来自 SET EXPLAIN 语句的 UPDATE STATISTICS 的输出

SET EXPLAIN 语句可显示 UPDATE STATISTICS 用来生成列分发的计划。下列输出是基于排序内存的缺省的 DBUPSPACE 值 15 MB，在此示例中其需要两道检验来对 21.9 MB 数据进行排序：

UPDATE STATISTICS:
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Table: zelaine.t1
Mode: HIGH
Number of Bins: 267 Bin size 2505
Sort data 21.9 MB Sort memory granted 15.0 MB
Estimated number of table scans 2
PASS #1 b
PASS #2 a
Scan 9 Sort 1 Build 2 Insert 0 Close 0 Total 12
Completed pass 1 in 0 minutes 12 seconds
Scan 5 Sort 2 Build 1 Insert 0 Close 0 Total 8
Completed pass 2 in 0 minutes 8 seconds