Synchronization of SQL actions in a relational database system

A query optimizer system in a relational database processing system having a plurality of base tables {T} for processing queries represented by query graphs {G} wherein each said query graph G includes a plurality of nodes {N.sub.i } each representing a relational operation, wherein each said node N.sub.i receives from each of one or more other said nodes {N.sub.j } a flow of records represented by a directed data-flow arc A.sub.ji forming part of a data-flow path and wherein i, j are positive integers, said system comprising:

• means for evaluating said query graph G for each said base table T.sub.each and identifying common-referencing pairs of said nodes;
• query graph reforming means for reforming said query graph G by either (i) restricting said data-flow path between the nodes of one or more of said common-referencing pairs of nodes or (ii) inserting a sub-query node between the nodes of one or more of said common-referencing pairs of nodes, or by separately performing both (i) and (ii) on respective ones of said common-referencing pairs of nodes to sequence the execution of each said common-referencing pair of nodes to produce a query graph G.sub.MTI that enforces database integrity during table mutation;
• query plan means coupled to said data-flow restriction means for generating a plurality of query execution plans for executing said query graph G.sub.MTI ;
• and
• query evaluation means coupled to said query plan means for evaluating the execution cost of each said query execution plan and for selecting an optimal said query execution plan.

A database processing system comprising:

• a data store for storing a plurality of base tables {T};
• logical processing means for processing queries represented by query graphs {G} wherein each said query graph G includes a plurality of nodes {N.sub.i } each representing a relational operation, wherein each said node N.sub.i receives from each of one or more other said nodes {N.sub.j } a flow of records represented by a directed data-flow arc A.sub.ji forming part of a data-flow path and wherein i, j are positive integers;
• means for evaluating said query graph G for each said base table T.sub.each to identify common-referencing pairs of said nodes for which said each base table T.sub.each is the object;
• query graph reforming means for reforming said query graph G by either (i) restricting said data-flow path between the nodes of one or more of said common-referencing pairs of nodes or (ii) inserting a sub-query node between the nodes of one or more of said common-referencing pairs of nodes, or by separately performing both (i) and (ii) on respective ones of said common-referencing pairs of nodes to sequence the execution of each said common-referencing pair of nodes to produce a query graph G.sub.MTI that enforces database integrity during table mutation;
• query plan means coupled to said data-flow restriction means for generating a plurality of query execution plans for executing said query graph G.sub.MTI ;
• and
• query evaluation means coupled to said query plan means for evaluating the execution cost of each said query execution plan and for selecting an optimal said query execution plan.

A computer program product, for use with a relational database processing system having a stored database including a plurality of base tables {T} for processing queries represented by query graphs {G} wherein each said query graph G includes a plurality of nodes {N.sub.i } each representing a relational operation, wherein each said node N.sub.i receives from each of one or more other said nodes {N.sub.j } a flow of records represented by a directed data-flow arc A.sub.ji forming part of a data-flow path and wherein i and j are positive integers, said computer program product comprising:

• a recording medium;
• means, recorded on said recording medium, for causing said system to evaluate said query graph G for each said base table T.sub.each to identify common-referencing pairs of said nodes for which said each base table T.sub.each is the object;
• means, recorded on said recording medium, for causing said system to reform said query graph G to reform said query graph G by either (i) restricting said data-flow path between the nodes of one or more of said common-referencing pairs of nodes or (ii) inserting a sub-query node between the nodes of one or more of said common-referencing pairs of nodes, or by separately performing both (i) and (ii) on respective ones of said common-referencing pairs of nodes to sequence the execution of each said common-referencing pair of nodes to produce a query graph G.sub.MTI that enforces database integrity during table mutation;
• means, recorded on said recording medium, for causing said system to generate a plurality of plans for executing said query graph G.sub.MTI ;
• and
• means, recorded on said recording medium, for causing said system to evaluate the execution cost of each said query execution plan and selecting said optimal query execution plan.