Estimating a number of rows returned by a recursive query

Details Estimating a number of rows returned by a recursive query Estimating a number of rows returned by a recursive query

2007-11-19

2010-11-23

Wong, Don (Department: 2163)

Data processing: database and file management or data structures

Database and file access

Record, file, and data search and comparisons

C707S773000

Reexamination Certificate

active

07840592

ABSTRACT:
A number of rows that a recursive query will retrieve from a table is estimated by recursively probing an index associated with the table. A recursive query includes a seed and a recursive predicate, each of which is associated with a respective column in the table. If the index has a leading column that matches the table column associated with the seed, and the index has a secondary column that matches the table column associated with the recursive predicate, then the index is recursively probed until a threshold depth of the recursive probing is reached or until all nodes of the index have been examined. The estimated number of rows that the recursive query will retrieve is then calculated based on either the number of rows examined in the index or based on the threshold depth, a cardinality of the secondary column, and a cardinality of the primary column.

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