Database query processing

• US 10,459,913 B2
• Filed: 02/26/2015
• Issued: 10/29/2019
• Est. Priority Date: 02/26/2015
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Inventors: Nguyen, Filip, Elias, Filip
• Primary Examiner(s): Reyes, Mariela
• Assistant Examiner(s): Mincey, Jermaine A
• Application Number:
  US14/632,736
• Publication Number:
  US 20160253372A1
• Time in Patent Office: 1,706 Days
• Field of Search: None
• CPC Class Codes: G06F 16/2282 Tablespace storage structures; Management thereof
• CPC Class Codes: G06F 16/2379 Updates performed during online database operations; commit processing
• CPC Class Codes: G06F 16/245 Query processing

Abstract

Various examples are directed to systems and methods for managing a database organized according to a schema. The database may comprise a database file corresponding to a table described by the schema. The database file may comprise a first row entry corresponding to a first row of the table. The first row entry may comprise at least one data item. A command may be received. The command may modify a first data item in the first row of the table. An indication of the modified value for the first data item may be written to a change location at the first file. The first entry may be modified to include a pointer to the indication of the modified value for the first data item.

Claims

1. A system for managing a relational database organized according to a schema, the system comprising:

a computer-readable medium, the computer-readable medium comprising a first file, wherein the first file stores a relational database table described by the schema, the first file comprises a sequence of row entries, each row entry in the sequence of row entries corresponds to a row of the table, and each row entry in the sequence of row entries comprises a sequence of data items in the row corresponding to the row entry; and

at least one processor in communication with the computer-readable medium and programmed to;

receive a command to modify a value of a first data item of the relational database table, wherein the command indicates a modified value for the first data item;

responsive to receiving the command and without modifying the schema, write a first change entry to the first file prior to the sequence of row entries, wherein the first change entry comprises the modified value for the first data item, and an indicator of a column corresponding to the first data item;

identify from the sequence of row entries a first row entry comprising the first data item; and

without modifying the schema, write to the first row entry, at a position corresponding to the first data item, a pointer to the first change entry that associates the first change entry to the first row entry without updating the first row entry with the modified value for the first data item during a response to the command to modify.

2. The system of claim 1, wherein the at least one processor is further programmed to:

receive, from a client, a query for a plurality of data items comprising the first data item;

responsive to receiving the query, determine that the client has not previously received a result for the query;

load to a cache location and from the first file a set of row entries selected from the sequence of row entries, wherein the set of row entries corresponds to rows potentially relevant to the query, and wherein the set of row entries comprises the first row entry;

at the cache location, create a modified first row entry by replacing the pointer with the modified value for the first data item; and

return to the client a result of the query, wherein the result comprises the modified first row entry value.

3. The system of claim 1, wherein the at least one processor is further programmed to:

receive, from a client, a query for a plurality of data items comprising the first data item, wherein the plurality of data items include pointers to a plurality of change entries that include respective modified values associated with respective data items of the plurality of data items;

responsive to receiving the query, determine that the client has previously received a first result for the query in response to a previous iteration of the query, wherein the first result includes a first subset of the plurality of change entries;

identify, based on a sequence of the plurality of change entries, a second subset of the plurality of change entries that have been added to the first file since the first result was sent to the client; and

return to the client a second result of the query, wherein the second result comprises the second subset of change entries.

4. A system for managing a relational database organized according to a schema, the system comprising:

a computer-readable medium, the computer-readable medium comprising a first file storing a relational database table described by the schema, wherein the first file comprises a first row entry, the first row entry corresponds to a first row of the table, and the first row entry comprises at least one data item; and

at least one processor in communication with the computer-readable medium and programmed to;

receive a command to modify a value of a first data item in the first row of the table, wherein the command indicates a modified value for the first data item;

responsive to receiving the command and without modifying the schema, write an indication of the modified value for the first data item to a change location at the first file;

identify the first row entry from the first file; and

without modifying the schema, write to the first row entry a pointer to the indication of the modified value for the first data item that associates the modified value to the first row entry and the first data item without updating the first row entry with the modified value for the first data item during a response to the command to modify.

5. The system of claim 4, wherein the at least one processor is further programmed to write to the change location at the first file, in association with the modified value for the first data item, an indicator of a column corresponding to the first data item.

