Partitioning in Oracle 9i Since partitioning is such an integral part of VLDB the remainder of this article will focus on how to partition, specifically, the partitioning of tables in an Oracle 9i. The complete article will cover: When To Partition Different Methods Of Partitioning Partitioning Of Tables Partitioning Of Indexes When to use each case Managing Partitions When To Partition There are two main reasons to use partitioning in a VLDB environment. These reasons are related to management and performance improvement. Partitioning offers: - Management at the individual partition level for data loads, index creation and rebuilding, and backup/recovery. This can result in less down time because only individual partitions being actively managed are unavailable. - Increased query performance by selecting only from the relevant partitions. This weeding out process eliminates the partitions that do not contain the data needed by the query through a technique called partition pruning. The decision about exactly when to use partitioning is rather subjective. Some general guidelines that Oracle suggest are listed below. Use partitioning: - When a table reaches a "large" size. Large being defined relative to your environment. Tables greater than 2GB should
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Partitioning in Oracle 9iSince partitioning is such an integral part of VLDB the remainder of this article will focus on how to partition, specifically, the partitioning of tables in an Oracle 9i. The complete article will cover:
When To Partition Different Methods Of Partitioning Partitioning Of Tables Partitioning Of Indexes When to use each case Managing Partitions
When To PartitionThere are two main reasons to use partitioning in a VLDB environment. These reasons are related to management and performance improvement.
Partitioning offers:- Management at the individual partition level for data loads, index creation and rebuilding, and backup/recovery. This can result in less down time because only individual partitions being actively managed are unavailable.- Increased query performance by selecting only from the relevant partitions. This weeding out process eliminates the partitions that do not contain the data needed by the query through a technique called partition pruning.
The decision about exactly when to use partitioning is rather subjective. Some general guidelines that Oracle suggest are listed below.Use partitioning:- When a table reaches a "large" size. Large being defined relative to your environment. Tables greater than 2GB should always be considered for partitioning.- When performance benefits outweigh the additional management issues related to partitioning.- When the archiving of data is on a schedule and is repetitive. For instance, data warehouses usually hold data for a specific amount of time (rolling window). Old data is then rolled off to be archived.
Take a moment and evaluate the criteria above to make sure that partitioning is advantageous for your environment. In larger environments partitioning is worth the time to investigate and implement.
Different Methods of PartitioningOracle 9i, Release 2 has five partitioning methods for tables. They are listed in the table below with a brief description
Range Partitioning Used when there are logical ranges of data. Possible usage: dates, part numbers, and serial numbers
Hash Partitioning Used to spread data evenly over partitions. Possible usage: data has no logical groupings
List Partitioning Used to list together unrelated data into partitions. Possible usage: a number of states list partitioned into a region
Composite Range-Hash Partitioning
Used to range partition first, then spreads data into hash partitions. Possible usage: range partition by date of birth then hash partition by name; store the results into the hash partitions
Composite Range-List Partitioning
Used to range partition first, then spreads data into list partitions.Possible usage: range partition by date of birth then list partition by state, then store the results into the list partitions
For partitioning of indexes, there are global and local indexes. Global indexes provide greater flexibility by allowing indexes to be independent of the partition method used on the table. This allows for the global index to reference different partitions of a single table. Local indexes (while less flexible than global) are easier to manage. Local indexes are mapped to a specific partition. This one-to-one relationship between local index partitions and table partitions allows Oracle the ability to manage local indexes.The use of the ENABLE ROW MOVEMENT clause is included in all of the examples of table partitioning to allow row movement if the partition key is updated.
Partitioning Of Tables
Range PartitioningRange partitioning was the first partitioning method supported by Oracle in Oracle 8. For example, business transactions can be partitioned by various versions of date (start date, transaction date, close date, or date of payment). Range partitioning can also be performed on part numbers, serial numbers or any other ranges that can be discovered. The example provided for range partition will be on a table named PARTITION_BY_RANGE, the actual partitioning is on the following columns BIRTH_YYYY, BIRTH_MM, and BIRTH_DD. Each partition is assigned to its own tablespace. The last partition is the "catch all" partition. By using MAXVALUE the last partition will contain all the records with values over the second to last partition
