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amount of data loss is acceptable, use off. Notice the red bold lettering above. Summary: If your data on security integrity and other requirements are not too high, you can use the method set to 0, after all, just "database may be damaged", as to the probability of damage to how big, I also do not know ... I haven't seen any damage yet, and I don't know when it will happen.Four, performance optimization Many people use it directly, and do not notice that SQLite also has configuration parameter

Postgresql pgbench tool pgbench is a benchmarking tool for PostgreSQL. pgbench is a performance benchmark tool provided by postgresql. You can use pgbench -- help to check the parameter Usage: pgbench [OPTIONS]... [DBNAME] Initialization options:-I invokes initialization mode-F NUM fill factor-s NUM scaling factorBenchmarking options:-c NUM number of concurrent database clients (default: 1) -C establish new connection for each transaction-d varname = VALUE define variable for use by custom scrip

the projection, and easily explains that the beam can pass through each other without interference. With regard to linear propagation and reflection, people quickly realized that the wavelength of light is very short, and in most cases, the behavior of light is still the same as that of classical particles. The diffraction experiment further proves this point. However, there is a basic difficulty in the theory of motion, that is, any fluctuation requires media to be transmitted. For example, so

"Idle list" to store the data you insert next time. The disk space is not lost, but the disk space is not returned to the operating system. If you delete a large amount of data and want to reduce the database file, run the VACUUM command. The vacuum command clears the "Idle list" and minimizes the database size. Note that vacuum takes some time (about 0.5 sec

. 1943 Allen · M. Turing (English) and other people designed and manufactured vacuum tube computer Colossus. Colossus is used to decipher the German code. The vacuum tube is easily burnt, but the maintenance is much less complex than the relay. Although the vacuum tube (microsecond) is 1000 times times faster than the relay (mil

own If you look confused, please skip this section for a moment. This is the result of the isset empty corresponding to the different variables, the difference between the two are gathered in this picture. The expression in the green dashed box isset , the yellow dashed box is !empty the performance. As can be seen, empty compared to isset need to judge more conditions, in order to determine the return result. If you don't understand a little bit, or can't remember all the details.

wisdom. In the rules of the rule there are five: a secret, such as the mantra, are transliteration. The second is to have more meaning, in China can not find the appropriate vocabulary, such as the Brahman, this name is more than righteousness. Three for China no, such as Sanfu, tree name, China no this tree. Four for Shun Gu, such as Ahan Doro three Miao qie three Bodhi. Five for respect, such as wisdom. Generally speaking, there are three kinds of wisdom, one for reality, the body of the

drainage consolidation method is mainly composed of two systems: drainage and pressurization. Drainage can take advantage of the Water Permeability of natural soil layer, especially the characteristics of the Multi-sanded Thin Layer in Shanghai, you can also set vertical drainage bodies such as sand wells, bagged sand wells and Plastic Drainage boards. Pressurization mainly involves the ground load method, vacuum preloading method, and well point pre

processing is necessary for obtaining multiple versions of concurrency control, and if the version of a tuple is still likely to be seen by other transactions, then that version of the tuple cannot be deleted. When a transaction commits, the expired tuple version will no longer be valid for the transaction, and the space it occupies must be recycled for use by other new tuples to avoid the endless need for disk space growth, where cleanup of the database is done by running

1. Seven temporary filesThe content is organized from http://sqlite.org/tempfiles.html.A different feature of SQLite is that a database consists of a single disk file. This simplifies the use of SQLite, because you only need to copy a single file to a mobile or backup database. This also makes SQLite suitable for application file format. However, when a database is stored in a single file, SQLite uses many temporary files during database processing.Currently, SQLite uses seven different types of

and well designed for their purpose. First of all, they was a very good fit, and it is a favorite remote enthusiasts. Vacuuming issue is not one of the sexiest made?? In house. It is therefore important to avoid life and pride in cleanliness. But the control of conventional dust bags and expensive nightmare, as well. This comment shows a preference for those involved in conducting a RegUlar practice to vacuum the floor for the inconvenience. In the e

