Built-in query language functions

Like constants and variables, there are many built-in functions that can be called from the query language with no additional imports or setup. These built-in functions should be used over Python or other user-defined functions in query strings for two reasons:

They are almost always more performant.
They handle null values gracefully.

For more on why, see The Python-Java boundary.

Built-in functions

Built-in functions range from simple mathematical functions to date-time arithmetic, string manipulation, and more.

The following query calculates the absolute value of a column using the built-in abs function:

from deephaven import empty_table

source = empty_table(10).update(["X = -ii", "AbsX = abs(X)"])

The following query parses a column of strings containing integers into Java primitive int values using parseInt:

from deephaven import empty_table
from random import choice


def rand_string_number() -> str:
    return choice([str(item) for item in list(range(10))])


source = empty_table(10).update("StringColumn = rand_string_number()")
result = source.update("IntegerColumn = parseInt(StringColumn)")

The following query uses the built-in and function to evaluate whether or not three different columns are all true:

from deephaven import new_table
from deephaven.column import bool_col

source = new_table(
    [
        bool_col("A", [True, True, True]),
        bool_col("B", [True, True, False]),
        bool_col("C", [True, False, True]),
    ]
)
result = source.update(["IsOk = and(A, B, C)"])

Built-in functions gracefully handle null values as input. For example, the following example calls the built-in sin function on a column that contains null values:

from deephaven import empty_table

source = empty_table(40).update(
    ["X = (ii % 3 != 0) ? 0.1 * ii : NULL_DOUBLE", "SinX = sin(X)"]
)

This page does not provide a comprehensive list of all built-ins. For the complete list of functions built into the query language, see Auto-imported functions.

Add Java classes to the query library

To use a non-default Java class in a Deephaven Query Language (DQL) query string, you must first import the class into DQL using Python. For this, Deephaven offers the query_library module.

The following example adds the java.net.URL class to the query library then uses it in table operations.

from deephaven import empty_table
from deephaven import query_library

query_library.import_class("java.net.URL")

source = empty_table(1).update(
    [
        "DeephavenUrl = new URL(`https://deephaven.io/`)",
        "Protocol = DeephavenUrl.getProtocol()",
        "Host = DeephavenUrl.getHost()",
        "Path = DeephavenUrl.getPath()",
    ]
)

You can also import static methods from a class into the query language to use them in table operations. The following example imports static methods from the java.lang.StrictMath class and uses them in table operations.

Note

import_static allows you to call methods without the class name. The class name is included in the examples below because methods of the same name also exist in the built-in io.deephaven.function.Numeric class.

from deephaven import empty_table
from deephaven import query_library

query_library.import_static("java.lang.StrictMath")

source = empty_table(10).update(
    [
        "X = randomDouble(-1.67, 1.67)",
        "AcosX = StrictMath.acos(X)",
        "ExpX = StrictMath.exp(X)",
        "ExponentX = StrictMath.getExponent(X)",
    ]
)

Built-in query language functions

Built-in functions

Add Java classes to the query library

Related documentation