-- RANGE_ME.SQL-- PARTITION BY RANGE ON BIRTH DATESCREATE TABLE PARTITION_BY_RANGE( FIRST_NAME VARCHAR2(10), MIDDLE_INIT VARCHAR2(1), LAST_NAME VARCHAR2(10), BIRTH_MM INT NOT NULL, BIRTH_DD INT NOT NULL, BIRTH_YYYY INT NOT NULL)PARTITION BY RANGE (BIRTH_YYYY, BIRTH_MM, BIRTH_DD)(PARTITION DOBS_IN_1971_OR_BEFORE VALUES LESS THAN (1972, 01 ,01) TABLESPACE TS01, PARTITION DOBS_IN_1972 VALUES LESS THAN (1973, 01 ,01) TABLESPACE TS02, PARTITION DOBS_IN_1973 VALUES LESS THAN (1974, 01 ,01) TABLESPACE TS03, PARTITION DOBS_IN_1974 VALUES LESS THAN (1975, 01 ,01) TABLESPACE TS04, PARTITION DOBS_IN_1975_OR_LATER VALUES LESS THAN (MAXVALUE, MAXVALUE, MAXVALUE) TABLESPACE TS05)ENABLE ROW MOVEMENT;
-- CHECK TO SEE IF THE PARTITIONS ARE CORRECTLY BUILTSELECT TABLE_NAME, PARTITION_NAME, HIGH_VALUE, TABLESPACE_NAMEFROM USER_TAB_PARTITIONSWHERE TABLE_NAME = 'PARTITION_BY_RANGE'ORDER BY TABLESPACE_NAME;
-- Insert Data Into Each PartitionINSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1969', 'A', 'SMITH_1969', 09, 20, 1969);INSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1970', 'A', 'SMITH_1970', 09, 20, 1970);INSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1971', 'A', 'SMITH_1971', 09, 20, 1971);INSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1972', 'A', 'SMITH_1972', 09, 20, 1972);INSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1973', 'A', 'SMITH_1973', 09, 20, 1973);INSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1974', 'A', 'SMITH_1974', 09, 20, 1974);INSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1975', 'A', 'SMITH_1975', 09, 20, 1975);INSERT INTO PARTITION_BY_RANGE VALUES ('FRED_1976', 'A', 'SMITH_1976', 09, 20, 1976);COMMIT;
-- Confirmation that everything is in the proper placeSELECT * FROM PARTITION_BY_RANGE;SELECT * FROM PARTITION_BY_RANGE PARTITION (DOBS_IN_1971_OR_BEFORE);SELECT * FROM PARTITION_BY_RANGE PARTITION (DOBS_IN_1972);SELECT * FROM PARTITION_BY_RANGE PARTITION (DOBS_IN_1973);SELECT * FROM PARTITION_BY_RANGE PARTITION (DOBS_IN_1974);SELECT * FROM PARTITION_BY_RANGE PARTITION (DOBS_IN_1975_OR_LATER);
Hash PartitioningOracle's hash partitioning distributes data by applying a proprietary hashing algorithm to the partition key and then assigning the data to the appropriate partition. By using hash partitioning, DBA's can partition data that may not have any logical ranges. Also, DBA's do not have to know anything about the actual data itself. Oracle handles all of the distribution of data once the partition key is identified.Please note that the data may not appear to be distributed evenly because of the limited number of inserts applied to the tableA brief explanation of the code follows. The PARTITION BY HASH line is where the partition key is identified. In this example the partition key is AGE. Once the hashing algorithm is applied each record is distributed to a partition. Each partition is specifically assigned to its own tablespace
-- HASH_ME.SQL-- PARTITION BY HASH ON AGECREATE TABLE PARTITION_BY_HASH(FIRST_NAME VARCHAR2(10), MIDDLE_INIT VARCHAR2(1), LAST_NAME VARCHAR2(10), AGE INT NOT NULL)PARTITION BY HASH (AGE)(PARTITION P1_AGE TABLESPACE TS01, PARTITION P2_AGE TABLESPACE TS02, PARTITION P3_AGE TABLESPACE TS03, PARTITION P4_AGE TABLESPACE TS04)ENABLE ROW MOVEMENT;
-- CHECK TO SEE IF THE PARTITIONS ARE CORRECTLY BUILTSELECT TABLE_NAME, PARTITION_NAME, TABLESPACE_NAMEFROM USER_TAB_PARTITIONSWHERE TABLE_NAME = 'PARTITION_BY_HASH'ORDER BY TABLESPACE_NAME;
-- Insert Data Into Each PartitionINSERT INTO PARTITION_BY_HASH VALUES ('MIKE', 'F', 'SMITH', 45);INSERT INTO PARTITION_BY_HASH VALUES ('JANE', 'R', 'SMITH', 50);INSERT INTO PARTITION_BY_HASH VALUES ('NICK', 'R', 'SMITH', 55);INSERT INTO PARTITION_BY_HASH VALUES ('KIMM', 'B', 'SMITH', 60);INSERT INTO PARTITION_BY_HASH VALUES ('FRED', 'A', 'SMITH', 70);INSERT INTO PARTITION_BY_HASH VALUES ('BILL', 'B', 'SMITH', 80);INSERT INTO PARTITION_BY_HASH VALUES ('JOHN', 'C', 'SMITH', 90);INSERT INTO PARTITION_BY_HASH VALUES ('DAVE', 'D', 'SMITH', 100);COMMIT;
-- Confirmation that data is being spread between the partitionsSELECT * FROM PARTITION_BY_HASH ORDER BY AGE;SELECT * FROM PARTITION_BY_HASH PARTITION (P1_AGE);SELECT * FROM PARTITION_BY_HASH PARTITION (P2_AGE);SELECT * FROM PARTITION_BY_HASH PARTITION (P3_AGE);SELECT * FROM PARTITION_BY_HASH PARTITION (P4_AGE);
List PartitioningList partitioning was added as a partitioning method in Oracle 9i, Release 1. List partitioning allows for partitions to reflect real-world groupings (e.g.. business units and territory regions). List partitioning differs from range partition in that the groupings in list partitioning are not side-by-side or in a logical range. List partitioning gives the DBA the ability to group together seemingly unrelated data into a specific partition. The LIST_ME.SQL script provides an example of a list partition table. Note the last partition with the DEFAULT value. This DEFAULT value is new in Oracle 9i, Release 2.A brief explanation of the code follows. The PARTITION BY LIST line is where the partition key is identified. In this example, the partition key is STATE. Each partition is explicitly named, contains a specific grouping of VALUES and is contained in its own tablespace. The last partition with the DEFAULT is the "catch all" partition. This catch all partition should be queried periodically to make sure that proper data is being entered.
