Database Performance at Scale by Felipe Cardeneti Mendes & Piotr Sarna & Pavel Emelyanov & Cynthia Dunlop

Author:Felipe Cardeneti Mendes & Piotr Sarna & Pavel Emelyanov & Cynthia Dunlop
Language: eng
Format: epub
ISBN: 9781484297117
Publisher: Apress

Examples

Let’s take a look at a few examples of user-defined functions. The function serving as the example operates on floating point numbers; given two parameters, it returns the sum of them, inverted. Given 5 and 7, it should return 1/5+1/7, which is approximately 0.34285714285.

Here’s how it could be defined in Apache Cassandra, which allows user-defined function definitions to be provided in Java, its native language, as well as in other languages: CREATE OR REPLACE FUNCTION add_inverse(val1 double, val2 double)

RETURNS NULL ON NULL INPUT

RETURNS double LANGUAGE java

AS '

return (val1 == 0 || val2 == 0)

? Double.NaN

: (1/val1 + 1/val2);

';

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