condition

Conditions

A condition is a clause that appears after the IF keyword in a conditional UPDATE or DELETE statement.

The easiest way to add a condition is with an ifXxx method in the fluent API:

deleteFrom("user")
    .whereColumn("k").isEqualTo(bindMarker())
    .ifColumn("v1").isEqualTo(literal(1))
    .ifColumn("v2").isEqualTo(literal(2));
// DELETE FROM user WHERE k=? IF v1=1 AND v2=2    

You can also create it manually with one of the factory methods in Condition, and then pass it to if_():

import static com.datastax.oss.driver.api.querybuilder.QueryBuilder.*;

Condition vCondition = Condition.column("v").isEqualTo(literal(1));
deleteFrom("user")
    .whereColumn("k").isEqualTo(bindMarker())
    .if_(vCondition);
// DELETE FROM user WHERE k=? IF v=1

If you call if_() multiple times, the clauses will be joined with the AND keyword. You can also add multiple conditions in a single call. This is a bit more efficient since it creates less temporary objects:

deleteFrom("user")
    .whereColumn("k").isEqualTo(bindMarker())
    .if_(
        Condition.column("v1").isEqualTo(literal(1)), 
        Condition.column("v2").isEqualTo(literal(2)));
// DELETE FROM user WHERE k=? IF v1=1 AND v2=2

Conditions are composed of a left operand, an operator, and a right-hand-side term.

Simple columns

ifColumn operates on a single column. It supports basic arithmetic comparison operators:

Comparison operator	Method name
=	isEqualTo
<	isLessThan
<=	isLessThanOrEqualTo
>	isGreaterThan
>=	isGreaterThanOrEqualTo
!=	isNotEqualTo

Note: we support != because it is present in the CQL grammar but, as of Cassandra 4, it is not implemented yet.

In addition, in() can test for equality with various alternatives. You can either provide each alternative as a term:

deleteFrom("user")
    .whereColumn("k").isEqualTo(bindMarker())
    .ifColumn("v").in(bindMarker(), bindMarker(), bindMarker());
// DELETE FROM user WHERE k=? IF v IN (?,?,?)

Or bind the whole list of alternatives as a single variable:

deleteFrom("user")
    .whereColumn("k").isEqualTo(bindMarker())
    .ifColumn("v").in(bindMarker());
// DELETE FROM user WHERE k=? IF v IN ?

UDT fields

ifField tests a field in a top-level UDT (nested UDTs are not allowed):

deleteFrom("user")
    .whereColumn("k").isEqualTo(bindMarker())
    .ifField("address", "zip").isEqualTo(literal(94040));
// DELETE FROM user WHERE k=? IF address.zip=94040

It supports the same set of operators as simple columns.

Collection elements

ifElement tests an element in a top-level collection (nested collections are not allowed):

deleteFrom("product")
    .whereColumn("sku").isEqualTo(bindMarker())
    .ifElement("features", literal("color")).in(literal("red"), literal("blue"));
// DELETE FROM product WHERE sku=? IF features['color'] IN ('red','blue')

It supports the same set of operators as simple columns.

Raw snippets

You can also provide a condition as a raw CQL snippet, that will get appended to the query as-is, without any syntax checking or escaping:

deleteFrom("product")
    .whereColumn("sku").isEqualTo(bindMarker())
    .ifRaw("features['color'] IN ('red', 'blue') /*some random comment*/");
// DELETE FROM product WHERE sku=? IF features['color'] IN ('red', 'blue') /*some random comment*/

This should be used with caution, as it's possible to generate invalid CQL that will fail at execution time; on the other hand, it can be used as a workaround to handle new CQL features that are not yet covered by the query builder.

IF EXISTS

Finally, you can specify an IF EXISTS clause:

deleteFrom("product").whereColumn("sku").isEqualTo(bindMarker()).ifExists();
// DELETE FROM product WHERE sku=? IF EXISTS

It is mutually exclusive with column conditions: if you previously specified column conditions on the statement, they will be ignored; conversely, adding a column condition cancels a previous IF EXISTS clause.