官网文档说到 应该对外键建索引,但考虑到索引不是一定要的,而且类型有多种,所以不自动对外键建锁引,所以我们应该手动建 Adding a unique constraint willautomatically create a unique B-tree indexon the column or group of columns listed in the constraint. A uniqueness restriction covering only some rows ...
Set<String> uniqueLockKeys = new HashSet<String>(lockKeys); // filter empty keys Iterator<String> keyIterator = uniqueLockKeys.iterator(); while (keyIterator.hasNext()) { String key = keyIterator.next(); if (StringUtils.isEmptyNoOffset(key)) { keyIterator.remove(); } } if (CollectionUtils...
next_column_title TYPE_OF_DATA column_constraints, table_constraint table_constraint ) INHERITS existing_table_to_inherit_from; 除了先前定义中列出的列之外,还继承现有表中的所有列。括号内的部分分为两部分:列定义和表约束。 PostgreSQL列和表定义 列定义遵循以下语法模式: column_name data_type (optional_...
but the necessary information isnt available * until weve built baserel data structures and classified qual clauses. */joinlist = remove_useless_joins(root, joinlist);//清除无用的外连接/* * Also, reduce any semijoins with unique inner rels to plain inner joins. * Likewise...
UNIQUE constraint– ensure that values in a column or a group of columns are unique across the table. NOT NULL constraint– ensure values in a column are not NULL. DEFAULT constraint– specify a default value for a column using the DEFAULT constraint. ...
and table_constraint is: [ CONSTRAINT constraint_name ] { CHECK ( expression ) [ NO INHERIT ] | UNIQUE [ NULLS [ NOT ] DISTINCT ] ( column_name [, ... ] ) index_parameters | PRIMARY KEY ( column_name [, ... ] ) index_parameters | ...
] ) postgres=# alter tablespace test_tbs rename to prod_tbs; postgres=# alter tablespace test_tbs owner to test; --删除表空间 postgres=# \help drop tablespace Command: DROP TABLESPACE Description: remove a tablespace Syntax: DROP TABLESPACE [ IF EXISTS ] name postgres=# drop tablespace prod...
Note that phid is unique throughout a planner run, * not just within a query level --- this is so that we need not reassign ID's * when pulling a subquery into its parent. * * The idea is to evaluate the expression at (only) the ph_eval_at join level, * the...
* someday ... but see remove_unused_subquery_outputs to start with). */subquery =copyObject(subquery);//拷贝/* * If it's a LATERAL subquery, it might contain some Vars of the current * query level, requiring it to be treated as parameterized, even though ...
postgreSQL命令的词法分析和语法分析是由Unix工具Yacc和Lex制作的。使用的是 Bison 和 Flex。 前面已经分析了 词法分析器代码 这次介绍语法分析器代码 二、代码分析 由于词法分析器代码较多,文章只对其中部分做重点解说。 语法分析器gram.y ——定义段 /* src/backend/parser/gram.y */ /* 定义段 */ %{ #...