[PATCH 1 of 6 V3] revset: teach optimize if current expression should define/follow order
Martin von Zweigbergk
martinvonz at google.com
Tue Jun 21 13:47:46 EDT 2016
On Fri, Jun 17, 2016 at 7:45 AM, Yuya Nishihara <yuya at tcha.org> wrote:
> # HG changeset patch
> # User Yuya Nishihara <yuya at tcha.org>
> # Date 1455627736 -32400
> # Tue Feb 16 22:02:16 2016 +0900
> # Node ID defa6a51c4613a4294db3a16a3dea7b5cb6025a0
> # Parent d269e7db2f55f812c9ee1efe5626602614174df3
> revset: teach optimize if current expression should define/follow order
>
> New flag 'order' will be used to fix a couple of ordering bugs, such as:
>
> a) 'x & (y | z)' disregards the order of 'x' (issue 5100)
> b) 'x & y:z' is listed from 'y' to 'z'
> c) 'x & y' can be rewritten as 'y & x' if weight(x) > weight(y)
>
> (c) is a hidden bug of optimize(), which could be exposed if we've fixed
> (a) and (b) in a different way. (a) and (b) are not bugs of optimize(), but
> they can be addressed well in optimize() since optimize() knows the context.
It would be good to say what (a) and (b) *are* bugs of. I think (a) is
a bug in orset(). It seems easy to fix the bug there. Could you
explain why you didn't do that? Is it not actually easy (maybe I'm
mistaken), or is it too slow, or something else? (b) and (c) look very
similar. Is (b) a bug in rangeset()?
Can we also have the tests from patch 2/6 by themselves before the
other changes? That would make it clearer what is what each new patch
fixes.
>
> 'order' is tri-state. It starts with 'define', and shifts to 'follow' by
> 'x & y'. It changes back to 'define' on function call 'f(x)' or function-like
> operation 'x (f) y' because 'f' may have its own ordering requirement for 'x'
> and 'y'. The state 'any' will allow us to avoid extra cost that would be
> necessary to constrain ordering where it isn't important, 'not x'. For details,
> see also the tests added by the next patch.
>
> diff --git a/mercurial/revset.py b/mercurial/revset.py
> --- a/mercurial/revset.py
> +++ b/mercurial/revset.py
> @@ -2302,6 +2302,46 @@ methods = {
> "parentpost": p1,
> }
>
> +# Constants for ordering requirement, used in _optimize():
> +#
> +# If 'define', any future functions and operations can change the ordering of
> +# the entries in the set. If 'follow', any future functions and operations
> +# should take the ordering specified by the first operand to the '&' operator.
This was quite confusing to me. I think it was mostly the "future"
that tricked me. I saw it as future in terms of evaluation order of
the expression, but it's in terms of the call graph of optimize() or
something, right? Maybe "nested" or "deeper" instead?
> +#
> +# For instance,
> +#
> +# X & (Y | Z)
> +# ^ ^^^^^^^
> +# | follow
> +# define
> +#
> +# will be evaluated as 'or(y(x()), z(x()))', where 'x()' can change the order
> +# of the entries in the set, but 'y()', 'z()' and 'or()' shouldn't.
> +#
> +# 'any' means the order doesn't matter. For 'not X', 'x()' may change the
> +# order of the entries in the initial set. So for 'not (x | y)', we don't
> +# have to fix the result of 'or()' to enforce the ordering requirement.
> +# Also, 'not sort(x)' can be optimized to 'not x'.
> +#
> +# Transition of ordering requirement:
> +#
> +# 1. starts with 'define'
> +# 2. shifts to 'follow' by 'x & y'
> +# 3. changes back to 'define' on function call 'f(x)' or function-like
> +# operation 'x (f) y' because 'f' may have its own ordering requirement
> +# for 'x' and 'y' (e.g. 'first(x)')
> +#
> +_anyorder = 'any' # don't care the order
> +_defineorder = 'define' # should define the order
> +_followorder = 'follow' # must follow the current order
> +
> +# transition table for 'x & y', from the current expression 'x' to 'y'
> +_tofolloworder = {
> + _anyorder: _anyorder,
> + _defineorder: _followorder,
> + _followorder: _followorder,
> +}
> +
> def _matchonly(revs, bases):
> """
> >>> f = lambda *args: _matchonly(*map(parse, args))
> @@ -2317,7 +2357,11 @@ def _matchonly(revs, bases):
> and getstring(bases[1][1], _('not a symbol')) == 'ancestors'):
> return ('list', revs[2], bases[1][2])
>
> -def _optimize(x, small):
> +def _optimize(x, small, order):
> + """
> + 'order' specifies how the current expression 'x' is ordered (see the
> + constants defined above)
> + """
> if x is None:
> return 0, x
>
> @@ -2327,30 +2371,32 @@ def _optimize(x, small):
>