, hair dryers, Power wiring boardsBefore we tested this large vacuum cleaner, the normal use of radiation has 15 μT, but it is not small. Currently, this small handheld vacuum cleaner is also popular. How big is its radiation? We also conducted a test. The handle distance is 0.03 m, 6.64 μm; the center of the left side is 4.22 μm; however, if you use this method, its radiation can be reduced to a safe range

')WHERE C.relhaspkey = ' F 'Order by C.relhaspkey, C.relname;EOF 'schemas= ' psql-t-a-c "$sql"-D $dbname |cut-d "|"-F 1 'tables= ' psql-t-a-c "$sql"-D $dbname |cut-d "|"-F 1 'For res in ' psql-t-a-c ' $sql '-D $dbname 'TodoSchema= ' echo $res |cut-d ' | "-F 1"Table= ' echo $res |cut-d ' | "-F 2"Tablename= ' echo ' $schema. $table "'PSQL-E-C "ALTER TABLE $tablename add primary key (ID)"-D $dbnameIf [$?-ne 0];thenecho "$dbname: Add primary key to $tablename error." >> $error _logFiDone The next e

Label:One, 7 types of temporary documentsA different feature of SQLite is that a database is composed of a single disk file. This simplifies the use of SQLite because moving or backing up a database simply copies a single file. This also makes SQLite suitable for use as an application file format. However, when you store a database in a single file, SQLite uses many temporary files during processing of the database.SQLite currently uses 7 different types of temporary files:* Rollback log (Rollba

| Pg_catalog | Pl/pgsql Procedural language(2 rows)testdb=# CREATE TABLE T_test (ID serial primary key, name text);CREATE TABLEtestdb=# CREATE index Idx_t_test_name on t_test (name);CREATE INDEXtestdb=# INSERT INTO T_test select Generate_series (1,100000), MD5 (Random ():: text);INSERT 0 100000testdb=# INSERT INTO T_test select Generate_series (100001,1000000), MD5 (Random ():: text);INSERT 0 900000testdb=# truncate t_test;TRUNCATE TABLEtestdb=# INSERT INTO T_test select Generate_series (1,1000

of waste battery processing fees be charged to each battery purchaser. (2) "wet processing"A "wet treatment" device is being built in the suburbs of Magdeburg. In addition to lead batteries, all kinds of batteries are dissolved in sulfuric acid, and various metals are extracted from the solution using ionic resins, the raw material obtained in this way is purer than the heat treatment method, so the price is higher in the market, and 95% of the various substances contained in the battery can be

system is discarded as invalid materials. Countermeasure: Adjust the picking position; Cause 4: vacuum,Due to insufficient air pressure, the vacuum tunnel is not smooth, and some guide blocks the vacuum tunnel.Or a vacuum leak causes insufficient air pressure and the device may not be able to pick up or drop it on th

: [NSDate date];[PickerView addSubview: DateP];// Initialize the PickerView to be hidden and give show a BOOL value to it. YESShow = YES;PickerView. hidden = YES;[Self. view addSubview: PickerView];}Give UIButton a click event and then change the show BOOL value:-(Void) click {If (show = YES ){PickerView. hidden = NO;Show = NO;} Else {PickerView. hidden = YES;Show = NO;}}Click "hide" and click "show ..This seems to be a BUG. BugThe Origin of "BUG:The original intention of Bug is "Bug" or "Bug ".

specified as the ANALYZE parameter, all tables and indexes in the database will be analyzed and statistical data will be generated.Sqlite> ANALYZE main;-- If you specify a table or index in the database as the ANALYZE parameter, the table and all its associated indexes will be analyzed.Sqlite> ANALYZE main. testtable;Sqlite> ANALYZE main. testtable_idx2;5. data cleanup: Compared with the VACUUM commands in PostgreSQL, their functions and implementati

preceding steps are required. If only the IC chip is attached, the preceding steps are canceled. Step 5: Stick the chip. Apply a proper amount of red glue (or black glue) to the IC position of the PCB printed circuit board, and then use anti-static equipment (vacuum suction pen or sub-) to correctly place the bare IC film on the red glue or black glue. Step 6: drying. Place the pasted bare slice in the thermal cycle oven and place it on the large pla