Relational database page-level schema transformations
View Patent ↗Methods, devices and systems which facilitate the conversion of database objects from one schema version (e.g., an earlier version) to another schema version (e.g., a newer version) without requiring the objects be unloaded and reloaded are described. In general, data object conversion applies to both table space objects and index space objects. The described transformation techniques may be used to convert any object whose schema changes occur at the page-level.
1. A general purpose computer programmed to perform a database schema transformation method, the method comprising:
identifying a first database object, the first database object having a plurality of pages and a first schema;
specifying a second version of the first database object and referred to as a second database object, the second database object having a schema with at least one page-level attribute that is different from the first schema and referred to as a second schema;
determining, for each page in the first database object, how each page-level attribute that is different between the first schema and the second schema will cause said page to change page-position when transformed from the first database object to the second database object;
generating an entry in a transformation table for every one or more contiguous first database object pages determined to have a common page-position offset, wherein every page in the first database object is associated with a single entry in the transformation table; and
transforming each page in the first database object into the second database.
2. The method of claim 1 wherein the act of identifying a first database object comprises:
identifying a source database object; and
copying the source database object to make the first database object.
3. The method of claim 2 , wherein the act of copying comprises making a consistent copy of the source database object to make the first database object.
4. The method of claim 1 , wherein the act of specifying a second version of the first database object having a schema with at least one page-level attribute that is different from the first schema comprises specifying one or more of the following page-level attributes: page size and row identifier size.
5. The method of claim 4 , wherein the act of identifying a first database object comprises identifying a table space database object and the act of specifying a second version of the first database object having a schema with at least one page-level attribute that is different from the first schema comprises specifying one or more of the following page-level attributes: data set size and segment size.
6. The method of claim 4 , wherein the act of identifying a first database object comprises identifying an index space database object and the act of specifying a second version of the first database object having a schema with at least one page-level attribute that is different from the first schema comprises specifying one or more of the following page-level attributes: piece size and compression attribute.
7. The method of claim 1 , wherein the first database object comprises a nonpartitioned database object and the second database object comprises a partitioned database object.
8. The method of claim 1 wherein the act of generating an entry in a transformation table comprises:
generating a low-page-number portion for each transformation table entry, the low-page-number portion being a value representing a first page number in the first database object;
generating a high-page-number portion for each transformation table entry, the high-page-number portion being a value representing a second page number in the first database object; and
generating an offset portion for each transformation table entry, the offset portion being a value.
9. The method of claim 8 , further comprising storing the transformation, table entry in a memory.
10. The method of claim 9 , wherein the act of storing the transformation table entry in a memory comprises storing the transformation table entry in a volatile memory.
11. The method of claim 8 wherein the act of transforming each page in the first database object into the second database object comprises:
obtaining a page from the first database object, the page having a page number;
selecting that transformation table entry whose low-page-number portion and high-page-number portion bounds the page number;
updating the page number by adding the offset portion value to the page number; and
inserting the page into the second database object at a location indicated by the updated page number.
12. The method of claim 11 wherein the act of transforming each page in the first database object into the second database object further comprises updating one or more of the following aspects of the page: row identifier and partition identifier.
13. The method of claim 11 wherein the act of transforming each page in the first database object into the second database object further comprises inserting one or more of the following into the second database object: a spacemap, a compression dictionary and a system page.
14. An article of manufacture comprising a program storage medium readable by a computer processor and embodying one or more instructions executable by the computer processor to perform a method in accordance with claim 1 .
15. A computer network executing a method to transform a relational database object, the computer network comprising:
a storage device for the non-volatile storage of a relational database object;
a computer system communicatively coupled to the network and the storage device, the computer system having memory, the memory having stored therein program instructions for causing the computer system to perform the method of claim 1 .