Refreshing materialized views of a database to maintain consistency with underlying data

A system, comprising:

• a database, containing data which changes over time;
• means for providing
• immediate views of the database, which are refreshed whenever changes occur to the database;
• deferred views of the database, which are refreshed whenever a query is made upon the deferred view;
• and
• snapshot views of the database, which are refreshed at intervals;
• means responsive to user input for collecting selected immediate views, deferred views, and snapshot views into respective view groups;
• and
• means for maintaining mutual consistency of all views within every view group.

A method of operating a system which contains a database, comprising the following steps:

• maintaining views, at least one of which are views of other views, and at least one of which of which are views of the database;
• maintaining a view dependency graph of dependency relations of the views;
• and
• in predetermined groups of views, maintaining mutual consistency in the data within each view group.

A system, comprising:

• a database;
• means for generating views based on the database, in which at least one view depends on at least one other view;
• and
• means for maintaining data which represents dependency relationships of the views,
• wherein all views exhibit the following characteristics:
• a) each view is assigned to exactly one view group;
• b) all immediate views and deferred views belong to the same viewgroup as their parents;
• c) if any snapshot view in a viewgroup VG is updated in a transaction T, then all snapshot views in VG are updated in T;
• d) no snapshot view occurs in the same view group as base tables;
• e) every view group is derived from at most one other viewgroup;
• f) deferred views have no children in any other viewgroups;
• g) no immediate view has a deferred view or a snapshot view as a parent;
• h) no snapshot view has a deferred view as a parent;
• and
• i) all the base tables are included in a single view group (VGBase).

A system, comprising:

• a database;
• means for generating views based on the database, in which at least one view depends on at least one other view;
• and means for maintaining data which represents dependency relationships of the views,
• wherein each view is assigned to exactly one view group, and all views exhibit at least one of the following characteristics:
• a) all immediate views and deferred views belong to the same viewgroup as their parents;
• b) if any snapshot view in a viewgroup VG is updated in a transaction T, then all snapshot views in VG are updated in T;
• c) no snapshot view occurs in the same view group as base tables;
• d) every view group is derived from at most one other viewgroup;
• e) deferred views have no children in any other viewgroups;
• f) no immediate view has a deferred view or a snapshot view as a parent;
• and
• g) no snapshot view has a deferred view as a parent.

In a system containing:

• a database;
• means for generating views based on he database, in which at least one view depends on at least one other view;
• and
• means for maintaining data which represents dependency relationships of the views,
• the improvement comprising the following steps:
• a) eliminating snapshot views from view groups containing base tables;
• and
• b) if any snapshot view in a viewgroup VG is updated in a transaction T, then updating all snapshot views in VG.

In a system containing:

• a database;
• means for generating views based on the database, in which at least one view depends on at least one other view;
• means for generating views based on the database, in which some views depend on other views;
• and
• means for maintaining data which represents dependency relationships of the views,
• wherein each view is assigned to exactly one view group, the improvement comprising the following steps:
• a) keeping no snapshot views in view groups containing base tables;
• and
• b) if any snapshot view in a viewgroup VG is updated in a transaction T, then updating all snapshot views in VG.

A system, comprising:

• a database;
• means for generating views based on the database, in which at least one view depends on at least one other view;
• and
• means for maintaining data which represents dependency relationships of the views,
• wherein views exhibit the following characteristics:
• a) each view is assigned to exactly one view group;
• b) every view group is derived from at most one other viewgroup;
• and
• c) all base tables are included in a single view group (VGBase).

A system, comprising:

• a database;
• means for generating views based on the database, in which at least one view depends on at least one other view;
• means for generating views based on the database, in which some views depend on other views;
• and
• means for maintaining data which represents dependency relationships of the views,
• wherein each view is assigned to exactly one view group, the improvement comprising the following steps:
• a) each view is assigned to exactly one view group;
• b) every view group is derived from at most one other view group;
• and
• c) all base tables are included in a single view group (VGBase).

A system, comprising:

• a database;
• means for generating views based on the database, in which at least one view depends on at least one other view;
• and
• means for maintaining data which represents dependency relationships of the views,
• wherein respective views exhibit the following characteristics:
• a) all immediate views and deferred views belong to the same viewgroup as their parents;
• b) if any snapshot view in a viewgroup VG is updated in a transaction T, then all snapshot views in VG are updated in T;
• c) no snapshot view occurs in the same view group as base tables;
• d) deferred views have no children in any other viewgroups;
• e) no immediate view has a deferred view or a snapshot view as a parent;
• and
• f) no snapshot view has a deferred view as a parent.

A system, comprising:

• a database;
• means for generating views based on the database, in which at least one view depends on at least one other view;
• means for generating views based on the database, in which some views depend on other views;
• and
• means for maintaining data which represents dependency relationships of the views,
• wherein each view is assigned to exactly one view group, and respective views exhibit the following characteristics:
• a) if any snapshot view in a viewgroup;
• VG is updated in a transaction T, then all snapshot views in VG are updated in T;
• b) no snapshot view occurs in the same view group as base tables;
• c) deferred views have no children in any other viewgroups;
• d) no immediate view has a deferred view or a snapshot view as a parent;
• and
• e) no snapshot view has a deferred view as a parent.