I have around 600 tables. How to drop list partition from oracle table without dropping table structure.
ALTER TABLE table DROP PARTITION partition_name;
or
DELETE FROM table PARTITION(partition_name);
I understand that you want to drop them not truncate, otherwise, you must replace DROP by TRUNCATE.
If you want to remove all partitions automatically.
Create a CURSOR, sharing information of ALL_TAB_PARTITIONS.
After the CURSOR create a LOOP to move into the table partitions.
If that can helps you, ask me and I give you more details.
Related
Does drop table command in hive also drop partitions?
I just want to know that or we have to use alter table table_name drop partition() command for this?
DROP TABLE statement always drops partitions metadata for both MANAGED and EXTERNAL tables because partitions can not exist without table. But for EXTERNAL tables it does not drop data in the filesystem.
If table is MANAGED, then DROP TABLE will delete table and partitions metadata and data in table location as well, all the table location including partition sub-folders.
If the table is EXTERNAL, it will drop only table definition in metadata and partition definitions, table location with data, including all partition folders will remain as is, and you can again create table on top of the same location and recover partitions.
The same is applicable for DROP PARTITION: if table is MANAGED, it will remove partition metadata along with partition sub-folder. And if table is EXTERNAL, partition sub-folder with data will remain, only partition metadata will be deleted.
So, for MANAGED tables, you do not need to delete data after dropping table or partition.
See also DROP TABLE and DROP PARTITION manual for more details.
I am not sure about altering a table to create a new partition as I am afraid I will lose data. If a table in an Oracle SQL DB is already partitioned but I am adding a new partition, will the existing data in the table be deleted?
No you dont lose the data
You can create list partition and expand it on default partition
for example if your partion is date:
alter table your_table split partition PDEFAULT values(TO_DATE('20161206','yyyymmdd')) into ( partition P20161206,partition PDEFAULT)
The only ALTER TABLE partitioning commands that can destroy data are DROP and TRUNCATE.
The EXCHANGE partition command can move data from a table partition to a different table, and vice-versa.
ADD, MOVE, COALESCE, RENAME, SPLIT, and MERGE do not change the table's data, although COALESCE, SPLIT, and MERGE can change the partition or subpartition in which data is stored.
I need to prepare the script to increase the partition range if the partition is going to get finished in next 2-3 months. How to find the existing table partition and we can edit to existing table or we need to create a new script.
Appreciate response
How to find the existing table partition
You could either generate the table DDL using DBMS_METADATA package to get the complete table DDL.
Or, query the user_tab_partitions view to get the table partition information.
To add new partitions, you need to use ADD PARTITION clause:
ALTER TABLE <table_name>
ADD PARTITION <new_partition>
VALUES (<new_value>)
TABLESPACE <tablespace_name>;
I have a students table in postgres that is populated via an external source. Each night we populate the students_swap table, and then after the long running operation is complete we rename it to students and the original table then becomes students_swap to be used the next day.
The problem with this is that when we add a new column or index to the original table we must remember to also do so on the swap table. I am attempting to automate some of this w/ the following:
-- Drop the swap table if it's already there...
DROP TABLE IF EXISTS students_swap;
-- Recreate the swap table using the original as a template...
CREATE TABLE students_swap AS SELECT * FROM students WHERE 1=2;
... populate the swap table ....
ALTER TABLE students RENAME TO students_temp;
ALTER TABLE students_swap RENAME TO ps_students;
ALTER TABLE students_temp RENAME TO students_swap;
This works well for creating the table structure but no indices are created for the swap table.
My question is how do I copy all of the indexes in addition to the table structure to make sure my original table and swap table stay in sync?
Use create table ... like instead:
CREATE TABLE students_swap (LIKE students INCLUDING ALL);
This will include indexes, primary keys and check constraints but will not re-create the foreign keys.
Edit:
INCLUDING ALL will also copy the default settings for columns populated by sequences (e.g. a column defined as serial). It sounds as if you want that. If you do not want that, then use INCLUDING INDEXES INCLUDING CONSTRAINTS instead.
Query:
Delete from test_table; (i am using this delete command in Procedure to perform daily)
This table contains 2 column name like scenario_id, item_id, these 2 column are composite primary key. So Each scenario_id will have 2 millions item_id, How to delete this table quicky.
The fastest way to delete the table might be DROP TABLE test_table command, and recreate the table using CREATE TABLE... command. DROP TABLE... will drop the table immediately. Well, actually it will move the table into recyclebin. You should PURGE RECYCLEBIN if want to completely remove the table.
Other way to delete the data in the table is to use TRUNCATE TABLE.... This is a little slower than DROP TABLE..., however, much faster than DELETE FROM.... Since there's no way to rollback the data after you truncate the table, you should be careful when you use TRUNCATE TABLE.
Check if there are any Foreign keys pointing onto this table. If they are, there MUST be indexes on these referring columns. Otherwise maintenance of the referential integrity will take ages
(Transactional) Delete on Oracle is slow by nature. Simple because of deleted data must be copied into UNDO tablespace, REDO logs and also archived REDO logs. This is the way how Oracle protects your data.
If our are deleting more than 50% of data, it is much faster when you simply create new table as select * from old_table where ... and then drop the new old one and rename new to old.
You can achieve similar goal by exchanging partitions in the partitioned table.
Or you can simply drop table's partitions if your table is partitioned wisely