src/libpq/include/nodes/params.h

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/*-------------------------------------------------------------------------
 *
 * params.h
 *        Declarations of stuff needed to handle parameterized plans.
 *
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/include/nodes/params.h,v 1.28 2004/12/31 22:03:34 pgsql Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef PARAMS_H
#define PARAMS_H

#include "access/attnum.h"


/* ----------------
 * The following are the possible values for the 'paramkind'
 * field of a Param node.
 *
 * PARAM_NAMED: The parameter has a name, i.e. something
 *                              like `$.salary' or `$.foobar'.
 *                              In this case field `paramname' must be a valid name.
 *
 * PARAM_NUM:   The parameter has only a numeric identifier,
 *                              i.e. something like `$1', `$2' etc.
 *                              The number is contained in the `paramid' field.
 *
 * PARAM_EXEC:  The parameter is an internal executor parameter.
 *                              It has a number contained in the `paramid' field.
 *
 * PARAM_INVALID should never appear in a Param node; it's used to mark
 * the end of a ParamListInfo array.
 *
 * NOTE: As of PostgreSQL 7.3, named parameters aren't actually used and
 * so the code that handles PARAM_NAMED cases is dead code.  We leave it
 * in place since it might be resurrected someday.
 * ----------------
 */

#define PARAM_NAMED             11
#define PARAM_NUM               12
#define PARAM_EXEC              15
#define PARAM_INVALID   100


/* ----------------
 *        ParamListInfo
 *
 *        ParamListInfo entries are used to pass parameters into the executor
 *        for parameterized plans.      Each entry in the array defines the value
 *        to be substituted for a PARAM_NAMED or PARAM_NUM parameter.
 *
 *              kind   : the kind of parameter (PARAM_NAMED or PARAM_NUM)
 *              name   : the parameter name (valid if kind == PARAM_NAMED)
 *              id         : the parameter id (valid if kind == PARAM_NUM)
 *              ptype  : the type of the parameter value
 *              isnull : true if the value is null (if so 'value' is undefined)
 *              value  : the value that has to be substituted in the place
 *                               of the parameter.
 *
 *       ParamListInfo is to be used as an array of ParamListInfoData
 *       records.  A dummy record with kind == PARAM_INVALID marks the end
 *       of the array.
 * ----------------
 */

typedef struct ParamListInfoData
{
        int                     kind;
        char       *name;
        AttrNumber      id;
        Oid                     ptype;
        bool            isnull;
        Datum           value;
} ParamListInfoData;

typedef ParamListInfoData *ParamListInfo;


/* ----------------
 *        ParamExecData
 *
 *        ParamExecData entries are used for executor internal parameters
 *        (that is, values being passed into or out of a sub-query).  The
 *        paramid of a PARAM_EXEC Param is a (zero-based) index into an
 *        array of ParamExecData records, which is referenced through
 *        es_param_exec_vals or ecxt_param_exec_vals.
 *
 *        If execPlan is not NULL, it points to a SubPlanState node that needs
 *        to be executed to produce the value.  (This is done so that we can have
 *        lazy evaluation of InitPlans: they aren't executed until/unless a
 *        result value is needed.)      Otherwise the value is assumed to be valid
 *        when needed.
 * ----------------
 */

typedef struct ParamExecData
{
        void       *execPlan;           /* should be "SubPlanState *" */
        Datum           value;
        bool            isnull;
} ParamExecData;


/* Functions found in src/backend/nodes/params.c */
extern ParamListInfo copyParamList(ParamListInfo from);
extern ParamListInfo lookupParam(ParamListInfo paramList, int thisParamKind,
                        const char *thisParamName, AttrNumber thisParamId,
                        bool noError);

#endif   /* PARAMS_H */