typedef enum{ TBM_EMPTY, /* no hashtable, nentries == 0 */ TBM_ONE_PAGE, /* entry1 contains the single entry */ TBM_HASH /* pagetable is valid, entry1 is not */} TBMStatus;typedef struct PagetableEntry{ BlockNumber blockno; /* page number (hashtable key...
操作符is empty: 用于检测嵌套表是否为null。 操作符=和!=: 用于检测两个嵌套表是否相同。 函数cardinality:用于返回嵌套表变量的元素个数 submultiset of: 用于确定一个嵌套表是否为另一个嵌套表的子集 操作符member of:用于检测特定数据是否为嵌套表元素 操作符is a set: 用于检测嵌套表是否包含重复的元素值 em...
#define FLEXIBLE_ARRAY_MEMBER /* empty */ 1. 判断字段是否为空代码在 tupmacs.h,留待后面研究 /* * Check a tuple's null bitmap to determine whether the attribute is null. * Note that a 0 in the null bitmap indicates a null, while 1 indicates * non-null. */ #define att_isnull(AT...
*/ Assert(areq->callback_pending); return; } // 异步子计划已经获取到结果 // 如果子计划的返回结果槽为空,那么说明这个异步子计划的执行已经结束 // 递减剩余的异步子计划数量,然后返回 /* If the result is NULL or an empty slot, there's nothing more to do. */ if (TupIsNull(slot)) { ...
*/ } } /* Flush any remaining buffered tuples */ if (insertMethod != CIM_SINGLE) { if (!CopyMultiInsertInfoIsEmpty(&multiInsertInfo)) CopyMultiInsertInfoFlush(&multiInsertInfo, NULL, &processed); } /* ... */ return processed; }...
reservationVALUES(1108,'[2010-01-01 14:30, 2010-01-01 15:30)');--包含SELECTint4range(10,20)@>3;--重叠SELECTnumrange(11.1,22.2)&&numrange(20.0,30.0);--提取上边界SELECTupper(int8range(15,25));--计算交叉SELECTint4range(10,20)*int4range(15,25);--范围是否为空SELECTisempty(num...
(1108,'[2010-01-01 14:30, 2010-01-01 15:30)');--包含SELECT int4range(10,20)@>3;--重叠SELECT numrange(11.1,22.2)&&numrange(20.0,30.0);--提取上边界SELECT upper(int8range(15,25));--计算交叉SELECT int4range(10,20)*int4range(15,25);--范围是否为空SELECT isempty(numrange(1,5...
Many application designers have used the ZERO or EMPTY workaround, putting a zero or an empty value ‘’ to represent the absence of value .” Remember, empty isn’t NULL! This feature changes the behavior here. It now allows NULLs to be treated equally for the sake of distinct comparison...
pg_default | unmodifiable empty database| | | | | pg1=CTc/pg1 | | |template1 | pg1 | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/pg1 +| 7809 kB | pg_default | default template for new databases| | | | | pg1=CTc/pg1 | | |test | postgres | UTF8 | en_US.UTF-8 ...
30)'); -- 包含 SELECT int4range(10, 20) @> 3; -- 重叠 SELECT numrange(11.1, 22.2) && numrange(20.0, 30.0); -- 提取上边界 SELECT upper(int8range(15, 25)); -- 计算交叉 SELECT int4range(10, 20) * int4range(15, 25); -- 范围是否为空 SELECT isempty(numrange(1, 5)); ...