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.. -*- rst -*-
.. highlightlang:: c
``grn_cache``
=============
Summary
-------
.. note::
This API is experimental.
``grn_cache`` is a data store that keeps responses of
:doc:`/reference/commands/select` command. It is not general use cache
object. It is only for :doc:`/reference/commands/select` command.
You can just change the current cache object by
:c:func:`grn_cache_current_set()`. :doc:`/reference/commands/select`
command response cache is done internally.
:doc:`/reference/commands/select` command uses one global cache
object. If you open multiple databases, the one cache is shared. It is
an important problem.
If you open multiple databases and use
:doc:`/reference/commands/select` command, you need to use
``grn_cache`` object. It is :doc:`/reference/executables/groonga-httpd`
case. If you open only one database or don't use
:doc:`/reference/commands/select` command, you don't need to use
``grn_cache`` object. It is `rroonga
<http://ranguba.org/#about-rroonga>`_ case.
Example
-------
Here is an example that change the current cache object.
.. code-block:: c
grn_cache *cache;
grn_cache *cache_previous;
cache = grn_cache_open(ctx);
cache_previous = grn_cache_current_get(ctx);
grn_cache_current_set(ctx, cache);
/* grn_ctx_send(ctx, ...); */
grn_cache_current_set(ctx, cache_previous);
Reference
---------
.. c:type:: grn_cache
It is an opaque cache object. You can create a ``grn_cache`` by
:c:func:`grn_cache_open()` and free the created object by
:c:func:`grn_cache_close()`.
.. c:function:: grn_cache *grn_cache_open(grn_ctx *ctx)
Creates a new cache object.
If memory allocation for the new cache object is failed, ``NULL``
is returned. Error information is stored into the ``ctx``.
:param ctx: The context.
:return: A newly allocated cache object on success, ``NULL``
otherwise. The returned cache object must be freed by
:c:func:`grn_cache_close()`.
.. c:function:: grn_rc grn_cache_close(grn_ctx *ctx, grn_cache *cache)
Frees resourses of the ``cache``.
:param ctx: The context.
:param cache: The cache object to be freed.
:return: ``GRN_SUCCESS`` on success, not ``GRN_SUCCESS`` otherwise.
.. c:function:: grn_rc grn_cache_current_set(grn_ctx *ctx, grn_cache *cache)
Sets the cache object that is used in
:doc:`/reference/commands/select` command.
:param ctx: The context.
:param cache: The cache object that is used in
:doc:`/reference/commands/select` command.
:return: ``GRN_SUCCESS`` on success, not ``GRN_SUCCESS`` otherwise.
.. c:function:: grn_cache *grn_cache_current_get(grn_ctx *ctx)
Gets the cache object that is used in
:doc:`/reference/commands/select` command.
:param ctx: The context.
:return: The cache object that is used in
:doc:`/reference/commands/select` command. It may be ``NULL``.
.. c:function:: grn_rc grn_cache_set_max_n_entries(grn_ctx *ctx, grn_cache *cache, unsigned int n)
Sets the max number of entries of the cache object.
:param ctx: The context.
:param cache: The cache object to be changed.
:param n: The new max number of entries of the cache object.
:return: ``GRN_SUCCESS`` on success, not ``GRN_SUCCESS`` otherwise.
.. c:function:: unsigned int grn_cache_get_max_n_entries(grn_ctx *ctx, grn_cache *cache)
Gets the max number of entries of the cache object.
:param ctx: The context.
:param cache: The target cache object.
:return: The max number of entries of the cache object.
|