> op = x[0]
> if op == 'minus':
> - return _optimize(('and', x[1], ('not', x[2])), small)
> + return _optimize(('and', x[1], ('not', x[2])), small, order)
> elif op == 'only':
> t = ('func', ('symbol', 'only'), ('list', x[1], x[2]))
> - return _optimize(t, small)
> + return _optimize(t, small, order)
> elif op == 'onlypost':
> - return _optimize(('func', ('symbol', 'only'), x[1]), small)
> + return _optimize(('func', ('symbol', 'only'), x[1]), small, order)
> elif op == 'dagrangepre':
> - return _optimize(('func', ('symbol', 'ancestors'), x[1]), small)
> + return _optimize(('func', ('symbol', 'ancestors'), x[1]), small, order)
> elif op == 'dagrangepost':
> - return _optimize(('func', ('symbol', 'descendants'), x[1]), small)
> + t = ('func', ('symbol', 'descendants'), x[1])
> + return _optimize(t, small, order)
> elif op == 'rangeall':
> - return _optimize(('range', ('string', '0'), ('string', 'tip')), small)
> + t = ('range', ('string', '0'), ('string', 'tip'))
> + return _optimize(t, small, order)
> elif op == 'rangepre':
> - return _optimize(('range', ('string', '0'), x[1]), small)
> + return _optimize(('range', ('string', '0'), x[1]), small, order)
> elif op == 'rangepost':
> - return _optimize(('range', x[1], ('string', 'tip')), small)
> + return _optimize(('range', x[1], ('string', 'tip')), small, order)
> elif op == 'negate':
> s = getstring(x[1], _("can't negate that"))
> - return _optimize(('string', '-' + s), small)
> + return _optimize(('string', '-' + s), small, order)
> elif op in 'string symbol negate':
> return smallbonus, x # single revisions are small
> elif op == 'and':
> - wa, ta = _optimize(x[1], True)
> - wb, tb = _optimize(x[2], True)
> + wa, ta = _optimize(x[1], True, order)
> + wb, tb = _optimize(x[2], True, _tofolloworder[order])
> w = min(wa, wb)
>
> # (::x and not ::y)/(not ::y and ::x) have a fast path
> @@ -2376,12 +2422,12 @@ def _optimize(x, small):
> else:
> s = '\0'.join(t[1] for w, t in ss)
> y = ('func', ('symbol', '_list'), ('string', s))
> - w, t = _optimize(y, False)
> + w, t = _optimize(y, False, order)
> ws.append(w)
> ts.append(t)
> del ss[:]
> for y in x[1:]:
> - w, t = _optimize(y, False)
> + w, t = _optimize(y, False, order)
> if t is not None and (t[0] == 'string' or t[0] == 'symbol'):
> ss.append((w, t))
> continue
> @@ -2399,34 +2445,34 @@ def _optimize(x, small):
> # Optimize not public() to _notpublic() because we have a fast version
> if x[1] == ('func', ('symbol', 'public'), None):
> newsym = ('func', ('symbol', '_notpublic'), None)
> - o = _optimize(newsym, not small)
> + o = _optimize(newsym, not small, order)
> return o[0], o[1]
> else:
> - o = _optimize(x[1], not small)
> + o = _optimize(x[1], not small, _anyorder)
> return o[0], (op, o[1])
> elif op == 'parentpost':
> - o = _optimize(x[1], small)
> + o = _optimize(x[1], small, _defineorder)
> return o[0], (op, o[1])
> elif op == 'group':
> - return _optimize(x[1], small)
> + return _optimize(x[1], small, order)
> elif op in 'dagrange range parent ancestorspec':
> if op == 'parent':
> # x^:y means (x^) : y, not x ^ (:y)
> post = ('parentpost', x[1])
> if x[2][0] == 'dagrangepre':
> - return _optimize(('dagrange', post, x[2][1]), small)
> + return _optimize(('dagrange', post, x[2][1]), small, order)
> elif x[2][0] == 'rangepre':
> - return _optimize(('range', post, x[2][1]), small)
> -
> - wa, ta = _optimize(x[1], small)
> - wb, tb = _optimize(x[2], small)
> + return _optimize(('range', post, x[2][1]), small, order)
> +
> + wa, ta = _optimize(x[1], small, _defineorder)
> + wb, tb = _optimize(x[2], small, _defineorder)
> return wa + wb, (op, ta, tb)
> elif op == 'list':
> - ws, ts = zip(*(_optimize(y, small) for y in x[1:]))
> + ws, ts = zip(*(_optimize(y, small, order) for y in x[1:]))
> return sum(ws), (op,) + ts
> elif op == 'func':
> f = getstring(x[1], _("not a symbol"))
> - wa, ta = _optimize(x[2], small)
> + wa, ta = _optimize(x[2], small, _defineorder)
> if f in ("author branch closed date desc file grep keyword "
> "outgoing user"):
> w = 10 # slow
> @@ -2446,7 +2492,7 @@ def _optimize(x, small):
> return 1, x
>
> def optimize(tree):
> - _weight, newtree = _optimize(tree, small=True)
> + _weight, newtree = _optimize(tree, small=True, order=_defineorder)
> return newtree
>
> # the set of valid characters for the initial letter of symbols in
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