"}, Tag{Id: 2, Name: "sausage"}},
}
// [...]

Probably I can use .MatchFunc() for this, but I'm not sure how. Could somebody please give me a little support?

[timshannon]

Yeah Match Func would work, or you could implement the Comparer interface on your Tag struct:

func (t Tag) Compare(other interface{}) (int, error) {
	if t.Id == other.(Tag).Id {
		return 0, nil
	}

	if t.Id < other.(Tag).Id {
		return -1, nil
	}
	return 1, nil
}

The code above assumes you want to compare based on Tag ID.

[muety]

Very cool, thanks! I achieved what I wanted with MatchFunc using the following code.

q.Where("Tags").MatchFunc(func(ra *bolthold.RecordAccess) (bool, error) {
	if field := ra.Field(); field != nil {
		for _, item := range field.([]*Tag) {
			if item.Id == "foo" {
				return true, nil
			}
		}
		return false, nil
	}
})

However, I was wondering if I could also use .SubQuery() instead of manually iterating the slice. Could you provide some minimal documentation for that?