Nadav Har'El created CASSANDRA-21745:
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Summary: INSERT JSON and fromJson() inconsistently accept an empty
string as a value of non-string types
Key: CASSANDRA-21745
URL: https://issues.apache.org/jira/browse/CASSANDRA-21745
Project: Apache Cassandra
Issue Type: Bug
Reporter: Nadav Har'El
In INSERT JSON and in the fromJson() function, a JSON string can be used as the
value of many non-string types - e.g., "123" for an {{int}} column. But the
*empty* string {{""}} is handled inconsistently between types: for some types
it is silently accepted and writes an "empty value" (a zero-length value,
different from null), and for other types it is rejected.
Tested on Cassandra 5.0.9 and 6.0-alpha2 (same behavior), with a table having
one column of each type, using
INSERT INTO t JSON '\{"k": 1, "v": ""}'
and
{{{}INSERT INTO t (k, v) VALUES (1, fromJson('""')){}}}:
||Type||INSERT JSON with ""||fromJson('""')||
|int, bigint, boolean, decimal, double, float, uuid, timeuuid|accepted (empty
value)|accepted (empty value)|
|smallint, tinyint, duration|accepted (empty value)|server error
(RuntimeException, see below)|
|varint|InvalidRequest ("Value '' is not a valid representation of a varint
value")|FunctionFailure|
|blob|InvalidRequest|FunctionFailure|
An empty string is not a valid integer, float, UUID or boolean, so I think it
should be rejected for all these types, as it already is for {{varint}} and
{{blob}} - the user most likely made a mistake, and almost certainly didn't
intend to write an empty value. As CASSANDRA-8354 explains, empty values of
these types exist only for historical reasons and are a nuisance; they
shouldn't be this easy to write by accident.
The server errors for smallint, tinyint and duration happen because fromJson()
returns an empty value, which these types don't accept, so FunctionCall's check
of the return value throws a RuntimeException ("Return of function
system.fromjson : (text) -> smallint () is not a valid value for its declared
return type smallint") - an instance of CASSANDRA-18484.
The same behavior for date, time, inet and timestamp (which also have string
literal forms) may deserve a separate discussion: on the tested versions, "" is
rejected for date and time but accepted for inet and timestamp.
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