-- CHECK TO SEE PARTITIONS ARE CORRECTLY BUILTSELECT TABLE_NAME, PARTITION_NAME, HIGH_VALUE, TABLESPACE_NAMEFROM USER_TAB_PARTITIONSWHERE TABLE_NAME = 'PARTITION_BY_LIST'ORDER BY TABLESPACE_NAME;
-- Insert Data Into Each PartitionINSERT INTO PARTITION_BY_LIST (DEPTID, DEPTNAME, STATE) VALUES (1,'ANCHORAGE' , 'AK');INSERT INTO PARTITION_BY_LIST (DEPTID, DEPTNAME, STATE) VALUES (2,'NEW YORK' , 'NY');INSERT INTO PARTITION_BY_LIST (DEPTID, DEPTNAME, STATE) VALUES (3,'DALLAS' , 'TX');INSERT INTO PARTITION_BY_LIST (DEPTID, DEPTNAME, STATE) VALUES (4,'LOS ANGELES', 'CA');INSERT INTO PARTITION_BY_LIST (DEPTID, DEPTNAME, STATE) VALUES (5,'WAIKIKI' , 'HI');COMMIT;
-- Confirmation that data is in the proper partitionsselect * from PARTITION_BY_LIST;select * from PARTITION_BY_LIST partition (depts_in_north);select * from PARTITION_BY_LIST partition (depts_in_east);select * from PARTITION_BY_LIST partition (depts_in_south);select * from PARTITION_BY_LIST partition (depts_in_west);select * from PARTITION_BY_LIST partition (depts_with_no_region);
Composite Range-Hash PartitioningComposite range-hash partitioning combines both the ease of range partitioning and the benefits of hashing for data placement, striping, and parallelism. Range-hash partitioning is slightly harder to implement. But, with the example provided and a detailed explanation of the code one can easily learn how to use this powerful partitioning method.I suggest that, when you actually try to build a range-hash partition table, you do it in the following steps:1. Determine the partition key for the range.2. Design a range partition table.3. Determine the partition key for the hash.4. Create the SUBPARTITION BY HASH clause.5. Create the SUBPARTITION TEMPLATE.Do Steps 1 and 2 first. Then you can insert the code created in Steps 3 -5 in the range partition table syntax.
The RANGE_HASH_ME.SQL script provides an example of a composite range-hash partition table. A brief explanation of the code follows. The PARTITION BY RANGE clause is where we shall begin. The partition key is (BIRTH_YYYY, BIRTH_MM, BIRTH_DD) for the partition. Next, the SUBPARTITION BY HASH clause indicates what the partition key is for the subpartition (in this case FIRST_NAME, MIDDLE_INIT, LAST_NAME). A SUBPARTITION TEMPLATE then defines the subpartition names and their respective tablespace. Subpartitions are automatically named by Oracle by concatenating the partition name, an underscore, and the subpartition name from the template. Remember that the total length of the subpartition name should not be longer than thirty characters including the underscore.
-- RANGE_HASH_ME.SQL-- PARTITION BY RANGE HASHCREATE TABLE PARTITION_BY_RANGE_HASH( FIRST_NAME VARCHAR2(10), MIDDLE_INIT VARCHAR2(1), LAST_NAME VARCHAR2(10), BIRTH_MM INT NOT NULL, BIRTH_DD INT NOT NULL, BIRTH_YYYY INT NOT NULL)TABLESPACE USERSPARTITION BY RANGE (BIRTH_YYYY, BIRTH_MM, BIRTH_DD) SUBPARTITION BY HASH(FIRST_NAME, MIDDLE_INIT, LAST_NAME) SUBPARTITION TEMPLATE( SUBPARTITION SP1 TABLESPACE TS01, SUBPARTITION SP2 TABLESPACE TS02,
SUBPARTITION SP3 TABLESPACE TS03, SUBPARTITION SP4 TABLESPACE TS04, SUBPARTITION SP5 TABLESPACE TS05)(PARTITION DOBS_IN_1971_OR_BEFORE VALUES LESS THAN (1972, 01 ,01), PARTITION DOBS_IN_1972 VALUES LESS THAN (1973, 01 ,01), PARTITION DOBS_IN_1973 VALUES LESS THAN (1974, 01 ,01), PARTITION DOBS_IN_1974 VALUES LESS THAN (1975, 01 ,01), PARTITION DOBS_IN_1975_OR_LATER VALUES LESS THAN (MAXVALUE, MAXVALUE, MAXVALUE))ENABLE ROW MOVEMENT;
-- CHECK TO SEE IF THE PARTITIONS ARE CORRECTLY BUILT AN IN THE PROPER TABLESPACESELECT TABLE_NAME, PARTITION_NAME, SUBPARTITION_NAME, TABLESPACE_NAMEFROM USER_TAB_SUBPARTITIONSWHERE TABLE_NAME = 'PARTITION_BY_RANGE_HASH';
-- INSERT DATA INTO EACH PARTITION-- DATA FOR PARTITION DOBS_IN_1971_OR_BEFOREINSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1966', 'A', 'SMITH_1966', 09, 20, 1966);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1967', 'A', 'SMITH_1967', 09, 20, 1967);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1968', 'A', 'SMITH_1968', 09, 20, 1968);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1969', 'A', 'SMITH_1969', 09, 20, 1969);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1970', 'A', 'SMITH_1970', 09, 20, 1970);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1971', 'A', 'SMITH_1971', 05, 16, 1971);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1971', 'A', 'SMITH_1971', 06, 17, 1971);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1971', 'A', 'SMITH_1971', 07, 18, 1971);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1971', 'A', 'SMITH_1971', 08, 19, 1971);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('FRED_1971', 'A', 'SMITH_1971', 09, 20, 1971);
