leaves12138 commented on code in PR #7976:
URL: https://github.com/apache/paimon/pull/7976#discussion_r3307898474


##########
docs/docs/spark/sql-write.md:
##########
@@ -221,6 +221,20 @@ WHEN NOT MATCHED THEN
 INSERT *      -- when not matched, insert this row without any transformation;
 ```
 
+### Column Alignment
+
+Assignments are aligned to the target by column name, and unmentioned target 
columns are filled with NULL.
+
+`INSERT *` / `UPDATE SET *` expand against the target columns:
+
+- Source columns missing from the target are rejected by default. Enable 
`spark.paimon.write.merge-schema` to keep them and evolve the table schema at 
write time (see [Write Merge Schema](#write-merge-schema)).

Review Comment:
   This section does not seem to match the implementation and the new tests. 
For top-level source-only columns under  / , strict mode currently drops them 
(for example ), while  evolves the target schema. Conversely, for target-only 
columns missing from the source, strict  /  throws, and only merge-schema mode 
preserves the target value for  or fills default/NULL for . Could you adjust 
these bullets to describe those four cases explicitly?



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