init

pg_include/nodes/params.h

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+/*-------------------------------------------------------------------------
+ *
+ * params.h
+ *	  Support for finding the values associated with Param nodes.
+ *
+ *
+ * Portions Copyright (c) 1996-2012, 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 */