greenplumn value 源码
greenplumn value 代码
文件路径：/src/include/nodes/value.h
/*-------------------------------------------------------------------------
*
* value.h
* interface for Value nodes
*
*
* Copyright (c) 2003-2019, PostgreSQL Global Development Group
*
* src/include/nodes/value.h
*
*-------------------------------------------------------------------------
*/
#ifndef VALUE_H
#define VALUE_H
#include "nodes/nodes.h"
/*----------------------
* Value node
*
* The same Value struct is used for five node types: T_Integer,
* T_Float, T_String, T_BitString, T_Null.
*
* Integral values are actually represented by a machine integer,
* but both floats and strings are represented as strings.
* Using T_Float as the node type simply indicates that
* the contents of the string look like a valid numeric literal.
*
* (Before Postgres 7.0, we used a double to represent T_Float,
* but that creates loss-of-precision problems when the value is
* ultimately destined to be converted to NUMERIC. Since Value nodes
* are only used in the parsing process, not for runtime data, it's
* better to use the more general representation.)
*
* Note that an integer-looking string will get lexed as T_Float if
* the value is too large to fit in an 'int'.
*
* Nulls, of course, don't need the value part at all.
*----------------------
*/
typedef struct Value
{
NodeTag type; /* tag appropriately (eg. T_String) */
union ValUnion
{
int ival; /* machine integer */
char *str; /* string */
} val;
} Value;
#define intVal(v) (((Value *)(v))->val.ival)
#define floatVal(v) atof(((Value *)(v))->val.str)
#define strVal(v) (((Value *)(v))->val.str)
extern Value *makeInteger(int i);
extern Value *makeFloat(char *numericStr);
extern Value *makeString(char *str);
extern Value *makeBitString(char *str);
#endif /* VALUE_H */
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