[GitHub] [arrow] andygrove commented on a change in pull request #8738: ARROW-10685: [Rust] [DataFusion] Added support for Join on filter-pushdown optimizer.

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andygrove commented on a change in pull request #8738:
URL: https://github.com/apache/arrow/pull/8738#discussion_r528355857



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File path: rust/datafusion/src/optimizer/filter_push_down.rs
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@@ -54,116 +51,94 @@ is optimized to
     Projection: #a AS b
         Filter: #a Gt Int64(10)  <--- changed from #b to #a
 
-To perform such optimization, we first analyze the plan to identify three items:
-
-1. Where are the filters located in the plan
-2. Where are non-commutable operations' columns located in the plan (break_points)
-3. Where are projections located in the plan
-
-With this information, we re-write the plan by:
-
-1. Computing the maximum possible depth of each column between breakpoints
-2. Computing the maximum possible depth of each filter expression based on the columns it depends on
-3. re-write the filter expression for every projection that it commutes with from its original depth to its max possible depth
-4. recursively re-write the plan by deleting old filter expressions and adding new filter expressions on their max possible depth.
+This performs a single pass trought the plan. When it passes through a filter, it stores that filter,

Review comment:
       typo: "trought"




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