mattmartin14 commented on code in PR #1534:
URL: https://github.com/apache/iceberg-python/pull/1534#discussion_r1949176655


##########
pyiceberg/table/upsert_util.py:
##########
@@ -0,0 +1,146 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+from pyarrow import Table as pyarrow_table
+import pyarrow as pa
+from pyarrow import compute as pc
+
+from pyiceberg.expressions import (
+    BooleanExpression,
+    And,
+    EqualTo,
+    Or,
+    In,
+)
+
+def create_match_filter(df: pyarrow_table, join_cols: list) -> 
BooleanExpression:
+
+    unique_keys = df.select(join_cols).group_by(join_cols).aggregate([])
+
+    if len(join_cols) == 1:
+        return In(join_cols[0], unique_keys[0].to_pylist())
+    else:
+        return Or(*[
+            And(*[
+                EqualTo(col, row[col])
+                for col in join_cols
+            ])
+            for row in unique_keys.to_pylist()
+        ])
+
+def has_duplicate_rows(df: pyarrow_table, join_cols: list) -> bool:
+    """
+    This function checks if there are duplicate rows in in a pyarrow table 
based on the join columns.
+    """
+   
+    return len(
+        df.select(join_cols)
+            .group_by(join_cols)
+            .aggregate([([], "count_all")])
+            .filter(pc.field("count_all") > 1)
+    ) > 0
+
+def get_rows_to_update(source_table: pa.Table, target_table: pa.Table, 
join_cols: list) -> pa.Table:
+    
+    """
+        This function takes the source_table, trims it down to rows that match 
in both source and target.
+        It then does a scan for the non-key columns to see if any are 
mis-aligned before returning the final row set to update
+    """
+    
+    all_columns = set(source_table.column_names)
+    join_cols_set = set(join_cols)
+
+    non_key_cols = list(all_columns - join_cols_set)
+
+    match_expr = None
+
+    for col in join_cols:
+        target_values = target_table.column(col).to_pylist()
+        expr = pc.field(col).isin(target_values)
+
+        if match_expr is None:
+            match_expr = expr
+        else:
+            match_expr = match_expr & expr
+    
+    matching_source_rows = source_table.filter(match_expr)
+
+    rows_to_update = []
+
+    for index in range(matching_source_rows.num_rows):
+        
+        source_row = matching_source_rows.slice(index, 1)
+
+        target_filter = None
+
+        for col in join_cols:
+            target_value = source_row.column(col)[0].as_py()  
+            if target_filter is None:
+                target_filter = pc.field(col) == target_value
+            else:
+                target_filter = target_filter & (pc.field(col) == target_value)
+
+        matching_target_row = target_table.filter(target_filter)
+
+        if matching_target_row.num_rows > 0:
+            needs_update = False
+
+            for non_key_col in non_key_cols:
+                source_value = source_row.column(non_key_col)[0].as_py()
+                target_value = 
matching_target_row.column(non_key_col)[0].as_py()
+
+                if source_value != target_value:

Review Comment:
   let's table this for now; i see what you are getting at; this is one of the 
core reasons why i wanted a compute engine like datafusion in the mix, because 
it's highly optimized to churn through arrow tables. Maybe we can get data 
fusion added later, since we had a working example using it.



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