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==============
System ops
==============
.. module:: SysOp
:noindex:
System ops start with a double-colon ``::`` and must appear alone in a script.
In the following, we explain what each system op does, and the arguments they expect.
--------------
Explain
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.. function:: ::explain { <query> }
A single query is enclosed in curly braces. Query options are allowed but ignored.
The query is not executed, but its query plan is returned instead.
Currently, there is no specification for the return format,
but if you are familiar with the semi-naïve evaluation of stratified Datalog programs
subject to magic-set rewrites, the returned data is pretty self-explanatory.
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Ops on stored relations
----------------------------------
.. function:: ::relations
List all stored relations currently in the database
.. function:: ::columns <REL_NAME>
List all columns for the stored relation ``<REL_NAME>``.
.. function:: ::remove <REL_NAME> (, <REL_NAME>)*
Remove stored relations. Several can be specified, joined by commas.
.. function:: ::rename <OLD_NAME> -> <NEW_NAME> (, <OLD_NAME> -> <NEW_NAME>)*
Rename stored relation ``<OLD_NAME>`` into ``<NEW_NAME>``. Several may be specified, joined by commas.
.. function:: ::show_triggers <REL_NAME>
Display triggers associated with the stored relation ``<REL_NAME>``.
.. function:: ::set_triggers <REL_NAME> <TRIGGERS>
Set triggers for the stored relation ``<REL_NAME>``. This is explained in more detail in the transactions chapter.
.. function:: ::access_level <REL_NAME> <ACCESS_LEVEL>
Sets the access level of ``<REL_NAME>`` to the given level. The levels are:
* ``normal`` allows everything,
* ``protected`` disallows ``::remove`` and ``:replace``,
* ``read_only`` additionally disallows any mutations and setting triggers,
* ``hidden`` additionally disallows any data access (metadata access via ``::relations``, etc., are still allowed).
It is recommended to give the appropriate access levels to tables to prevent data loss from programming mistakes.
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Monitor and kill
------------------------------------
.. function:: ::running
Display currently running queries and their IDs.
.. function:: ::kill <ID>
Kill a running query specified by ``<ID>``. The ID may be obtained by ``::running``.
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Maintenance
------------------------------------
.. function:: ::compact
Run compaction on the database. Running this may make the database smaller on disk and faster for queries,
but running the op itself may take some time in the background.