-- DATA FOR PARTITION DOBS_IN_1972INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('BILL_1972', 'B', 'SMITH_1972', 05, 16, 1972);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('BILL_1972', 'B', 'SMITH_1972', 06, 17, 1972);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('BILL_1972', 'B', 'SMITH_1972', 07, 18, 1972);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('BILL_1972', 'B', 'SMITH_1972', 08, 19, 1972);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('BILL_1972', 'B', 'SMITH_1972', 09, 20, 1972);
-- DATA FOR PARTITION DOBS_IN_1973
INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('JOHN_1973', 'C', 'SMITH_1973', 05, 16, 1973);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('JOHN_1973', 'C', 'SMITH_1973', 06, 17, 1973);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('JOHN_1973', 'C', 'SMITH_1973', 07, 18, 1973);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('JOHN_1973', 'C', 'SMITH_1973', 08, 19, 1973);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('JOHN_1973', 'C', 'SMITH_1973', 09, 20, 1973);
-- DATA FOR PARTITION DOBS_IN_1974INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1974', 'D', 'SMITH_1974', 05, 16, 1974);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1974', 'D', 'SMITH_1974', 06, 17, 1974);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1974', 'D', 'SMITH_1974', 07, 18, 1974);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1974', 'D', 'SMITH_1974', 08, 19, 1974);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1974', 'D', 'SMITH_1974', 09, 20, 1974);
-- DATA FOR PARTITION DOBS_IN_1975_OR_LATERINSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1975', 'D', 'SMITH_1975', 09, 20, 1975);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1976', 'D', 'SMITH_1976', 09, 20, 1976);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1976', 'D', 'SMITH_1976', 09, 20, 1977);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1976', 'D', 'SMITH_1976', 09, 20, 1978);INSERT INTO PARTITION_BY_RANGE_HASH VALUES ('DAVE_1976', 'D', 'SMITH_1976', 09, 20, 1979);COMMIT;
-- CONFIRMATION THAT DATA IS BEING SPREAD BETWEEN THE PARTITIONSSELECT * FROM PARTITION_BY_RANGE_HASH;SELECT * FROM PARTITION_BY_RANGE_HASH PARTITION (DOBS_IN_1971_OR_BEFORE) ORDER BY BIRTH_YYYY;SELECT * FROM PARTITION_BY_RANGE_HASH PARTITION (DOBS_IN_1972) ORDER BY BIRTH_YYYY;SELECT * FROM PARTITION_BY_RANGE_HASH PARTITION (DOBS_IN_1973) ORDER BY BIRTH_YYYY;SELECT * FROM PARTITION_BY_RANGE_HASH PARTITION (DOBS_IN_1974) ORDER BY BIRTH_YYYY;SELECT * FROM PARTITION_BY_RANGE_HASH PARTITION (DOBS_IN_1975_OR_LATER) ORDER BY BIRTH_YYYY;
Composite Range-List PartitioningComposite range-list partitioning combines both the ease of range partitioning and the benefits of list partitioning at the subpartition level. Like range-hash partitioning, range-list partitioning needs to be carefully designed. The time used to properly design a range-list partition table pays off during the actual creation of the table. The
RANGE_LIST_ME.SQL script provides an example of a composite range-list partition table. A brief explanation of the code follows. The PARTITION BY RANGE clause identifies the partition key (BIRTH_YYYY, BIRTH_MM, BIRTH_DD). A SUBPARTITION TEMPLATE then defines the subpartition names and their respective tablespace. Subpartitions are automatically named by Oracle by concatenating the partition name, an underscore, and the subpartition name from the template. Remember that the total length of the subpartition name should not be longer than thirty characters including the underscore.
When building a range-list partition table you may want to refer to the steps mentioned at the end of the Composite Range-List section. The only difference is in Step 4. Instead of "Create the SUBPARTITION BY HASH clause" it would read, "Create the SUBPARTITION BY LIST clause" for the range-list partition table.
