It is complicated to filter a table's column on several conditions

[echebbi]

The Query DSL does not allow to express easily OR conditions.

For instance, in order to keep the rows where the value of the column "A" is either null or a string in lower case, we have to write :

Query
    .select()
    .from(table)
    .where("A").asStr().match(str -> str == null || str.equals(str.toLowerCase());

The built-in methods such as isInstanceOf,in or isTrue cannot be used anymore and must be re-written by the user.

It would be better to write something like :

Query
    .select()
    .from(table)
    .where("A").isNull().or().asStr().isInLowerCase();

or even :

Query
    .select()
    .from(table)
    .where("A").asStr().match(str -> str.isNull() || str.isInLowerCase());

instead.

Either way, the current DSL makes predicate composition difficult and should be adapted.

[echebbi]

With the upcoming type-safe features, this issue will soon be resolved. Indeed, the previous code can now be written as:

private static final ColumnId<String> A = id(String.class, "a");

table.filter(row ->
    row.get(A) == null 
 || row.get(A).equals(row.get(A).toLowerCase())
);

In my opinion, it is clear enough.

The Query API should also be enhanced to support the following syntax;

Query
    .select()
    .from(table)
    .where(A).isNull().or().isInLowerCase();