Re: [PR] GH-41873: [Acero][C++] Reduce the asof-join overhead by minimizing copies of the left hand side [arrow]

["JerAguilon (via GitHub)" <gi...@apache.org>]

JerAguilon commented on code in PR #41874:
URL: https://github.com/apache/arrow/pull/41874#discussion_r1619106973


##########
cpp/src/arrow/acero/asof_join_node.cc:
##########
@@ -912,7 +912,12 @@ class CompositeTableBuilder {
         }
       }
     }
-    return CompositeTable{schema, inputs.size(), dst_to_src, pool};
+    // NB: The left hand side of the join (index 0) is the reference table of the
+    // asof-join. The output is comprised of continuous slices of the this table, so
+    // we can just take zero-copy slices of it. This is much faster than how other
+    // tables are treated, wherein we need to copy
+    return CompositeTable{schema, inputs.size(), dst_to_src, pool,
+                          /*contiguous_sources=*/{0}};

Review Comment:
   To aid review as this branch is rebased on top of https://github.com/apache/arrow/pull/41125
   
   This line is changed by this PR.



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