-- RANGE_LIST_ME.SQL-- PARTITION BY RANGE LIST (RANGE ON BIRTH DATES LIST BY STATE)CREATE TABLE PARTITION_BY_RANGE_LIST( FIRST_NAME VARCHAR2(10), MIDDLE_INIT VARCHAR2(1), LAST_NAME VARCHAR2(10), BIRTH_MM INT NOT NULL, BIRTH_DD INT NOT NULL, BIRTH_YYYY INT NOT NULL, STATE VARCHAR2(2) NOT NULL)TABLESPACE USERSPARTITION BY RANGE (BIRTH_YYYY, BIRTH_MM, BIRTH_DD) SUBPARTITION BY LIST (STATE) SUBPARTITION TEMPLATE (SUBPARTITION IN_NORTH VALUES ('AK') TABLESPACE TS01, SUBPARTITION IN_EAST VALUES ('NY', 'NJ', 'VA', 'CT') TABLESPACE TS02, SUBPARTITION IN_SOUTH VALUES ('TX', 'MS', 'GA', 'KY') TABLESPACE TS03, SUBPARTITION IN_WEST VALUES ('CA', 'AZ', 'OR', 'NV') TABLESPACE TS04, SUBPARTITION NO_STATE VALUES (DEFAULT) TABLESPACE TS05) (PARTITION DOBS_IN_1971_OR_B4 VALUES LESS THAN (1972, 01 ,01), PARTITION DOBS_IN_1972 VALUES LESS THAN (1973, 01 ,01), PARTITION DOBS_IN_1973 VALUES LESS THAN (1974, 01 ,01), PARTITION DOBS_IN_1974 VALUES LESS THAN (1975, 01 ,01), PARTITION DOBS_IN_1975_TO_MAX VALUES LESS THAN (MAXVALUE, MAXVALUE, MAXVALUE))ENABLE ROW MOVEMENT;
-- CHECK TO SEE IF THE PARTITIONS ARE CORRECTLY BUILT AN IN THE PROPER TABLESPACESELECT TABLE_NAME, PARTITION_NAME, SUBPARTITION_NAME, TABLESPACE_NAME FROM USER_TAB_SUBPARTITIONSWHERE TABLE_NAME = 'PARTITION_BY_RANGE_LIST';
-- Insert Data Into Each Partition-- DATA FOR DOBS_IN_1971_OR_BEFOREINSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 01, 01, 1970, 'AK');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 02, 02, 1970, 'NY');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 03, 03, 1970, 'TX');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 04, 04, 1970, 'CA');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 05, 05, 1970, 'HI');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 01, 01, 1971, 'AK');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 02, 02, 1971, 'NY');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 03, 03, 1971, 'TX');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 04, 04, 1971, 'CA');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 05, 05, 1971, 'HI');
-- DATA FOR DOBS_IN_1972INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 01, 01, 1972, 'AK');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 02, 02, 1972, 'NY');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 03, 03, 1972, 'TX');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 04, 04, 1972, 'CA');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 05, 05, 1972, 'HI');
-- DATA FOR DOBS_IN_1973INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 01, 01, 1973, 'AK');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 02, 02, 1973, 'NY');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 03, 03, 1973, 'TX');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 04, 04, 1973, 'CA');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 05, 05, 1973, 'HI');
-- DATA FOR DOBS_IN_1974INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 01, 01, 1974, 'AK');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 02, 02, 1974, 'NY');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 03, 03, 1974, 'TX');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 04, 04, 1974, 'CA');
-- DATA FOR DOBS_IN_1975_OR_LATERINSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 01, 01, 1975, 'AK');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 02, 02, 1975, 'NY');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 03, 03, 1975, 'TX');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 04, 04, 1975, 'CA');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 05, 05, 1975, 'HI');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 01, 01, 1976, 'AK');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 02, 02, 1976, 'NY');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 03, 03, 1976, 'TX');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 04, 04, 1976, 'CA');INSERT INTO PARTITION_BY_RANGE_LIST VALUES ('FN', 'M', 'LN', 05, 05, 1976, 'HI');COMMIT;
-- Confirmation that data is being spread between the partitionsSELECT * FROM PARTITION_BY_RANGE_LIST ORDER BY STATE, BIRTH_YYYY;
SELECT * FROM PARTITION_BY_RANGE_LIST PARTITION (DOBS_IN_1971_OR_B4) ORDER BY BIRTH_YYYY; SELECT * FROM PARTITION_BY_RANGE_LIST PARTITION (DOBS_IN_1972);
SELECT * FROM PARTITION_BY_RANGE_LIST PARTITION (DOBS_IN_1973);
SELECT * FROM PARTITION_BY_RANGE_LIST PARTITION (DOBS_IN_1974);
SELECT * FROM PARTITION_BY_RANGE_LIST PARTITION (DOBS_IN_1975_TO_MAX) ORDER BY BIRTH_YYYY;
Partitioning Of Indexes
Globally Partitioned IndexesThere are two types of global indexes, non-partitioned and partitioned. Global non-partitioned indexes are those that are commonly used in OLTP databases. The syntax for a globally non-partitioned index is the exactly same syntax used for a "regular" index on a non-partitioned table. Example:-- GNPI_ME.SQL-- GLOBAL NONPARTITION INDEX ON PARTITION_BY_RANGE-- (SIMILAR TO REGULAR INDEX USED ON NONPARTITION TABLES) IN MOST OLTP ENVIRONMENTS
CREATE INDEX PARTITION_BY_RANGE_GNPI ON PARTITION_BY_RANGE (LAST_NAME) TABLESPACE ITS01;
