normanj-bitquill commented on code in PR #3828:
URL: https://github.com/apache/calcite/pull/3828#discussion_r1663134348
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core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java:
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@@ -1900,6 +1902,60 @@ private static class GreatestConvertlet implements
SqlRexConvertlet {
}
}
+ /** Convertlet that converts {@code GREATEST} and {@code LEAST}. */
+ private static class GreatestPgConvertlet implements SqlRexConvertlet {
+ @Override public RexNode convertCall(SqlRexContext cx, SqlCall call) {
Review Comment:
An expression like `GREATEST(1, 2, ...)` is compiled and becomes a `SqlCall`
object with arguments. The convertlet will then replace the `SqlCall` object
with a new `SqlCall` for `CASE`. We are only manipulating objects after they
are parsed, we do not generate SQL text and parse it again.
This will still explode original expression and use potentially much more
memory.
With simple integer arguments, this PR works with at least 1000 values.
If no limit is in place, the user is still restricted by the max query
length and what will fit in memory after the convertlet is run.
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