Fraudulent
发表于 2025-3-25 06:55:58
Single Table Selectivity,ardinality) when the predicates involve columns containing data sets that are not independent of each other..Queries involving in-lists display some idiosyncratic behavior. The treatment of “in” and “not in” are self-consistent (and wrong) in 8.. The treatment of “in” is corrected in 9. and 10., but
anaerobic
发表于 2025-3-25 07:40:29
Simple B-tree Access,shed towards to the end of the index definition; otherwise your query could end up doing a lot of work with index leaf blocks. The optimizer’s cost calculation will reflect this, and may result in the index being ignored in favor of alternative paths..System statistics should be enabled as part of y
enmesh
发表于 2025-3-25 15:11:29
The Clustering Factor,owing that the real functionality of the index relies on a subset of the columns. If necessary, build the reduced index on the backup data set, generate the correct clustering_factor, and transfer it to the production index..Adjusting the clustering_factor really isn’t hacking or cheating; it is sim
变白
发表于 2025-3-25 19:13:09
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maudtin
发表于 2025-3-25 22:03:33
Hash Joins,sizes with CPU costing enabled. This fails to produce an appropriate cost for multipass joins, but does produce good costs for onepass and optimal joins..Despite the apparent niceness of the manual hash_area_size with CPU costing, the strategic option is to set the workarea_size_policy to auto, and
subacute
发表于 2025-3-26 01:23:47
Book 2006g your SQL...The cost-based optimizer is simply a piece of code that contains a model of how Oracle databases work. By applying this model to the statistics about your data, the optimizer tries to efficiently convert your query into an executable plan. Unfortunately, the model can‘t be perfect, your
white-matter
发表于 2025-3-26 04:32:36
ow Oracle databases work. By applying this model to the statistics about your data, the optimizer tries to efficiently convert your query into an executable plan. Unfortunately, the model can‘t be perfect, your978-1-59059-636-4978-1-4302-0087-1
Tartar
发表于 2025-3-26 08:40:59
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巨硕
发表于 2025-3-26 12:38:17
Single Table Selectivity,ultiplies it by the number of input rows..For a predicate on a single column, the optimizer uses either the number of distinct values or the density as the basis for calculating the selectivity of an equality predicate. For range-based predicates on a single column the optimizer bases the selectivit
plasma-cells
发表于 2025-3-26 16:59:51
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