InnoDB
DROP TABLE automatically commits the current active transaction, unless you use the
Postgres - http://www.postgresql.org/docs/devel/static/mvcc.html
http://www.postgresql.org/docs/devel/static/mvcc-intro.html
1) MVCC == Multiversion Concurrency Control
2) The main advantage of using the MVCC model of concurrency control rather than locking is that in MVCC locks acquired for querying (reading) data do not conflict with locks acquired for writing data, and so reading never blocks writing and writing never blocks reading. PostgreSQL maintains this guarantee even when providing the strictest level of transaction isolation through the use of an innovative Serializable Snapshot Isolation (SSI) level.
3) Table- and row-level locking facilities are also available in PostgreSQL for applications which don't generally need full transaction isolation and prefer to explicitly manage particular points of conflict.
? http://www.postgresql.org/docs/devel/static/transaction-iso.html
DROP TABLE automatically commits the current active transaction, unless you use the
TEMPORARY keyword.Postgres - http://www.postgresql.org/docs/devel/static/mvcc.html
http://www.postgresql.org/docs/devel/static/mvcc-intro.html
1) MVCC == Multiversion Concurrency Control
2) The main advantage of using the MVCC model of concurrency control rather than locking is that in MVCC locks acquired for querying (reading) data do not conflict with locks acquired for writing data, and so reading never blocks writing and writing never blocks reading. PostgreSQL maintains this guarantee even when providing the strictest level of transaction isolation through the use of an innovative Serializable Snapshot Isolation (SSI) level.
3) Table- and row-level locking facilities are also available in PostgreSQL for applications which don't generally need full transaction isolation and prefer to explicitly manage particular points of conflict.
? http://www.postgresql.org/docs/devel/static/transaction-iso.html
Table 13-1. Standard SQL Transaction Isolation Levels
| Isolation Level | Dirty Read | Nonrepeatable Read | Phantom Read |
|---|---|---|---|
| Read uncommitted | Possible | Possible | Possible |
| Read committed | Not possible | Possible | Possible |
| Repeatable read | Not possible | Not possible | Possible |
| Serializable | Not possible | Not possible | Not possible |
In PostgreSQL, you can request any of the four standard transaction isolation levels
? a SELECT query (without a FOR UPDATE/SHARE clause)