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[CALCITE-6035] Unparse 'WITHIN GROUP' for BigQuery dialect to match BigQuery documentation #3466

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[CALCITE-6035] Unparse 'WITHIN GROUP' for BigQuery dialect to match BigQuery documentation #3466

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[CALCITE-6035] Unparse 'WITHIN GROUP' for BigQuery dialect to match B…
olivrlee Oct 13, 2023
21d2976
Fix style
olivrlee Oct 18, 2023
48d616d
Update style for :core:checkstyleTest
olivrlee Oct 20, 2023
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15 changes: 15 additions & 0 deletions core/src/main/java/org/apache/calcite/sql/dialect/BigQuerySqlDialect.java
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Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,9 @@ public BigQuerySqlDialect(SqlDialect.Context context) {
}
unparseItem(writer, call, leftPrec);
break;
case WITHIN_GROUP:
unparseWithinGroup(writer, call, leftPrec, rightPrec);
break;
default:
super.unparseCall(writer, call, leftPrec, rightPrec);
}
Expand Down Expand Up @@ -292,6 +295,18 @@ private static void unparseItem(SqlWriter writer, SqlCall call, int leftPrec) {
writer.endList(frame);
}

private static void unparseWithinGroup(SqlWriter writer, SqlCall call, int leftPrec,
int rightPrec) {
assert call.operandCount() == 2;
call.operand(0).unparse(writer, 0, 0);
writer.keyword("OVER");
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so I think you're more familiar with these clauses than me, is it guaranteed that the WITHIN GROUP translates to BQ's OVER in every case? are they really just synonyms for each other, I mean

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So I detailed in this comment how Calcite currently only supports
select percentile_cont(0.5) within group (order by X)
so I want to say that for what is supported at this moment, it is sufficient

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Ohhh ok. So if Calcite ended up supporting the partition by case (your input_2 from that comment), do you know if this would break?

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Julian had a comment here about how we should approach the followup tickets
I think it won't work out of the box, there are things to figure out
We would still be parsing it as within_group in the parser, but want it to be handled differently in the validator.

questions to then consider: would we still use a SqlWithinGroupOperator? If yes, then that would be unparsed into "OVER" correctly. If not, this may have to change

final SqlWriter.Frame orderFrame =
writer.startList(SqlWriter.FrameTypeEnum.ORDER_BY_LIST, "(", ")");
writer.keyword("ORDER BY");
call.operand(1).unparse(writer, 0, 0);
writer.endList(orderFrame);
}

private static TimeUnit validate(TimeUnit timeUnit) {
switch (timeUnit) {
case MICROSECOND:
Expand Down
13 changes: 13 additions & 0 deletions core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java
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Expand Up @@ -1294,6 +1294,19 @@ private static String toSql(RelNode root, SqlDialect dialect,
.withPostgresql().ok(expectedPostgresql);
}

@Test void testPercentileContWithinGroupClauseBigQuery() {
final String query = "select percentile_cont(0.5) WITHIN GROUP (ORDER BY `product_class_id`)\n"
+ "from `foodmart`.`product`";
final String expected = "SELECT PERCENTILE_CONT(0.5) OVER "
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I think the PERCENTILE_CONT function for BigQuery must have two arguments. I think this expected query would probably fail since the column isn't passed to the function directly as an argument

+ "(ORDER BY product_class_id NULLS LAST)\n"
+ "FROM foodmart.product";
final SqlParser.Config parserConfig =
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BigQuerySqlDialect.DEFAULT.configureParser(SqlParser.config());
final Sql sql = fixture()
.withBigQuery().withLibrary(SqlLibrary.BIG_QUERY).parserConfig(parserConfig);
sql.withSql(query).ok(expected);
}

/** Test case for
* <a href="https://issues.apache.org/jira/browse/CALCITE-2722">[CALCITE-2722]
* SqlImplementor createLeftCall method throws StackOverflowError</a>. */
Expand Down
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