1 files changed, 70 insertions, 0 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 24ade6cc201..bf4e81f554a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -5493,6 +5493,26 @@ get_utility_query_def(Query *query, deparse_context *context)
 	}
 }
 
+/*
+ * GetSpecialCustomVar
+ *
+ * If a custom-scan provider uses a special varnode, this function will be
+ * called when deparsing; it should return an Expr node to be reversed-listed
+ * in lieu of the special Var.
+ */
+static Node *
+GetSpecialCustomVar(CustomScanState *css, Var *varnode, PlanState **child_ps)
+{
+	Assert(IsA(css, CustomScanState));
+	Assert(IS_SPECIAL_VARNO(varnode->varno));
+
+	if (!css->methods->GetSpecialCustomVar)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("%s does not support special varno reference",
+						css->methods->CustomName)));
+	return (Node *) css->methods->GetSpecialCustomVar(css, varnode, child_ps);
+}
 
 /*
  * Display a Var appropriately.
@@ -5522,6 +5542,8 @@ get_variable(Var *var, int levelsup, bool istoplevel, deparse_context *context)
 	int			netlevelsup;
 	deparse_namespace *dpns;
 	deparse_columns *colinfo;
+	PlanState  *child_ps = NULL;
+	Node	   *expr;
 	char	   *refname;
 	char	   *attname;
 
@@ -5546,6 +5568,29 @@ get_variable(Var *var, int levelsup, bool istoplevel, deparse_context *context)
 		colinfo = deparse_columns_fetch(var->varno, dpns);
 		attnum = var->varattno;
 	}
+	else if (IS_SPECIAL_VARNO(var->varno) &&
+			 IsA(dpns->planstate, CustomScanState) &&
+			 (expr = GetSpecialCustomVar((CustomScanState *) dpns->planstate,
+										 var, &child_ps)) != NULL)
+	{
+		deparse_namespace	save_dpns;
+
+		if (child_ps)
+			push_child_plan(dpns, child_ps, &save_dpns);
+		/*
+		 * Force parentheses because our caller probably assumed a Var is a
+		 * simple expression.
+		 */
+		if (!IsA(expr, Var))
+			appendStringInfoChar(buf, '(');
+		get_rule_expr((Node *) expr, context, true);
+		if (!IsA(expr, Var))
+			appendStringInfoChar(buf, ')');
+
+		if (child_ps)
+			pop_child_plan(dpns, &save_dpns);
+		return NULL;
+	}
 	else if (var->varno == OUTER_VAR && dpns->outer_tlist)
 	{
 		TargetEntry *tle;
@@ -5760,6 +5805,7 @@ get_name_for_var_field(Var *var, int fieldno,
 	AttrNumber	attnum;
 	int			netlevelsup;
 	deparse_namespace *dpns;
+	PlanState  *child_ps = NULL;
 	TupleDesc	tupleDesc;
 	Node	   *expr;
 
@@ -5834,6 +5880,30 @@ get_name_for_var_field(Var *var, int fieldno,
 		rte = rt_fetch(var->varno, dpns->rtable);
 		attnum = var->varattno;
 	}
+	else if (IS_SPECIAL_VARNO(var->varno) &&
+			 IsA(dpns->planstate, CustomScanState) &&
+			 (expr = GetSpecialCustomVar((CustomScanState *) dpns->planstate,
+										 var, &child_ps)) != NULL)
+	{
+		StringInfo		saved = context->buf;
+		StringInfoData	temp;
+		deparse_namespace save_dpns;
+
+		initStringInfo(&temp);
+		context->buf = &temp;
+
+		if (child_ps)
+			push_child_plan(dpns, child_ps, &save_dpns);
+		if (!IsA(expr, Var))
+			appendStringInfoChar(context->buf, '(');
+		get_rule_expr((Node *) expr, context, true);
+		if (!IsA(expr, Var))
+			appendStringInfoChar(context->buf, ')');
+		if (child_ps)
+			pop_child_plan(dpns, &save_dpns);
+		context->buf = saved;
+		return temp.data;
+	}
 	else if (var->varno == OUTER_VAR && dpns->outer_tlist)
 	{
 		TargetEntry *tle;