On 28-6-2014 10:43, Mark Rotteveel wrote: > On 28-6-2014 10:36, Dimitry Sibiryakov wrote: >> 28.06.2014 9:46, Mark Rotteveel wrote: >>> On 25-6-2014 15:21, Dimitry Sibiryakov wrote: >>>> This is right only for those who set up READ COMMITTED transaction >>>> isolation level >>>> which is not default. >>> >>> That is not true, READ_COMMITTED is the default in a lot of the Firebird >>> drivers (eg in Jaybird, Firebird .NET provider, fdb). >> >> In this case these drivers should be fixed to provide consistent data >> by default, not >> the engine. > > How about no. READ COMITTED is the default for a lot of other database > drivers for other DBMS as well, and usually matches the expectations of > users (which includes the occurrence of non-repeatable reads and phantom > reads).
But as a datapoint, PostgreSQL does this: "Read Committed is the default isolation level in PostgreSQL. When a transaction uses this isolation level, a SELECT query (without a FOR UPDATE/SHARE clause) sees only data committed before the query began; it never sees either uncommitted data or changes committed during query execution by concurrent transactions. In effect, a SELECT query sees a *snapshot* of the database as of the instant the query begins to run. However, SELECT does see *the effects of previous updates executed within its own transaction*, even though they are not yet committed. Also note that two successive SELECT commands can see different data, even though they are within a single transaction, if other transactions commit changes during execution of the first SELECT." source: http://www.postgresql.org/docs/current/static/transaction-iso.html Mark -- Mark Rotteveel ------------------------------------------------------------------------------ Open source business process management suite built on Java and Eclipse Turn processes into business applications with Bonita BPM Community Edition Quickly connect people, data, and systems into organized workflows Winner of BOSSIE, CODIE, OW2 and Gartner awards http://p.sf.net/sfu/Bonitasoft Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
