vladimirg-db commented on code in PR #49658:
URL: https://github.com/apache/spark/pull/49658#discussion_r1940753136
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/resolver/ExpressionResolver.scala:
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@@ -288,30 +473,148 @@ class ExpressionResolver(
/**
* [[Literal]] resolution doesn't require any specific resolution logic at
this point.
+ */
+ private def resolveLiteral(literal: Literal): Expression = literal
+
+ /**
+ * The [[GetViewColumnByNameAndOrdinal]] is a special internal expression
that is placed by the
+ * [[SessionCatalog]] in the top [[Project]] operator of the freshly
reconstructed unresolved
+ * view plan. Since the view schema is fixed and persisted in the catalog,
we have to extract
+ * the right attributes from the view plan regardless of the underlying
table schema changes.
+ * [[GetViewColumnByNameAndOrdinal]] contains attribute name and it's
ordinal to perform the
+ * necessary matching. If the matching was not successful, or the number of
matched candidates
+ * differs from the recorded one, we throw an error.
+ *
+ * Example of the correct name matching:
+ *
+ * {{{
+ * CREATE TABLE underlying (col1 INT, col2 STRING);
+ * CREATE VIEW all_columns AS SELECT * FROM underlying;
+ *
+ * -- View plan for the SELECT below will contain a Project node on top with
the following
+ * -- expressions:
+ * -- getviewcolumnbynameandordinal(`spark_catalog`.`default`.`all_columns`,
col1, 0, 1)
+ * -- getviewcolumnbynameandordinal(`spark_catalog`.`default`.`all_columns`,
col2, 0, 1)
Review Comment:
That's how it's rendered in Spark logical plan.
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