The other type of global index is the one that is partitioned. Globally partitioned indexes at this time can only be ranged partitioned and has similar syntactical structure to that of a range-partitioned table. Note that a globally partitioned index can be applied to any type of partitioned table. Each partition of the globally partitioned index can and may refer to one or more partitions at the table level. Example:-- GPI_ME.SQL-- GLOBAL PARTITION INDEX ON PARTITION_BY_RANGECREATE INDEX PARTITION_BY_RANGE_GPI ON PARTITION_BY_RANGE (BIRTH_YYYY, BIRTH_MM, BIRTH_DD)GLOBAL PARTITION BY RANGE (BIRTH_YYYY, BIRTH_MM, BIRTH_DD)(PARTITION DOBS_IN_1971_OR_BEFORE_GPI VALUES LESS THAN (1972, 01 ,01) TABLESPACE ITS01, PARTITION DOBS_IN_1972_GPI VALUES LESS THAN (1973, 01 ,01) TABLESPACE ITS02, PARTITION DOBS_IN_1973_GPI VALUES LESS THAN (1974, 01 ,01) TABLESPACE ITS03, PARTITION DOBS_IN_1974_GPI VALUES LESS THAN (1975, 01 ,01) TABLESPACE ITS04, PARTITION DOBS_IN_1975_OR_LATER_GPI VALUES LESS THAN (MAXVALUE, MAXVALUE, MAXVALUE) TABLESPACE ITS05);
The maintenance on globally partitioned indexes is a little bit more involved compared to the maintenance on locally partitioned indexes. Global indexes need to be rebuilt when there is DDL activity on the underlying table. The reason why they must be rebuilt is that DDL activity often causes the global indexes to be usually marked as UNUSABLE. To correct this problem there are two options to choose from:- Use ALTER INDEX <index_name> REBUILD;- Or use UPDATE GLOBAL INDEX clause when using ALTER TABLE.
The syntax for the ALTER INDEX statement is relatively straightforward so we will only focus on the UPDATE GLOBAL INDEX clause of the ALTER TABLE statement. The UPDATE GLOBAL INDEX is between the partition specification and the parallel clause. The partition specification can be any of the following:- ADD PARTITION | SUBPARTITION (hash only)- COALESCE PARTITION | SUBPARTITION- DROP PARTITION- EXCHANGE PARTITION | SUBPARTITION- MERGE PARTITION- MOVE PARTITION | SUBPARTITION- SPLIT PARTITION- TUNCATE PARTITION | SUBPARTITION
For example:ALTER TABLE <TABLE_NAME><PARTITION SPECIFICATION>UPDATE GLOBAL INDEX
PARALLEL (DEGREE #)
Locally Partitioned IndexesLocally partitioned indexes are for the most part very straightforward. The following script shows examples of this type of index. In the script, locally partitioned indexes are created on three differently partitioned tables (range, hash, and list).-- LPI_ME.SQLCREATE INDEX PARTITION_BY_RANGE_LI ON PARTITION_BY_RANGE (LAST_NAME) LOCAL(PARTITION RANGE_LIP_10 TABLESPACE ITS01, PARTITION RANGE_LIP_20 TABLESPACE ITS02, PARTITION RANGE_LIP_30 TABLESPACE ITS03, PARTITION RANGE_LIP_40 TABLESPACE ITS04, PARTITION RANGE_LIP_50 TABLESPACE ITS05);
Extra time should be allocated when creating locally partitioned indexes on range-hash or range-list partitioned tables. There are a couple reasons that extra time is needed for this type of index. One of the reasons is a decision needs to be made on what the index will be referencing in regards to a range-hash or range-list partitioned tables. A locally partitioned index can be created to point to either partition level or subpartition level.
The following script is the example for the creation of two locally partitioned indexes. This scripts show how to create a locally partitioned index on both a range-hash and range-list partitioned tables at the partition level. Each of the partitions of the locally partitioned indexes is assigned to its own tablespace for improved performance-- LPI4CPT1_ME.SQL INDEXES REFERCING THE PARTITION LEVEL-- USE EITHER LOCAL PARTITIONED INDEX ON THE PARTITION LEVEL OR SUBPARTITION LEVEL-- BUT NOT BOTH ON THE SAME INDEX COLUMN-- FOR COMPOSITE RANGE_HASH LOCAL PARTITIONED INDEX ON THE PARTITION LEVELCREATE INDEX PARTITION_BY_RANGE_HASH_LIP ON PARTITION_BY_RANGE_HASH (LAST_NAME) LOCAL(PARTITION RANGE_HASH_LIP_10 TABLESPACE ITS01, PARTITION RANGE_HASH_LIP_20 TABLESPACE ITS02, PARTITION RANGE_HASH_LIP_30 TABLESPACE ITS03, PARTITION RANGE_HASH_LIP_40 TABLESPACE ITS03, PARTITION RANGE_HASH_LIP_50 TABLESPACE ITS04);
-- USE EITHER LOCAL PARTITIONED INDEX ON THE PARTITION LEVEL OR SUBPARTITION LEVEL-- BUT NOT BOTH ON THE SAME INDEX COLUMN-- FOR COMPOSITE RANGE_LIST LOCAL PARTITIONED INDEX ON THE PARTITION LEVELCREATE INDEX PARTITION_BY_RANGE_LIST_LIP ON PARTITION_BY_RANGE_LIST (LAST_NAME) LOCAL(PARTITION RANGE_LIST_LIP_01 TABLESPACE ITS01, PARTITION RANGE_LIST_LIP_02 TABLESPACE ITS02, PARTITION RANGE_LIST_LIP_03 TABLESPACE ITS03, PARTITION RANGE_LIST_LIP_04 TABLESPACE ITS04, PARTITION RANGE_LIST_LIP_05 TABLESPACE ITS05);
When creating a locally partitioned index one needs to keep in mind the number of subpartitions of the range-hash or range-list partitioned table being indexed. Reason being, is that the locally partitioned index will need to reference each subpartition of the range-hash or range-list partitioned table. So, for the locally partitioned index created by LPI4CPT2_ME.SQL, this mean that one index references twenty-five different subpartitions. For a visual representation of this refer to Figure 4. Script LPI4CPT3_ME.SQL is provided as an example of locally partitioned index on a range-list partition table.
