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ScyllaDB Java Driver is available under the Apache v2 License. ScyllaDB Java Driver is a fork of DataStax Java Driver. See Copyright here.
Caution
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Terms¶
A term is an expression that does not involve the value of a column. It is used:
as an argument to some selectors, for example the indices of sub-element selectors;
as the right operand of relations.
To create a term, call one of the factory methods in QueryBuilder:
Literals¶
literal() takes a Java object and inlines it as a CQL literal:
selectFrom("user").all().whereColumn("id").isEqualTo(literal(1));
// SELECT * FROM user WHERE id=1
The argument is converted according to the driver’s
default type mappings. If there is no default mapping, you
will get a CodecNotFoundException.
If you use custom codecs, you might need to inline a custom Java type. You can pass a CodecRegistry as the second argument (most likely, this will be the registry of your session):
MyCustomId myCustomId = ...;
CodecRegistry registry = session.getContext().getCodecRegistry();
selectFrom("user").all().whereColumn("id").isEqualTo(literal(myCustomId, registry));
Alternatively, you can pass a codec directly:
TypeCodec<MyCustomId> codec = ...;
selectFrom("user").all().whereColumn("id").isEqualTo(literal(myCustomId, codec));
Function calls¶
function() invokes a built-in or user-defined function. It takes a function name (optionally
qualified with a keyspace), and a list of terms that will be passed as arguments:
selectFrom("sensor_data")
.all()
.whereColumn("id").isEqualTo(bindMarker())
.whereColumn("date").isEqualTo(function("system", "currentDate"));
// SELECT * FROM sensor_data WHERE id=? AND date=system.currentdate()
Arithmetic operations¶
Terms can be combined with arithmetic operations.
| CQL Operator | Selector name |
|---|---|
a+b |
add |
a-b |
subtract |
-a |
negate |
a*b |
multiply |
a/b |
divide |
a%b |
remainder |
selectFrom("sensor_data")
.all()
.whereColumn("id").isEqualTo(bindMarker())
.whereColumn("unix_timestamp").isGreaterThan(
subtract(function("toUnixTimestamp", function("now")),
literal(3600)));
// SELECT * FROM sensor_data WHERE id=? AND unix_timestamp>tounixtimestamp(now())-3600
Operations can be nested, and will get parenthesized according to the usual precedence rules.
Type hints¶
typeHint forces a term to a particular CQL type. For instance, it could be used to ensure that an
expression uses floating-point division:
selectFrom("test")
.all()
.whereColumn("k").isEqualTo(literal(1))
.whereColumn("c").isGreaterThan(divide(
typeHint(literal(1), DataTypes.DOUBLE),
literal(3)));
// SELECT * FROM test WHERE k=1 AND c>(double)1/3
Raw CQL snippets¶
Finally, it is possible to provide a raw CQL snippet with raw(); it will get appended to the query
as-is, without any syntax checking or escaping:
selectFrom("sensor_data").all().whereColumn("id").isEqualTo(raw(" 1 /*some random comment*/"));
// SELECT * FROM sensor_data WHERE id= 1 /*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.