[PATCH 1 of 2 V5] delta: have a native implementation of _findsnapshot

[Yuya Nishihara]

On Wed, 02 Jan 2019 12:33:25 +0100, Boris Feld wrote:
> # HG changeset patch
> # User Boris Feld <boris.feld at octobus.net>
> # Date 1545297320 -3600
> #      Thu Dec 20 10:15:20 2018 +0100
> # Node ID aef438c9ecdbae3efb5f57f56041109cd5acda39
> # Parent  9e593db5f1a1b08f812591439c831ace55bca321
> # EXP-Topic sparse-revlog
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> #              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r aef438c9ecdb
> delta: have a native implementation of _findsnapshot
> 
> The function might traverse a lot of revision, a native implementation get
> significantly faster.
> 
> example affected manifest write
> before: 0.114989
> after:  0.067141 (-42%)
> 
> diff --git a/mercurial/cext/revlog.c b/mercurial/cext/revlog.c
> --- a/mercurial/cext/revlog.c
> +++ b/mercurial/cext/revlog.c
> @@ -1050,6 +1050,75 @@ static PyObject *index_issnapshot(indexO
>  	return PyBool_FromLong((long)issnap);
>  }
>  
> +static PyObject *index_findsnapshots(indexObject *self, PyObject *args)
> +{
> +	Py_ssize_t start_rev;
> +	PyObject *cache;
> +	Py_ssize_t base;
> +	Py_ssize_t rev;
> +	int issnap;
> +	PyObject *key = NULL;
> +	PyObject *allvalues = NULL;
> +	PyObject *value = NULL;

Nit: several variables can be moved inside the "for" loop.

> +	for (rev = start_rev; rev < length; rev++) {

> +		Py_CLEAR(key);
> +		Py_CLEAR(value);
> +		allvalues = NULL;

and we won't have to nullify the allvalues if it's declared inside the loop.

> +	}
> +	Py_INCREF(Py_None);
> +	return Py_None;

Py_RETURN_NONE;

> +bail:
> +	Py_XDECREF(key);
> +	Py_XDECREF(value);
> +	Py_RETURN_NONE;

return NULL;

> +}