最近准备写点Histogram和density相关的文章，先把术语给大家理一理： cardinality (CDN) Legend CBQT - cost-based query transformation JPPD - join predicate push-down OJPPD - old-style (non-cost-based) JPPD FPD - filter push-down PM - predicate move-around CVM - complex view merging SPJ - select-project-join SJC - set join conversion SU - subquery unnesting OBYE - order by elimination OST - old style star transformation ST - new (cbqt) star transformation CNT - count(col) to count(*) transformation JE - Join Elimination JF - join factorization SLP - select list pruning DP - distinct placement qb - query block LB - leaf blocks DK - distinct keys LB/K - average number of leaf blocks per key DB/K - average number of data blocks per key CLUF - clustering factor NDV - number of distinct values Resp - response cost Card - cardinality Resc - resource cost NL - nested loops (join) SM - sort merge (join) HA - hash (join) CPUSPEED - CPU Speed IOTFRSPEED - I/O transfer speed IOSEEKTIM - I/O seek time SREADTIM - average single block read time MREADTIM - average multiblock read time MBRC - average multiblock read count MAXTHR - maximum I/O system throughput SLAVETHR - average slave I/O throughput dmeth - distribution method 1: no partitioning required 2: value partitioned 4: right is random (round-robin) 128: left is random (round-robin) 8: broadcast right and partition left 16: broadcast left and partition right 32: partition left using partitioning of right 64: partition right using partitioning of left 256: run the join in serial 0: invalid distribution method sel - selectivity ptn - partition adop Automatic degree of parallelism TABLE: Table Name ALIAS: Table Alias QBS: Query Block Signature #ROWS: Number of Rows #BLKS: Number of Blocks ARL: Average Row Length COR: Cardinality Original CRD: Cardinality Rounded CCM: Cardinality Computed CNA: Cardinality Non Adjusted AVGLEN: Average Column Length NDV: Number of Distinct Values NULLS: Number of Nulls in Column DEN: Column Density MIN: Minimum Column ValueMAX: Maximum Column Value TYPE: Histogram Type #BKTS: Histogram Buckets UNCOMPBKTS: Histogram Uncompressed Buckets
本文转自maclean_007 51CTO博客，原文链接:http://blog.51cto.com/maclean/1278510
