lottu=# \h create index Command: CREATE INDEX Description: define a new index Syntax: CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] name ] ON table_name [ USING method ] ( { column_name | ( expression ) } [ COLLATE collation ] [ opclass ] [ ASC | DESC ] [ N...
PostgreSQL是自由的对象-关系型数据库服务器,在灵活的BSD风格许可证下发行。它在其他开放源代码数据库系统和专有系统之外,为用户又提供了一种选择。 我们还是建议您使用云数据库进行搭建,省去数据迁移等麻烦操作,数据库详见:https://cloud.tencent.com/pro... 在本文中,我们将讨论如何在postgreSQL接口中创建和管理表...
UNIQUE [ NULLS [ NOT ] DISTINCT ] ( column_name [, ... ] ) index_parameters | PRIMARY KEY ( column_name [, ... ] ) index_parameters | EXCLUDE [ USING index_method ] ( exclude_element WITH operator [, ... ] ) index_parameters [WHERE( predicate ) ] | FOREIGN KEY ( column_na...
Command: DROP SCHEMA Description: remove a schema Syntax: DROP SCHEMA [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ] 参数: IF EXISTS 如果模式不存在,不会抛出错误。 name 模式名称。 CASCADE 自动删除该模式下数据库对象。 RESTRICT 如果该模式下还存在数据库对象,则不允许删除该模式,RESTRICT为...
releases of PostgreSQL where this was the standard behavior. If INDEX_CLEANUP is set to ON, VACUUM will conservatively remove all dead tuples from indexes. INDEX_CLEANUP can also be set to OFF to force VACUUM to always skip index vacuuming, even when there are many dead tuples in the ...
避免在ReservePrivateRefCountEntry做内存分配,因为有时候会拿着spinlock调这个函数】 */ // 【一级缓存】:8个元素 static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES]; // 空闲位置index static uint32 PrivateRefCountClock = 0; // 指向数组中空余的位置 static PrivateRefCountEntry *...
支持SP-GiST覆盖索引功能满足任意维度聚集存储 场景: 地理信息、物联网、共享出行等使用了地理信息、JSON、range等数据类型的业务 价值: 将value集成到索引叶子结点, 减少block扫描, 提高基于空间、JSON、range的范围搜索的响应速度 DEMO: createindexidx_tbl_1ontblusingspgist (gis)include(col1,col2);-- 叶子结...
-> Index Scan using bmsql_stock_pkey_103384 on public.bmsql_stock_103384 bmsql_stock (cost=0.43..5.27 rows=1 width=4) (actual time=0.006..0.006 rows=0 loops=186) | Output: bmsql_stock.s_w_id, bmsql_stock.s_i_id, bmsql_stock.s_quantity, bmsql_stock.s_ytd, bmsql_stock.s_...
3、Remove old wal,计算两次checkpoint间的wal数量进行回收重用,并清理不再需要的wal /* * Update the average distance between checkpoints if the prior checkpoint * exists. */ if (PriorRedoPtr != InvalidXLogRecPtr) /*根据ptr偏移量,预估出两次checkpoint间产生的wal量CheckPointDistanceEstimate*/ ...
params->index_cleanup == VACOPT_TERNARY_DISABLED) nkeep += 1; else tupgone = true; /* we can delete the tuple */ all_visible = false; break; case HEAPTUPLE_RECENTLY_DEAD: /* * If tuple is recently deleted then we must not remove it ...