-- LOCAL COMPOSITE INDEXES REFERCING THE SUBPARTITION LEVEL-- LPI4CPT2_ME.SQL -- USE EITHER LOCAL PARTITIONED INDEX ON THE PARTITION LEVEL OR SUBPARTITION LEVEL-- BUT NOT BOTH ON THE SAME INDEX COLUMN-- FOR COMPOSITE RANGE_HASH LOCAL PARTITIONED INDEX ON THE SUBPARTITION LEVELCREATE INDEX PARTITION_BY_RANGE_HASH_LISP ON PARTITION_BY_RANGE_HASH (LAST_NAME) LOCAL(PARTITION RANGE_HASH_LISP_10 TABLESPACE ITS05 (SUBPARTITION RANGE_HASH_LISP_10_SP10 TABLESPACE ITS01 , SUBPARTITION RANGE_HASH_LISP_10_SP20 TABLESPACE ITS02 , SUBPARTITION RANGE_HASH_LISP_10_SP30 TABLESPACE ITS03 , SUBPARTITION RANGE_HASH_LISP_10_SP40 TABLESPACE ITS04 , SUBPARTITION RANGE_HASH_LISP_10_SP50 TABLESPACE ITS05 ), PARTITION RANGE_HASH_LISP_20 TABLESPACE ITS04 (SUBPARTITION RANGE_HASH_LISP_20_SP10 TABLESPACE ITS01 , SUBPARTITION RANGE_HASH_LISP_20_SP20 TABLESPACE ITS02 , SUBPARTITION RANGE_HASH_LISP_20_SP30 TABLESPACE ITS03 , SUBPARTITION RANGE_HASH_LISP_20_SP40 TABLESPACE ITS04 , SUBPARTITION RANGE_HASH_LISP_20_SP50 TABLESPACE ITS05 ), PARTITION RANGE_HASH_LISP_30 TABLESPACE ITS03 (SUBPARTITION RANGE_HASH_LISP_30_SP10 TABLESPACE ITS01 , SUBPARTITION RANGE_HASH_LISP_30_SP20 TABLESPACE ITS02 , SUBPARTITION RANGE_HASH_LISP_30_SP30 TABLESPACE ITS03 , SUBPARTITION RANGE_HASH_LISP_30_SP40 TABLESPACE ITS04 , SUBPARTITION RANGE_HASH_LISP_30_SP50 TABLESPACE ITS05 ), PARTITION RANGE_HASH_LISP_40 TABLESPACE ITS02
Note: At this time Oracle has not implemented a SUBPARTITION TEMPLATE clause for the creation of locally partitioned indexes on range-hash or range-list partition tables. This means that you need to type everything out as in the examples in LPI4CPT2_ME.SQL and LPI4CPT3_ME.SQL.Maintenance of locally partitioned indexes is much easier than the maintenance of globally partitioned indexes. Whenever there is DDL activity on the underlying indexed table Oracle rebuilds the locally partitioned index.This automatic rebuilding of locally partitioned indexes is one reason why most DBAs prefer locally partitioned indexes.
When to Use Which Partitioning MethodThere are five different table partitioning methods (range, hash, list, range-hash and range-list) and three for indexes (global non-partitioned, global partitioned and locally partitioned). So, the obvious question is: "When do I use which combination of table and index partitioning?" There is no concrete answer for that question. However, here are some general guidelines on mixing and matching table and index partitioning.- First determine if you need to partition the table.- Next decide which table partitioning method is right for your situation.- Determine how volatile the data is. o How often are there inserts, updates and deletes?- Choose your indexing strategy: global or local partitioned indexes. o Each type has its own maintenance consideration.
In identifying tables which would benefit from partitioning, consider the following: - Choose very large tables which grow rapidly, become fragmented quickly, and present maintenance challenges which could be alleviated by separate partition maintenance - Tables which have new data loaded regularly but are static thereafter - Summary tables, historical tables used in Decision Support Systems - Tables with data which has a logical partition column (date, code, type, etc)
When to Use the Range Partitioning MethodUse range partitioning to map rows to partitions based on ranges of column values. This type of partitioning is useful when dealing with data that has logical ranges into which it can be distributed; for example, months of the year. Performance is best when the data evenly distributes across the range. If partitioning by range causes partitions to vary dramatically in size because of unequal distribution, you may want to consider one of the other methods of partitioning.When creating range partitions, you must specify:
Partitioning method: range Partitioning column(s) Partition descriptions identifying partition bounds
When to Use the Hash Partitioning Method Use hash partitioning if your data does not easily lend itself to range partitioning, but you
would like to partition for performance and manageability reasons. Hash partitioning provides a method of evenly distributing data across a specified number of partitions. Rows are mapped into partitions based on a hash value of the partitioning key. Creating and using hash partitions gives you a highly tunable method of data placement, because you can influence availability and performance by spreading these evenly sized partitions across I/O devices (striping).
