OLTP COMPRESSION OF WIDE TABLES

• US 20140279959A1
• Filed: 03/12/2013
• Published: 09/18/2014
• Est. Priority Date: 03/12/2013
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Marwah, Vineet, Mylavarapu, Ajit, Ganesh, Amit
• Granted Patent: US 9,646,053 B2
• Time in Patent Office: Days
• US Class Current: 707/693
• CPC Class Codes: G06F 16/24556 Aggregation; Duplicate elimination

Abstract

A data block stores one or more rows of a database table or relation. An entire row may not fit in a data block. Part of the row is stored in one data block, and another part is stored in another data block. Each row part is referred to herein as a row segment and the data blocks are referred to as row-segmented data blocks. Data block dictionary compression is used to compress row-segmented data blocks. Each data block contains a dictionary that is used to compress rows in the data block, including row segments. The dictionary in a data block is used to compress row segments in the data block. Hence, multiple dictionaries may be used to decompress a row comprised of row segments.

Claims

1. A method comprising steps of:

a database server storing a plurality of rows in a plurality of data blocks, wherein storing said plurality of data blocks includes;

compressing said plurality of rows in said plurality of data blocks using token dictionary compression and a plurality of token dictionaries; and

wherein said plurality of rows includes segmented rows, each segmented row of said segmented rows comprising a plurality of chained row segments, each row segment of said plurality of chained row segments containing one or more column values of said each segmented row.

2. The method of claim 1, wherein each data block of said plurality of data blocks stores a respective token dictionary of said plurality of token dictionaries.

3. The method of claim 2, wherein the respective token dictionary of said each data block only maps tokens to column values stored in said each data block.

4. The method of claim 1, wherein:

each data block of said plurality of data blocks stores a respective token dictionary of said plurality of token dictionaries that only maps tokens to column values stored in said data blocks;

wherein said segmented rows includes a first row comprising a first row segment in a first data block of said plurality of data blocks and a second row segment in a second data block of said plurality of data blocks; and

wherein said first row segment is encoded according to the respective token dictionary stored in said first data block and wherein the second row segment is encoded according to the respective token dictionary of second data block.

5. The method of claim 4, the steps further including decoding said first row, wherein decoding said first row includes decoding said first row segment according to the respective token dictionary of said first data block and decoding said second row segment according to the respective token dictionary of said second data block.

6. The method of claim 1, wherein a first segmented row of said segmented rows comprises at least two row segments stored in a same data block of said plurality of data blocks.

7. The method of claim 1, where a first segmented row of said segmented rows comprises at least two row segments stored in different data blocks of said plurality of data blocks.

8. A method, comprising:

a database server inserting a row into a database table, wherein inserting a row into a database table comprises;

storing a first row segment of said row in a first data block, said storing a first row segment of said row in a first data block comprising;

compressing one or more column values contained in said first row segment according to a first token dictionary stored in said first data block; and

storing a second row segment of said row into a second data block, said storing comprising compressing one or more column values contained in said second row segment according to a second token dictionary stored in said second data block.

9. The method of claim 8, wherein compressing one or more column values contained in said first row segment includes adding an entry to said first token dictionary mapping one or more tokens to said one or more column values.

10. A non-transitory computer-readable medium storing one or more instructions which when executed by one or more processors cause the one or more processors to perform steps comprising:

a database server storing a plurality of rows in a plurality of data blocks, wherein storing said plurality of data blocks includes;

compressing said plurality of rows in said plurality of data blocks using token dictionary compression and a plurality of token dictionaries; and

wherein said plurality of rows includes segmented rows, each segmented row of said segmented rows comprising a plurality of chained row segments, each row segment of said plurality of chained row segments containing one or more column values of said each segmented row.

11. The non-transitory computer-readable medium of claim 10, wherein each data block of said plurality of data blocks stores a respective token dictionary of said plurality of token dictionaries.

12. The non-transitory computer-readable medium of claim 11, wherein the respective token dictionary of said each data block only maps tokens to column values stored in said each data block.

13. The non-transitory computer-readable medium of claim 10, wherein:

each data block of said plurality of data blocks stores a respective token dictionary of said plurality of token dictionaries that only maps tokens to column values stored in said data blocks;

wherein said segmented rows includes a first row comprising a first row segment in a first data block of said plurality of data blocks and a second row segment in a second data block of said plurality of data blocks; and

wherein said first row segment is encoded according to the respective token dictionary stored in said first data block and wherein the second row segment is encoded according to the respective token dictionary of second data block.

14. The non-transitory computer-readable medium of claim 13, the steps further including decoding said first row, wherein decoding said first row includes decoding said first row segment according to the respective token dictionary of said first data block and decoding said second row segment according to the respective token dictionary of said second data block.

15. The non-transitory computer-readable medium of claim 10, wherein a first segmented row of said segmented rows comprises at least two row segments stored in a same data block of said plurality of data blocks.

16. The non-transitory computer-readable medium of claim 10, where a first segmented row of said segmented rows comprises at least two row segments stored in different data blocks of said plurality of data blocks.

17. A non-transitory computer-readable medium storing one or more instructions which when executed by one or more processors cause the one or more processors to perform steps comprising:

a database server inserting a row into a database table, wherein inserting a row into a database table comprises;

storing a first row segment of said row in a first data block, said storing a first row segment of said row in a first data block comprising;

compressing one or more column values contained in said first row segment according to a first token dictionary stored in said first data block; and

storing a second row segment of said row into a second data block, said storing comprising compressing one or more column values contained in said second row segment according to a second token dictionary stored in said second data block.

18. The non-transitory computer-readable medium of claim 17, wherein compressing one or more column values contained in said first row segment includes adding an entry to said first token dictionary mapping one or more tokens to said one or more column values.