[PATCH v2 1/4] schema: refactor space_cache API

[Vladimir Davydov]

On Thu, Oct 25, 2018 at 11:17:09AM +0300, Kirill Yukhin wrote:
> Remove function which deletes from cache, making replace
> more general: it might be used for both insertions,
> deletions and replaces. Also, put assert on equality
> of space pointer found in cache to old one into
> replace routine.

I guess this refactoring should be pushed to 1.10-features, right?

> ---
>  src/box/alter.cc  | 26 ++++++++++----------------
>  src/box/schema.cc | 52 +++++++++++++++++++++++++---------------------------
>  src/box/schema.h  |  9 ++-------
>  3 files changed, 37 insertions(+), 50 deletions(-)
> 
> diff --git a/src/box/alter.cc b/src/box/alter.cc
> index de3943c..79ff589 100644
> --- a/src/box/alter.cc
> +++ b/src/box/alter.cc
> @@ -1610,8 +1604,7 @@ on_drop_view_rollback(struct trigger *trigger, void *event)
>   *
>   * - space cache should be updated, and changes in the space
>   *   cache should be reflected in Lua bindings
> - *   (this is done in space_cache_replace() and
> - *   space_cache_delete())
> + *   (this is done in space_cache_replace())

This comment is obsolete. Lua bindings are updated by an on_alter_space
trigger callback. Please fix.

>   *
>   * - the space which is changed should be rebuilt according
>   *   to the nature of the modification, i.e. indexes added/dropped,
> @@ -1695,7 +1688,7 @@ on_replace_dd_space(struct trigger * /* trigger */, void *event)
>  		 * cache right away to achieve linearisable
>  		 * execution on a replica.
>  		 */
> -		(void) space_cache_replace(space);
> +		(void) space_cache_replace(NULL, space);

(void) is not needed here anymore.

>  		/*
>  		 * Do not forget to update schema_version right after
>  		 * inserting the space to the space_cache, since no
> @@ -447,8 +446,7 @@ schema_free(void)
>  
>  		struct space *space = (struct space *)
>  				mh_i32ptr_node(spaces, i)->val;
> -		space_cache_delete(space_id(space));
> -		space_delete(space);
> +		space_cache_replace(space, NULL);

space_cache_replace(), just like its predecessor space_cache_delete(),
doesn't delete the space so space_delete() must remain.

>  	}
>  	mh_i32ptr_delete(spaces);
>  	while (mh_size(funcs) > 0) {
> diff --git a/src/box/schema.h b/src/box/schema.h
> index 264c16b..05f32de 100644
> --- a/src/box/schema.h
> +++ b/src/box/schema.h
> @@ -134,14 +134,9 @@ space_cache_find_xc(uint32_t id)
>  /**
>   * Update contents of the space cache.  Typically the new space is
>   * an altered version of the original space.
> - * Returns the old space, if any.

What's the old and new spaces are for? Please improve the comment.

>   */
> -struct space *
> -space_cache_replace(struct space *space);
> -
> -/** Delete a space from the space cache. */
> -struct space *
> -space_cache_delete(uint32_t id);
> +void
> +space_cache_replace(struct space *old_space, struct space *new_space);
>  
>  void
>  schema_init();