Re: [rules-users] @Rete Experts: the finer meshes of matching

On 08/04/2010 19:56, Wolfgang Laun wrote: Drools will iterate to find the first == constraints, both literal and vairable constraints. So if != or < are first, that doesn't matter. For multiple literal constraints, should definitely have the strongest descriminator first - although it's not quite that simple. You also want the descriminator that provides the highest chances of node share amoung. == literal constraints are hashed so the wider the want out (alternative values) the more scalable performance you'll see. Drools actually attempts to hash the fanout of consequence child nodes in the alpha network, if they to are ==, but rarely is there any real gain from this as after the first level of descrimination there is general not a consequence wide fanout based on the previous constraints value. There are deterministic algorithms that claim to analyse a network to re-order literal constraints to maximise node sharing, but that's not something we have, patches please :) If it's a variable constraint we support composite indexing. Drools produces a composite index based on the first 3 == constraints. Whether the order of those first 3 impacts perf, not sure. But if there was a 4th variable constraint and that was the strongest descriminator, it would get left out of the index; when in reality it's probably the most important constraint as part of the index. Mark