6. The system of claim 4, wherein the first file comprises a set of sequential row entries comprising the first row entry, and wherein the change location at the first file is prior to the set of sequential row entries.

7. The system of claim 4, wherein the first file comprises a set of sequential row entries comprising the first row entry, and wherein the change location at the first file is after the set of sequential row entries.

8. The system of claim 4, wherein the at least one processor is further programmed to:

receive, from a client, a query for the first data item;

responsive to receiving the query, determine that the client has not previously received a result for the query;

load a plurality of row entries, the plurality of row entries comprising the first row entry;

modify the loaded first row entry to replace the pointer with the modified value from the change location for the first data item; and

return to the client a result of the query, wherein the result comprises the modified value for the first data item.

9. The system of claim 8, wherein the at least one processor is further programmed to write to a query log an indication that the client received the result of the query.

10. The system of claim 9, wherein the at least one processor is further programmed to:

receive a command to modify a value of a second data item in the first row of the table, wherein the command indicates a modified value for the second data item;

responsive to receiving the command and without modifying the schema, write an indication of the modified value for the second data item to the change location at the first file; and

without modifying the schema, write to the first row entry, at a position corresponding to the second data item, a pointer to the indication of the modified value for the second data item.

11. The system of claim 10, wherein the at least one processor is further programmed to write to the query log an indication of the command to modify the value of the second data item.

12. The system of claim 4, wherein the at least one processor is further programmed to:

receive, from a client, a query to the relational database;

responsive to receiving the query, determine that the client has previously received a result of the query;

identify at least one data item value change to the relational database that has occurred since the client previously received the result of the query;

read from the change location at least one data item value corresponding to the at least one change; and

transmit the at least one data item value to the client.

13. The system of claim 4, wherein the at least one processor is further programmed to:

receive from a client a query for the first data item;

responsive to receiving the query, determine that the client has previously received a result of the query;

identify at least one modified value for a data item at the change location of the first file that has been added to the first file since the client previously received the result of the query, wherein the at least one modified value for the data item comprises the modified value for the first data item; and

return to the client a result of the query, wherein the result of the query comprises at least one change entry that includes the modified value for the first data item.

14. The system of claim 4, wherein the first file also comprises at least one row entry corresponding to a row of a second table described by the schema.

15. A system for managing a relational database organized according to a schema, the system comprising:

a computer-readable medium, the computer-readable medium comprising a first file storing a relational database table described by the schema, wherein the first file comprises;

a first change entry comprising a modified value for a first data item, wherein the first change entry is written to a change location of the first file without a modification to the schema; and

a first row entry, wherein the first row entry corresponds to a first row of the table, the first row entry lacks the modified value, and wherein the first row entry comprises at a position corresponding to the first data item, a pointer to the first change entry that associates the first change entry to the first row entry; and

at least one processor in communication with the computer-readable medium and programmed to;

receive from a client a query for the first data item;

responsive to receiving the query, determine that the client has not previously received a result for the query;

load from the first file a plurality of row entries, the plurality of row entries comprising the first row entry;

modify the loaded first row entry to replace the pointer with the modified value for the first data item; and

return to the client a result of the query, wherein the result of the query comprises the modified value for the first data item.

16. The system of claim 15, wherein the at least one processor is further programmed to:

receive from a second client a second query for the first data item;

responsive to receiving the second query, determine that the second client has previously received a result of the second query;

identify at the change location at least one change entry that has been added to the first file without modifying the schema since the second client previously received the result of the second query, the at least one change entry comprising the first change entry; and

return to the second client a second result of the second query, wherein the second result of the second query comprises the at least one change entry.

17. The system of claim 15, wherein the first file comprises a set of sequential row entries comprising the first row entry, and wherein the change location at the first file is prior to the set of sequential row entries.

18. The system of claim 15, wherein the first file comprises a set of sequential row entries comprising the first row entry, and wherein the change location at the first file is after the set of sequential row entries.

19. The system of claim 15, wherein the first change entry further comprises an indication of a column corresponding to the first data item.

20. The system of claim 15, wherein the first file also comprises a second row entry corresponding to a first row of a second table described by the schema.