PostgreSQL数据库一些特征

1. 有关Postgresql一些极限值

极限值：

最大单个数据库大小	不限
最大数据单表大小	32 TB
单条记录最大	1.6 TB
单字段最大允许	1 GB
单表允许最大记录数	不限
单表最大字段数	250 - 1600 (取决于字段类型)
单表最大索引数	不限

详情阅读：http://www.postgres.cn/about

2. lcoks

URL:http://momjian.us/main/writings/pgsql/internalpics.pdf

见lock.h

/*
 * These are the valid values of type LOCKMODE for all the standard lock
 * methods (both DEFAULT and USER).
 */

/* NoLock is not a lock mode,but a flag value meaning "don't get a lock" */
#define NoLock					0

#define AccessShareLock			1		/* SELECT */
#define RowShareLock			2		/* SELECT FOR UPDATE/FOR SHARE */
#define RowExclusiveLock		3		/* INSERT,UPDATE,DELETE */
#define ShareUpdateExclusiveLock 4		/* VACUUM (non-FULL),ANALYZE,CREATE
										 * INDEX CONCURRENTLY */
#define ShareLock				5		/* CREATE INDEX (WITHOUT CONCURRENTLY) */
#define ShareRowExclusiveLock	6		/* like EXCLUSIVE MODE,but allows ROW
										 * SHARE */
#define ExclusiveLock			7		/* blocks ROW SHARE/SELECT...FOR
										 * UPDATE */
#define AccessExclusiveLock		8		/* ALTER TABLE,DROP TABLE,VACUUM
										 * FULL,and unqualified LOCK TABLE */

3.Postgresql major source code function

4. system tables

:comes from BruceMomjian

5.Offshoots of Postgres

: comes from Bruce Momjian