To create hash partitions you specify the following:
Partitioning method: hash Partitioning columns(s) Number of partitions or individual partition descriptions
The following example creates a hash-partitioned table. The partitioning column is id, four partitions are created and assigned system generated names, and they are placed in four named tablespaces (gear1, gear2, ...).
CREATE TABLE scubagear (id NUMBER, name VARCHAR2 (60)) PARTITION BY HASH (id) PARTITIONS 4 STORE IN (gear1, gear2, gear3, gear4);
When to Use the List Partitioning Methodse list partitioning when you require explicit control over how rows map to partitions. You can specify a list of discrete values for the partitioning column in the description for each partition. This is different from range partitioning, where a range of values is associated with a partition, and from hash partitioning, where the user has no control of the row to partition mapping. The list partitioning method is specifically designed for modeling data distributions that follow discrete values. This cannot be easily done by range or hash partitioning because:
Range partitioning assumes a natural range of values for the partitioning column. It is not possible to group together out-of-range values partitions.
Hash partitioning allows no control over the distribution of data because the data is distributed over the various partitions using the system hash function. Again, this makes it impossible to logically group together discrete values for the partitioning columns into partitions.
Further, list partitioning allows unordered and unrelated sets of data to be grouped and organized together very naturally.
Unlike the range and hash partitioning methods, multi-column partitioning is not supported for list partitioning. If a table is partitioned by list, the partitioning key can consist only of a single column of the table. Otherwise all columns that can be partitioned
by the range or hash methods can be partitioned by the list partitioning method. When creating list partitions, you must specify:
Partitioning method: list Partitioning column Partition descriptions, each specifying a list of literal values (a value list), which
are the discrete values of the partitioning column that qualify a row to be included in the partition
When to Use the Composite Range-Hash Partitioning MethodRange-hash partitioning partitions data using the range method, and within each partition, subpartitions it using the hash method. These composite partitions are ideal for both historical data and striping, and provide improved manageability of range partitioning and data placement, as well as the parallelism advantages of hash partitioning.
When creating range-hash partitions, you specify the following: Partitioning method: range Partitioning column(s) Partition descriptions identifying partition bounds Subpartitioning method: hash Subpartitioning column(s) Number of subpartitions for each partition or descriptions of subpartitions
The following statement creates a range-hash partitioned table. In this example, three range partitions are created, each containing eight subpartitions. Because the subpartitions are not named, system generated names are assigned, but the STORE IN clause distributes them across the 4 specified tablespaces (ts1, ...,ts4).
CREATE TABLE scubagear (equipno NUMBER, equipname VARCHAR(32), price NUMBER) PARTITION BY RANGE (equipno) SUBPARTITION BY HASH(equipname) SUBPARTITIONS 8 STORE IN (ts1, ts2, ts3, ts4) (PARTITION p1 VALUES LESS THAN (1000), PARTITION p2 VALUES LESS THAN (2000), PARTITION p3 VALUES LESS THAN (MAXVALUE));
The partitions of a range-hash partitioned table are logical structures only, as their data is stored in the segments of their subpartitions. As with partitions, these subpartitions share the same logical attributes. Unlike range partitions in a range-partitioned table, the subpartitions cannot have different physical attributes from the owning partition, although they are not required to reside in the same tablespace.
When to Use the Composite Range-List Partitioning MethodLike the composite range-hash partitioning method, the composite range-list partitioning method provides for partitioning based on a two level hierarchy. The first level of partitioning is based on a range of values, as for range partitioning; the second level is based on discrete values, as for list partitioning. This form of composite partitioning is
well suited for historical data, but allows you to further group the rows of data based on unordered or unrelated column values.
When creating range-list partitions, you specify the following:
Partitioning method: range Partitioning column(s) Partition descriptions identifying partition bounds Subpartitioning method: list Subpartitioning column Subpartition descriptions, each specifying a list of literal values (a value list),
which are the discrete values of the subpartitioning column that qualify a row to be included in the subpartition
Managing Partitions
* If I'm going to delete a tablespace with partitions:alter table xxx truncate partition part_namealter table xxx drop partition part_namedrop tablespace xxx
* Adding Partitions in the middle = Alter table xxx split partition part_name
* Split Partitions = Alter table xxx split partition part_vieja as (values) into (partition new_name, partition new_name); * Convert a Partition in a full table = alter table xx exchange partition part_name with table_new_no_part
* The views USER_TAB_PARTITIONS y USER_IND_PARTITIONS will show the range of partitions
* To Analyze a partition table or a partition index::analyxe table xxx partition (part_name) compute statistics;analyze index xxx partitio (part_name)compute;
* It's better to analyze the tables by partitions
* To import/export partition you should use table_name:part_name
