Hi All - I have 2 queries which run very different based on how I order the WHERE clause. When I put the larger filter first, it runs for 3.5 seconds. Query 1: select c5, c6, sum(sale) from sobi.sample where c5 in (5253,5110,5375,5268,5257,5266,5243,5256,5252,5361,5379,5363,5386,5367,5240,5241,5261,5249,5245,5260,5247,5264,5354,5250,5373,5366,5246,5356,5365,5255,5262,5259,5251,5369,5357,5269,5364,5380,5244,5248,5242,5254,5358,5360,5263,5362,5374,5378,5370,5294,5339,5272,5277,5275,5295,5340,5273,5276,5270,5061,5081,5079,5080,5066,5056,5073,5060,5070,5099,5101,5100,5067,5063,5077,5072,5062,5075,5083,5086,5071,5095,5058,5087,5090,5102,5084,5098,5076,5059,5074,5094,5091,5065,5069,5068,5104,5109,5107,5108,5013,5019,5022,5010,5009,5023,5011,5024,5012,5021,5007,5008,5025,5020,5055,5006,5036,5038,5054,5032,5033,5031,5039,5035,5026,5027,5030,5200,5043,5005,5041,5049,5042,5052,5040,5053,5045,5047,5048,5050,5051,5044,5046) and c6 in (5182) group by c5, c6; When I reverse the order of the WHERE clause, it runs in about .4 seconds. Query 2: c5, c6, sum(sale) from sobi.sample where c6 in (5182) and c5 in (5253,5110,5375,5268,5257,5266,5243,5256,5252,5361,5379,5363,5386,5367,5240,5241,5261,5249,5245,5260,5247,5264,5354,5250,5373,5366,5246,5356,5365,5255,5262,5259,5251,5369,5357,5269,5364,5380,5244,5248,5242,5254,5358,5360,5263,5362,5374,5378,5370,5294,5339,5272,5277,5275,5295,5340,5273,5276,5270,5061,5081,5079,5080,5066,5056,5073,5060,5070,5099,5101,5100,5067,5063,5077,5072,5062,5075,5083,5086,5071,5095,5058,5087,5090,5102,5084,5098,5076,5059,5074,5094,5091,5065,5069,5068,5104,5109,5107,5108,5013,5019,5022,5010,5009,5023,5011,5024,5012,5021,5007,5008,5025,5020,5055,5006,5036,5038,5054,5032,5033,5031,5039,5035,5026,5027,5030,5200,5043,5005,5041,5049,5042,5052,5040,5053,5045,5047,5048,5050,5051,5044,5046) group by c5, c6; This in on MonetDB server v5.6.0, based on kernel v1.24.0 which I built from the super tarball. I can attach the entire trace files for each query if appropriate for the list. While I am still learning to read the trace, it looks like most of the time spent in the first query on a series of algebra.semijoin operations. Here are the excerpted lines: Query 1: [2320345 usec # _461 := algebra.semijoin(_167=<~tmp_2116>bat[:str,:oid]{8280020}, _460=<~tmp_2016>bat[:str,:oid]{142}) ] [776017 usec # _463 := algebra.semijoin(_158=<tmp_2130>bat[:oid,:str]{8280020}, _462=<~tmp_1572>bat[:oid,:str]{5135708}) ] [253551 usec # _470 := algebra.semijoin(_464=<~tmp_2116>bat[:str,:oid]{5135708}, _469=<~tmp_2016>bat[:str,:oid]{1}) ] Query 2: [412122 usec # _179 := algebra.semijoin(_167=<~tmp_2076>bat[:str,:oid]{8280020}, _178=<~tmp_2016>bat[:str,:oid]{1}) ] [ 194 usec # _181 := algebra.semijoin(_158=<tmp_2070>bat[:oid,:str]{8280020}, _180=<~tmp_1572>bat[:oid,:str]{304}) ] [ 0 usec # _470 := algebra.semijoin(_182=<~tmp_2076>bat[:str,:oid]{304}, _469=<~tmp_2016>bat[:str,:oid]{142}) ] Any assistance would be greatly appreciated. -Ross