 / Check-in [9660ce54]

 ```4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 ``` ```** ** TUNING: For every WHERE clause term that is not used by the index ** and which does not have an assigned truth probability, heuristics ** described below are used to try to estimate the truth probability. ** TODO --> Perhaps this is something that could be improved by better ** table statistics. ** ** Heuristic 1: Estimate the truth probability as 6.25%. The 6.25% ** value corresponds to 1 in LogEst notation, so this means decrement ** the WhereLoop.nOut field for every such WHERE clause term. ** ** Heuristic 2: If there exists one or more WHERE clause terms of the ** form "x==EXPR" and EXPR is not a constant 0 or 1, then make sure the ** final output row estimate is no greater than 1/4 of the total number ** of rows in the table. In other words, assume that x==EXPR will filter ** out at least 3 out of 4 rows. If EXPR is -1 or 0 or 1, then maybe the ``` ``` | | ``` ```4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 ``` ```** ** TUNING: For every WHERE clause term that is not used by the index ** and which does not have an assigned truth probability, heuristics ** described below are used to try to estimate the truth probability. ** TODO --> Perhaps this is something that could be improved by better ** table statistics. ** ** Heuristic 1: Estimate the truth probability as 93.75%. The 93.75% ** value corresponds to -1 in LogEst notation, so this means decrement ** the WhereLoop.nOut field for every such WHERE clause term. ** ** Heuristic 2: If there exists one or more WHERE clause terms of the ** form "x==EXPR" and EXPR is not a constant 0 or 1, then make sure the ** final output row estimate is no greater than 1/4 of the total number ** of rows in the table. In other words, assume that x==EXPR will filter ** out at least 3 out of 4 rows. If EXPR is -1 or 0 or 1, then maybe the ```