Re: How to build Exists Expression with a sub expression on the child entity?

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Thank you Nikita, that helps me.=20

In EOF we use them in memory as well as for fetching from the database.

In Cayenne it seems that once I call exists() then the expression cannot =
be used for filtering in memory.

For example:

Expression expr =3D exp("paintings.name like 'S%'").exists();
	=09
List<Artist> someArtists =3D ObjectSelect
		.query(Artist.class)
		.where(expr)
		.select(context);

The above matches 1 artist, e.g. =E2=80=9CVincent Van Gogh=E2=80=9D who =
has a paintings starting with the letter S, e.g. Starry Night and =
Sunflowers. But when I use that same expression against a list of all =
the artists like this:

List<Artist> someArtists2 =3D expr.filterObjects(allArtists);

Then someArtists2 is empty.

However, if I rewrite the code as follows:

Expression expr =3D exp("paintings.name like 'S%'");
	=09
List<Artist> someArtists =3D ObjectSelect
		.query(Artist.class)
		.where(expr.exists())
		.select(context);

// This matches 1 artist
List<Artist> someArtists2 =3D expr.filterObjects(allArtists);



Regards,
Ricardo Parada



> On Sep 27, 2025, at 12:26=E2=80=AFPM, Nikita Timofeev =
<[email protected]> wrote:
>=20
> Hi Ricardo,
>=20
> Yeah, there's not much info on that since that's a new API. `exists()` =
is a
> terminal operator that converts the whole expression to an EXISTS =
query.
>=20
> So it would be something like this in your
> example: =
Artist.PAINTINGS.dot(Painting.NAME).like("painting%").exists()
>=20
>=20
> On Fri, Sep 26, 2025 at 8:31=E2=80=AFPM Ricardo Parada =
<[email protected]>
> wrote:
>=20
>> Hi all,
>>=20
>> Another question I have is regarding EXISTS expressions.  I=E2=80=99m =
not sure if
>> I=E2=80=99m using the API correctly, but I was thinking it would be =
something like
>> this.  Using the entities from the Tutorial, let=E2=80=99s say I want =
to fetch the
>> Artist=E2=80=99s that have a painting starting with the letter =
=E2=80=98G=E2=80=99:
>>=20
>> Expression e =3D =
Artist.PAINTINGS.exists(Painting.NAME.like(=E2=80=9CG%=E2=80=9D));
>>=20
>> But I=E2=80=99m getting a syntax error.
>=20
>=20
>=20
> --=20
> Best regards,
> Nikita Timofeev


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