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From "Oded Peer (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-7304) Ability to distinguish between NULL and UNSET values in Prepared Statements
Date Sun, 29 Mar 2015 08:33:56 GMT


Oded Peer updated CASSANDRA-7304:
    Attachment: 7304-05.patch

Rebased to trunk

> Ability to distinguish between NULL and UNSET values in Prepared Statements
> ---------------------------------------------------------------------------
>                 Key: CASSANDRA-7304
>                 URL:
>             Project: Cassandra
>          Issue Type: Sub-task
>            Reporter: Drew Kutcharian
>            Assignee: Oded Peer
>              Labels: cql, protocolv4
>             Fix For: 3.0
>         Attachments: 7304-03.patch, 7304-04.patch, 7304-05.patch, 7304-2.patch, 7304.patch
> Currently Cassandra inserts tombstones when a value of a column is bound to NULL in a
prepared statement. At higher insert rates managing all these tombstones becomes an unnecessary
overhead. This limits the usefulness of the prepared statements since developers have to either
create multiple prepared statements (each with a different combination of column names, which
at times is just unfeasible because of the sheer number of possible combinations) or fall
back to using regular (non-prepared) statements.
> This JIRA is here to explore the possibility of either:
> A. Have a flag on prepared statements that once set, tells Cassandra to ignore null columns
> or
> B. Have an "UNSET" value which makes Cassandra skip the null columns and not tombstone
> Basically, in the context of a prepared statement, a null value means delete, but we
don’t have anything that means "ignore" (besides creating a new prepared statement without
the ignored column).
> Please refer to the original conversation on DataStax Java Driver mailing list for more
> *EDIT 18/12/14 - [~odpeer] Implementation Notes:*
> The motivation hasn't changed.
> Protocol version 4 specifies that bind variables do not require having a value when executing
a statement. Bind variables without a value are called 'unset'. The 'unset' bind variable
is serialized as the int value '-2' without following bytes.
> \\
> \\
> * An unset bind variable in an EXECUTE or BATCH request
> ** On a {{value}} does not modify the value and does not create a tombstone
> ** On the {{ttl}} clause is treated as 'unlimited'
> ** On the {{timestamp}} clause is treated as 'now'
> ** On a map key or a list index throws {{InvalidRequestException}}
> ** On a {{counter}} increment or decrement operation does not change the counter value,
e.g. {{UPDATE my_tab SET c = c - ? WHERE k = 1}} does change the value of counter {{c}}
> ** On a tuple field or UDT field throws {{InvalidRequestException}}
> * An unset bind variable in a QUERY request
> ** On a partition column, clustering column or index column in the {{WHERE}} clause throws
> ** On the {{limit}} clause is treated as 'unlimited'

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