View matching for materialized outer-join views

A computer implemented method that facilitates view matching for outer join views, comprising:

• receiving by an interface component at least one query, the at least one query comprising at least one of a selection operator (σ), a predicate, a projection operator (π), and a join operator;
• retrieving one or more materialized view expressions;
• converting by a view-matching component the at least one received query and the one or more materialized views to a normalized query expression and a normalized view expression, wherein the converting comprising,
• converting by a normalization component the at least one query expression and at least one materialized view expression into a normalized query expression and a normalized view expression;
• receiving by an analysis component the normalized query expression and the normalized view expression, the analysis component effectuates duplicate elimination where a unique key is available by verifying that each view term σP(R) required by a term in the normalized query expression can be recovered from the normalized view through utilization of expressions of the form σP(R)=δ(πR1.*,R2.*, . . . ,Rn.*σ□null(R1)^ . . . ^□null(Rn)V), wherein R={R1, R2, . . . , Rn} is a set of source tables of a term in the normalized view V, P represents a predicate, δ denotes an operator that removes duplicates, R1.*, R2.*, . . . , Rn.* connote all columns in tables R1, R2, . . . , Rn of the normalized view, ^ represents an AND operator, and ˜null(R1) . . . ˜null(Rn) are predicates testing that the columns of R1, . . . , Rn are not null;
• and
• constructing by a construction component that constructs a substitute query expression by recovering a source term of the normalized query expression using the selection operator with an appropriate null and not null predicate and where necessary applying duplicate elimination, where necessary utilizing the selection operator with appropriate residual predicates to restrict a result, applying the projection operator without duplicate elimination to reduce the result to one or more required output columns, exploiting one or more equivalence classes, and returning null for the one or more required output columns that originate from a table not contained in a base of the term.

A computer storage medium having stored thereon computer instructions executed by a processor to facilitate view matching for outer join views, comprising:

• receiving by an interface component at least one query, the at least one query comprising at least one of a selection operator (σ), a predicate, a projection operator (π), and a join operator;
• retrieving one or more materialized view expressions;
• converting by a view-matching component the at least one received query and the one or more materialized views to a normalized query expression and a normalized view expression, wherein the converting comprising,
• converting by a normalization component the at least one query expression and at least one materialized view expression into a normalized query expression and a normalized view expression;
• receiving by an analysis component the normalized query expression and the normalized view expression, the analysis component effectuates duplicate elimination where a unique key is available by verifying that each view term σP(R) required by a term in the normalized query expression can be recovered from the normalized view through utilization of expressions of the form σP(R)=δ(πR1.*,R2.*, . . . ,Rn.*σ□null(R1)^ . . . ^□null(Rn)V), wherein R={R1, R2, . . . , Rn} is a set of source tables of a term in the normalized view V, P represents a predicate, δ denotes an operator that removes duplicates, R1.*, R2.*, . . . , Rn.* connote all columns in tables R1, R2, . . . , Rn of the normalized view, ^ represents an AND operator, and ˜null(R1) . . . ˜null(Rn) are predicates testing that the columns of R1, . . . , Rn are not null;
• and
• constructing by a construction component that constructs a substitute query expression by recovering a source term of the normalized query expression using the selection operator with an appropriate null and not null predicate and where necessary applying duplicate elimination, where necessary utilizing the selection operator with appropriate residual predicates to restrict a result, applying the projection operator without duplicate elimination to reduce the result to one or more required output columns, exploiting one or more equivalence classes, and returning null for the one or more required output columns that originate from a table not contained in a base of the term.