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/*-------------------------------------------------------------------------
*
* params.h
* Support for finding the values associated with Param nodes.
*
*
* Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/nodes/params.h
*
*-------------------------------------------------------------------------
*/
#ifndef PARAMS_H
#define PARAMS_H
/* To avoid including a pile of parser headers, reference ParseState thus: */
struct ParseState;
/* ----------------
* ParamListInfo
*
* ParamListInfo arrays 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_EXTERN parameter. The "paramid"
* of a PARAM_EXTERN Param can range from 1 to numParams.
*
* Although parameter numbers are normally consecutive, we allow
* ptype == InvalidOid to signal an unused array entry.
*
* pflags is a flags field. Currently the only used bit is:
* PARAM_FLAG_CONST signals the planner that it may treat this parameter
* as a constant (i.e., generate a plan that works only for this value
* of the parameter).
*
* There are two hook functions that can be associated with a ParamListInfo
* array to support dynamic parameter handling. First, if paramFetch
* isn't null and the executor requires a value for an invalid parameter
* (one with ptype == InvalidOid), the paramFetch hook is called to give
* it a chance to fill in the parameter value. Second, a parserSetup
* hook can be supplied to re-instantiate the original parsing hooks if
* a query needs to be re-parsed/planned (as a substitute for supposing
* that the current ptype values represent a fixed set of parameter types).
* Although the data structure is really an array, not a list, we keep
* the old typedef name to avoid unnecessary code changes.
* ----------------
*/
#define PARAM_FLAG_CONST 0x0001 /* parameter is constant */
typedef struct ParamExternData
{
Datum value; /* parameter value */
bool isnull; /* is it NULL? */
uint16 pflags; /* flag bits, see above */
Oid ptype; /* parameter's datatype, or 0 */
} ParamExternData;
typedef struct ParamListInfoData *ParamListInfo;
typedef void (*ParamFetchHook) (ParamListInfo params, int paramid);
typedef void (*ParserSetupHook) (struct ParseState *pstate, void *arg);
typedef struct ParamListInfoData
{
ParamFetchHook paramFetch; /* parameter fetch hook */
void *paramFetchArg;
ParserSetupHook parserSetup; /* parser setup hook */
void *parserSetupArg;
int numParams; /* number of ParamExternDatas following */
ParamExternData params[1]; /* VARIABLE LENGTH ARRAY */
} ParamListInfoData;
/* ----------------
* 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);
#endif /* PARAMS_H */
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