greenplumn variables 源码

greenplumn variables 代码

文件路径：/src/bin/psql/variables.h

/*
 * psql - the PostgreSQL interactive terminal
 *
 * Copyright (c) 2000-2019, PostgreSQL Global Development Group
 *
 * This implements a sort of variable repository.  One could also think of it
 * as a cheap version of an associative array.  Each variable has a string
 * name and a string value.  The value can't be NULL, or more precisely
 * that's not distinguishable from the variable being unset.
 *
 * src/bin/psql/variables.h
 */
#ifndef VARIABLES_H
#define VARIABLES_H

/*
 * Variables can be given "assign hook" functions.  The assign hook can
 * prevent invalid values from being assigned, and can update internal C
 * variables to keep them in sync with the variable's current value.
 *
 * An assign hook function is called before any attempted assignment, with the
 * proposed new value of the variable (or with NULL, if an \unset is being
 * attempted).  If it returns false, the assignment doesn't occur --- it
 * should print an error message with pg_log_error() to tell the user why.
 *
 * When an assign hook function is installed with SetVariableHooks(), it is
 * called with the variable's current value (or with NULL, if it wasn't set
 * yet).  But its return value is ignored in this case.  The hook should be
 * set before any possibly-invalid value can be assigned.
 */
typedef bool (*VariableAssignHook) (const char *newval);

/*
 * Variables can also be given "substitute hook" functions.  The substitute
 * hook can replace values (including NULL) with other values, allowing
 * normalization of variable contents.  For example, for a boolean variable,
 * we wish to interpret "\unset FOO" as "\set FOO off", and we can do that
 * by installing a substitute hook.  (We can use the same substitute hook
 * for all bool or nearly-bool variables, which is why this responsibility
 * isn't part of the assign hook.)
 *
 * The substitute hook is called before any attempted assignment, and before
 * the assign hook if any, passing the proposed new value of the variable as a
 * malloc'd string (or NULL, if an \unset is being attempted).  It can return
 * the same value, or a different malloc'd string, or modify the string
 * in-place.  It should free the passed-in value if it's not returning it.
 * The substitute hook generally should not complain about erroneous values;
 * that's a job for the assign hook.
 *
 * When a substitute hook is installed with SetVariableHooks(), it is applied
 * to the variable's current value (typically NULL, if it wasn't set yet).
 * That also happens before applying the assign hook.
 */
typedef char *(*VariableSubstituteHook) (char *newval);

/*
 * Data structure representing one variable.
 *
 * Note: if value == NULL then the variable is logically unset, but we are
 * keeping the struct around so as not to forget about its hook function(s).
 */
struct _variable
{
	char	   *name;
	char	   *value;
	VariableSubstituteHook substitute_hook;
	VariableAssignHook assign_hook;
	struct _variable *next;
};

/* Data structure representing a set of variables */
typedef struct _variable *VariableSpace;


VariableSpace CreateVariableSpace(void);
const char *GetVariable(VariableSpace space, const char *name);

bool		ParseVariableBool(const char *value, const char *name,
							  bool *result);

bool		ParseVariableNum(const char *value, const char *name,
							 int *result);

void		PrintVariables(VariableSpace space);

bool		SetVariable(VariableSpace space, const char *name, const char *value);
bool		SetVariableBool(VariableSpace space, const char *name);
bool		DeleteVariable(VariableSpace space, const char *name);

void		SetVariableHooks(VariableSpace space, const char *name,
							 VariableSubstituteHook shook,
							 VariableAssignHook ahook);

void		PsqlVarEnumError(const char *name, const char *value, const char *suggestions);

#endif							/* VARIABLES_H */

相关信息

greenplumn 源码目录

相关文章

greenplumn command 源码

greenplumn command 源码

greenplumn common 源码

greenplumn common 源码

greenplumn copy 源码

greenplumn copy 源码

greenplumn crosstabview 源码

greenplumn crosstabview 源码

greenplumn describe 源码

greenplumn describe 源码