US 2009/0024571 A1Published application

Supporting aggregate expressions in query rewrite

AssigneeOracle International Corporation

InventorsMurali Thiyagarajan, Praveen Kumar

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Abstract

In one embodiment, a plurality of materialized views is stored, where each view includes a set of aggregate expressions. Storing each materialized view comprises identifying one or more disjuncts in the set of aggregate expressions, generating a set of disjunct trees that represent the set of aggregate expressions, and storing the set of disjunct trees. When a query that requests aggregated data is received, one or more disjuncts are identified in an aggregate expression specified in the query. A disjunct tree for the disjuncts in the query is generated. Based on the disjunct tree for the query and on the set of disjunct trees for each materialized view, a particular materialized view is determined from the plurality of materialized views. The query is rewritten into an equivalent query that references the particular materialized view, where the equivalent query would retrieve the requested aggregated data from the particular materialized view.

Claims22

Dependent claims

A computer-implemented method for rewriting queries, the method comprising:

storing a plurality of materialized views, wherein each materialized view of the plurality of materialized views includes a set of aggregate expressions, and wherein storing said each materialized view comprises:
identifying first one or more disjuncts in the set of aggregate expressions;
generating, based on the first one or more disjuncts, a set of disjunct trees that represent the set of aggregate expressions;
and
storing the set of disjunct trees in computer data storage;
receiving a query that requests aggregated data, wherein the query comprises an aggregate expression that specifies how the aggregated data is to be computed;
identifying second one or more disjuncts in the aggregate expression;
generating, based on the second one or more disjuncts, a disjunct tree that represents the aggregate expression;
based on the disjunct tree and on the set of disjunct trees associated with said each materialized view of the plurality of materialized views, determining a particular materialized view from the plurality of materialized views that stores the aggregated data specified by the aggregate expression;
and
rewriting the query into an equivalent query that references the particular materialized view, wherein the equivalent query when executed would retrieve the aggregated data from the particular materialized view.

8 more elements

A computer-readable medium storing one or more sequences of instructions for rewriting queries, which instructions when executed by one or more processors cause:

storing a plurality of materialized views, wherein each materialized view of the plurality of materialized views includes a set of aggregate expressions, and wherein storing said each materialized view comprises:
identifying first one or more disjuncts in the set of aggregate expressions;
generating, based on the first one or more disjuncts, a set of disjunct trees that represent the set of aggregate expressions;
and
storing the set of disjunct trees in computer data storage;
receiving a query that requests aggregated data, wherein the query comprises an aggregate expression that specifies how the aggregated data is to be computed;
identifying second one or more disjuncts in the aggregate expression;
generating, based on the second one or more disjuncts, a disjunct tree that represents the aggregate expression;
based on the disjunct tree and on the set of disjunct trees associated with said each materialized view of the plurality of materialized views, determining a particular materialized view from the plurality of materialized views that stores the aggregated data specified by the aggregate expression;
and
rewriting the query into an equivalent query that references the particular materialized view, wherein the equivalent query when executed would retrieve the aggregated data from the particular materialized view.

8 more elements

Dependencies are inferred from the claim text.