Joey Lynch created CASSANDRA-20102:
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Summary: Support simple length functions for blob and string
Key: CASSANDRA-20102
URL: https://issues.apache.org/jira/browse/CASSANDRA-20102
Project: Cassandra
Issue Type: Improvement
Components: CQL/Semantics
Reporter: Joey Lynch
Assignee: Joey Lynch
A common question from users is how to query for the length of {{blob}} and
{{text}} columns, and the answer is often for users to enable UDFs and then
write their own
([1|https://stackoverflow.com/questions/49674114/cassandra-query-string-length],
[2|https://stackoverflow.com/questions/58401750/how-can-i-get-size-of-blob-column-of-cassandra-using-user-defined-functions],
...). I think it would make sense for Cassandra to support a subset of the
SQL99 [binary length
functions|https://sql-99.readthedocs.io/en/latest/chapters/05.html#octet-length-expression]
and a UTF8 codepoint aware `length` function similar to PostgreSQL's
[{{length}}|https://www.postgresql.org/docs/9.1/functions-string.html] function.
Specifically I propose two new system functions:
# {{octetlength}} - Defined on all types and returns the number of underlying
bytes in the bytebuffer representation of the column.
# {{length}} - Defined on UTF8 strings, and returns the number of UTF8
codepoints in the string, equivalent to Java's
[{{String.length}}|https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/String.html#length()]
function.
Patch coming shortly. Particularly interested in feedback if we A) think these
functions are reasonable to have inside Cassandra, and B) like the names of the
functions to align with SQL or if we want to go nonstandard and do like
{{blength}} instead of octet length.
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