Allow DECLARE CURSOR to take parameters from the portal in which it is

executed.  Previously, the DECLARE would succeed but subsequent FETCHes
would fail since the parameter values supplied to DECLARE were not
propagated to the portal created for the cursor.
In support of this, add type Oids to ParamListInfo entries, which seems
like a good idea anyway since code that extracts a value can double-check
that it got the type of value it was expecting.
Oliver Jowett, with minor editorialization by Tom Lane.

src/backend/nodes/params.c

@@ -0,0 +1,122 @@
+/*-------------------------------------------------------------------------
+ *
+ * params.c
+ *	  Support functions for plan parameter lists.
+ *
+ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL: pgsql/src/backend/nodes/params.c,v 1.1 2004/08/02 01:30:42 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "nodes/params.h"
+#include "utils/datum.h"
+#include "utils/lsyscache.h"
+
+
+/*
+ * Copy a ParamList.
+ *
+ * The result is allocated in CurrentMemoryContext.
+ */
+ParamListInfo
+copyParamList(ParamListInfo from)
+{
+	ParamListInfo retval;
+	int i, size;
+
+	if (from == NULL)
+		return NULL;
+
+	size = 0;
+	while (from[size].kind != PARAM_INVALID)
+		size++;
+
+	retval = (ParamListInfo) palloc0((size + 1) * sizeof(ParamListInfoData));
+
+	for (i = 0; i < size; i++) {
+		/* copy metadata */
+		retval[i].kind = from[i].kind;
+		if (from[i].kind == PARAM_NAMED)
+			retval[i].name = pstrdup(from[i].name);
+		retval[i].id = from[i].id;
+		retval[i].ptype = from[i].ptype;
+
+		/* copy value */
+		retval[i].isnull = from[i].isnull;
+		if (from[i].isnull)
+		{
+			retval[i].value = from[i].value; /* nulls just copy */
+		}
+		else
+		{
+			int16 typLen;
+			bool  typByVal;
+
+			get_typlenbyval(from[i].ptype, &typLen, &typByVal);
+			retval[i].value = datumCopy(from[i].value, typByVal, typLen);
+		}
+	}
+
+	retval[size].kind = PARAM_INVALID;
+
+	return retval;
+}
+
+/*
+ * Search a ParamList for a given parameter.
+ *
+ * On success, returns a pointer to the parameter's entry.
+ * On failure, returns NULL if noError is true, else ereports the error.
+ */
+ParamListInfo
+lookupParam(ParamListInfo paramList, int thisParamKind,
+			const char *thisParamName, AttrNumber thisParamId,
+			bool noError)
+{
+	if (paramList != NULL)
+	{
+		while (paramList->kind != PARAM_INVALID)
+		{
+			if (thisParamKind == paramList->kind)
+			{
+				switch (thisParamKind)
+				{
+					case PARAM_NAMED:
+						if (strcmp(paramList->name, thisParamName) == 0)
+							return paramList;
+						break;
+					case PARAM_NUM:
+						if (paramList->id == thisParamId)
+							return paramList;
+						break;
+					default:
+						elog(ERROR, "unrecognized paramkind: %d",
+							 thisParamKind);
+				}
+			}
+			paramList++;
+		}
+	}
+
+	if (!noError)
+	{
+		if (thisParamKind == PARAM_NAMED)
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("no value found for parameter \"%s\"",
+							thisParamName)));
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("no value found for parameter %d",
+							thisParamId)));
+	}
+
+	return NULL;
+}