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Changes in 3.0

Below is a summary of changes from V2.8. Commercially licensed users may obtain the detailed change list / release notes from (

Production release date


Vectors are no longer limited to 2 billion items as they now have a 64-bit length.

The default integer is no longer 32-bit, it is 64-bit. i.e. in k/q 0 is shorthand for 0j. 0i represents a 32-bit int.

You should almost never see type i, just like we never see type h.

The return type from count, find, floor, … are now 64-bit ints (q longs)

Schemas and q script files should be fine.

There will be some NUCs when performing operations like 0^int(), as this now returns a vector of 64-bit ints. It may be simplest to scan your code for numeric literals, and where 32-bit ints are intended to be kept, specify them explicitly as such, e.g. 0i^… This can be done prior to upgrade and such tokens are compatible with previous versions.

kdb+ 3.0 can read 2.7/2.8 kdb+ file formats without conversion. kdb+ files created by 3.0 cannot be read by previous versions.

IPC messaging is similar to previous versions, and no single message can exceed 2 billion bytes. In general, if you choose to upgrade, to ensure full IPC interop you should first upgrade your current kdb+ version to the latest release of that version (assuming versions 2.6 thru 2.8), then update client applications to use the latest drivers and then update the kdb+ version to V3.0. If you do not upgrade the drivers, you will not be able to send timestamp/timespan types to those applications, nor use IPC compression.

Shared libraries that are loaded into kdb+ must be recompiled using the new k header, and some function signatures have widened some of their types.


When compiling for V3.0, define KXVER=3, e.g. gcc -D KXVER=3 …

At the moment there's no need to recompile standalone apps, i.e. that do not load as a shared lib into kdb+. If you choose to update to the latest k.h header file, and compile with KXVER=3, ensure that you link to the latest C library (c.o/c.dll). For legacy apps that are just being maintained, you can continue to use the new header file and compile with KXVER undefined or =2, and bind with older c.o/c.obj.

  • kdb+V3.0 has support for WebSockets according to RFC 6455, and has been tested with Chrome and Firefox. It is expected that other browsers will catch up shortly.

  • A new type – Guid, type 2 – has been added. See Datatypes

  • plist has been removed.

  • date+time results in timestamp type; previously date+time resulted in datetime type, which has been deprecated since V2.6.