Rename to single join to match general use.

proto/substrait/algebra.proto

@@ -444,7 +444,7 @@ message Rel {
     HashJoinRel hash_join = 13;
     MergeJoinRel merge_join = 14;
     NestedLoopJoinRel nested_loop_join = 18;
-    SingleMatchJoinRel single_match_join = 22;
+    SingleJoinRel single_join = 22;
     ConsistentPartitionWindowRel window = 17;
     ExchangeRel exchange = 15;
     ExpandRel expand = 16;
@@ -726,10 +726,9 @@ message NestedLoopJoinRel {
   substrait.extensions.AdvancedExtension advanced_extension = 10;
 }
 
-// A single match join where it as an error for there to be more than one match between the left and right inputs.
-// Typical use would be to have one side's duplicates eliminated and then be pushed into a column scan on the other
-// side.  This is a common join used while converting subqueries into joins.
-message SingleMatchJoinRel {
+// A single join enforces that each row is matched at once most counterpart.
+// If this constraint is violated, an error is raised.
+message SingleJoinRel {
   RelCommon common = 1;
   Rel left = 2;
   Rel right = 3;

site/docs/relations/physical_relations.md

@@ -73,7 +73,7 @@ The merge equijoin does a join by taking advantage of two sets that are sorted o
 
 
 
-## Single Match Join Operator
+## Single Join Operator
 
 The single match join works by enforcing that each row is involved in only a single match.  If this violated, an error
 is raised.  Typical use would be to have one side's duplicates eliminated and then be pushed into a column scan on the
@@ -86,7 +86,7 @@ other side. This operator is useful when converting subqueries into joins.
 | Property Maintenance | Distribution is maintained. Orderedness is eliminated.       |
 | Direct Output Order  | Same as the [Join](logical_relations.md#join-operator) operator. |
 
-### Single Match Join Properties
+### Single Join Properties
 
 | Property         | Description                                                                                                                                                                          | Required                                                    |
 |------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------|