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From the ldquo;postgresqlmvccsource code example: www.linuxidc.comlinux2015-04257969.htm] rdquo;, we know that PG is not like From the last ldquo; PostgreSQL MVCC source code implementation [http://www.linuxidc.com/linux/2015-05/117969.htm?rdquo.pdf, we know that pgdoes not have From the previous article "PostgreSQL MVCC source code implementation []", we know that PG does not store the old version of undo like Oracle, but directly stores the old version in the relation file. The problem is

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First, restore disk space: In PostgreSQL, data rows that are deleted or updated using the Delete and UPDATE statements are not actually deleted, but only the state of the row is deleted or expired on the physical address of the old version of the data row. So when the data in the datasheet changes extremely frequently, the space that the table occupies will become very large after a period of time, but the amount of data may change little. To solve this problem, you need to periodically perform

PostgreSQL tutorial (14): database maintenance, postgresql tutorial I. Disk Space Restoration: In PostgreSQL, the data rows deleted or updated using the delete and update statements are not actually deleted, the physical address of the old data row sets the row status to deleted or expired. Therefore, when data in a data table changes frequently, the space occupied by the table will become large after a period of time, but the data volume may not change much. To solve this problem, you need to r

I. Disk Space Restoration: In PostgreSQL, the data rows deleted or updated using the delete and update statements are not actually deleted, the physical address of the old data row sets the row status to deleted or expired. Therefore, when data in a data table changes frequently, the space occupied by the table will become large after a period of time, but the data volume may not change much. To solve this problem, you need to regularly perform VACUUM

I. restore disk space In PostgreSQL, the data rows deleted or updated using the delete and update statements are not actually deleted, the physical address of the old data row sets the row status to deleted or expired. Therefore, when data in a data table changes frequently, the space occupied by the table will become large after a period of time, but the data volume may not change much. To solve this problem, you need to regularly perform vacuum op

delete data from SQLite, unused disk space is added to an internal "Idle list" to store the data you insert next time. The disk space is not lost. However, disk space is not returned to the operating system. (Hey hey, I mentioned this in sqlite.org's FAQ) Solution: 1. After the data is deleted, manually execute the VACUUM command. The execution method is simple. Objsqlhelper. executenonquery (commandtype. Text, "

Lagrangian density function of the model can not take quality term. But we know in the actual observation that electrons, protons, neutrons and other particles are of the mass, and that a large number of other elementary or non-elementary particles are of mass, while the vector particles that transmit the weak interactions: and the particles are also of the same quality. Theoretically, according to the requirements of symmetry (scalar potential can only be written in the form of 4-component com

Command 1. Sort databases: vacuum The vacuum command is an extended function of SQLite. It imitates the same commands in PostgreSQL. If vacuum is called with a table name or index name, the table or index will be sorted. In SQLite 1.0, the vacuum command callsGdbm_reorganize ()Sort back-end database files. Gdbm b

Pgbench is a database stress test tool that comes with PostgreSQL, supports the Tpc-b test model, or customizes the test model. Custom test models support meta-commands, invoke shell scripts, set random numbers, variables, and so on. 3 asynchronous interfaces supported [simple| Extended|prepared] Parameter Detailed list // Initial data parameters of the TPC-B test model. Initialization options: -i invokes initialization mode //Initial parameters -F NUM fill factor -n do not run

Label: SQLite3 performance tuning is achieved primarily through pragma directives. such as adjustment: Space release, disk synchronization, cache size, and so on. I. Space Release 1. How to query: PRAGMA auto_vacuum; Meaning: Query the auto-vacuum tag of the database. 2. Mark Meaning: Meaning of the auto-vacuum tag: Normally, when a transaction is committed that deletes data from the database, the database

dead rows. In aContinuous table, some rows are deleted or updated. These operations cause dead space ina table. Dead space can potentially was reused when new data is inserted. Due to a lot ofDead rows, bloating occurs. There is various reasons for index bloating, and it needs toBe fixed to achieve more performance, because it hurts the performance of the database.AUTO VACUUM is the best obviation from bloating, but it's a configurable parameter and

Sqlite3 performance adjustment is mainly achieved through The Pragma command. Such as space release, Disk Synchronization, and cache size adjustment. I. Space release1. How to query: Pragma auto_vacuum; Description: queries the auto-vacuum tag of a database. 2. Mark meaning: Description of auto-vacuum Tag:Normally, when a transaction is committed to delete data from the database, the database file size does

determine whether the query is visible (see the index_getnext function ). The transaction commit or rollback operation is simple. In addition to writing a transaction during the transaction commit, you only need to update the transaction status in the transaction commit log. That is to say, during rollback, the operations performed by the transaction do not need to be cleared physically. As long as the transaction status is set to rollback, the version generated by the transaction is naturally

beings in the world. Let us learn this method to improve evil and improve goodness. Free from suffering. This is also true. Bodhisattva. The Bodhi sect. Hua yanjue sentient beings. However, those who are called bodhisattvas are also omitted. Practitioners also practice. Deep prajna. It is also true. The cloud is also beyond the view of a wise person. When the Bodhisattva practices Prajna As you can see, all five are empty. View all the hardships and sorrows. Wuyun. Color recognition. Accumulate

release, Disk Synchronization, and Cache size.Do not open. As mentioned above, Vacuum is very inefficient!PRAGMA auto_vacuum;PRAGMA auto_vacuum = 0 | 1;Query or set the auto-vacuum tag of the database.Normally, when a transaction is committed to delete data from the database, the database file size does not change. Unused file pages are marked and used again in subsequent add operations. In this case, use

space to the operating system. (Hey,sqlite.org 's FAQ mentions the problem) Workaround: Two types of First, after the data is deleted, the vacuum command is executed manually, the execution method is very simple Objsqlhelper.executenonquery (CommandType.Text, "VACUUM") The vacuum command empties the "idle list" and compresses the database size to a m

It is mainly implemented through The Pragma command. For example, space release, Disk Synchronization, and cache size. Do not open. As mentioned above, vacuum is very inefficient! Pragma auto_vacuum;Pragma auto_vacuum = 0 | 1; Query or set the auto-vacuum tag of the database. Normally, when a transaction is committed to delete data from the database, the database file size does not change. Unused file pages

Directory Database query pre-preparation VACUUM ANALYZE Explain execution plan Two kinds of aggregation methods Association Re-distribution Query optimization Explain parameters Select the appropriate distribution key Partition table Compression table Grouping extensions Window functions column storage and row storage Functions and stored