Class: Higgs::MVCCCache
- Inherits:
-
Object
show all
- Extended by:
- Forwardable
- Defined in:
- lib/higgs/cache.rb
Overview
cache for Multi-Version Concurrency Control
Defined Under Namespace
Classes: Snapshot
Instance Method Summary
collapse
Constructor Details
Returns a new instance of MVCCCache.
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# File 'lib/higgs/cache.rb', line 117
def initialize
@lock = Mutex.new
@snapshots = {}
end
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Instance Method Details
#ref_count_down(cnum) ⇒ Object
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# File 'lib/higgs/cache.rb', line 168
def ref_count_down(cnum)
@lock.synchronize{
@snapshots[cnum][:ref_count] -= 1
@snapshots.delete(cnum) if (@snapshots[cnum][:ref_count] == 0)
}
nil
end
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#ref_count_up(cnum_func) ⇒ Object
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# File 'lib/higgs/cache.rb', line 159
def ref_count_up(cnum_func)
@lock.synchronize{
cnum = cnum_func.call
@snapshots[cnum] = { :lock => ReadWriteLock.new, :cache => {}, :ref_count => 0 } unless (@snapshots.key? cnum)
@snapshots[cnum][:ref_count] += 1
return cnum, @snapshots[cnum][:lock].read_lock, @snapshots[cnum][:cache]
}
end
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#transaction(cnum_func) ⇒ Object
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# File 'lib/higgs/cache.rb', line 261
def transaction(cnum_func)
r = nil
snapshot = Snapshot.new(self)
snapshot.ref_count_up(cnum_func)
begin
r = yield(snapshot)
ensure
snapshot.ref_count_down
end
r
end
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#write_old_values(cnum, write_list) ⇒ Object
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# File 'lib/higgs/cache.rb', line 125
def write_old_values(cnum, write_list)
snapshot_list = @lock.synchronize{ @snapshots.values }
for snapshot in snapshot_list
@snapshots.each_value do |snapshot|
lock = snapshot[:lock].write_lock
cache = snapshot[:cache]
lock.synchronize{
for ope, key, type, value in write_list
case (ope)
when :value
if (cache.key? key) then
if (cache[key] != :none && ! (cache[key].key? type)) then
cache[key][type] = { :value => value, :cnum => cnum }
end
else
cache[key] = { type => { :value => value, :cnum => cnum } }
end
when :none
unless (cache.key? key) then
cache[key] = :none
end
else
raise "unknown operation: #{ope}"
end
end
}
end
end
nil
end
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