feat: support expressions for count and offset in the Fetch operator

substrait-io · Nov 22, 2024 · 3b25a08 · 3b25a08
1 parent 708a7b8
commit 3b25a08
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Showing 2 changed files with 22 additions and 10 deletions.
diff --git a/proto/substrait/algebra.proto b/proto/substrait/algebra.proto
@@ -267,11 +267,23 @@ message CrossRel {
 message FetchRel {
   RelCommon common = 1;
   Rel input = 2;
-  // the offset expressed in number of records
-  int64 offset = 3;
-  // the amount of records to return
-  // use -1 to signal that ALL records should be returned
-  int64 count = 4;
+  oneof offset_mode {
+    // the offset expressed in number of records
+    // Deprecated: use `offset_expr` instead
+    int64 offset = 3 [deprecated = true];
+    // Expression evaluated into an integer specifying the number of records to
+    // skip.
+    Expression offset_expr = 5;
+  }
+  oneof count_mode {
+    // the amount of records to return
+    // use -1 to signal that ALL records should be returned
+    // Deprecated: use `count_expr` instead
+    int64 count = 4 [deprecated = true];
+    // Expression evaluated into an integer specifying the number of records to
+    // return. -1 signals that all records should be returned.
+    Expression count_expr = 6;
+  }
   substrait.extensions.AdvancedExtension advanced_extension = 10;
 }
 

diff --git a/site/docs/relations/logical_relations.md b/site/docs/relations/logical_relations.md
@@ -338,11 +338,11 @@ The fetch operation eliminates records outside a desired window. Typically corre
 
 ### Fetch Properties
 
-| Property | Description                                                           | Required                 |
-| -------- | --------------------------------------------------------------------- | ------------------------ |
-| Input    | A relational input, typically with a desired orderedness property.    | Required                 |
-| Offset   | A non-negative integer. Declares the offset for retrieval of records. | Optional, defaults to 0. |
-| Count    | A non-negative integer or -1. Declares the number of records that should be returned. -1 signals that ALL records should be returned. | Required |
+| Property          | Description                                                                                                                                                            | Required                 |
+|-------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------| ------------------------ |
+| Input             | A relational input, typically with a desired orderedness property.                                                                                                     | Required                 |
+| Offset Expression | An expression which evaluates to a non-negative integer. Declares the offset for retrieval of records.                                                                 | Optional, defaults to 0. |
+| Count Expression  | An expression which evaluates to a non-negative integer or -1. Declares the number of records that should be returned. -1 signals that ALL records should be returned. | Required |
 
 === "FetchRel Message"