sorting MQL translation

[NathanQingyangXu]

https://jira.mongodb.org/browse/HIBERNATE-68

Since last PR, null value supporting was disabled, so this PR excludes null value sorting out of the scope.

Note that MQL only supports sorting specification based on field path, not ad-hoc function invocation result on field as the following HQL:

from Book order by length(title)

However, by tapping into $addField (or $set as its alias) aggregate stages, we could emulate such HQL. A separate ticket was created at https://jira.mongodb.org/browse/HIBERNATE-79 to track this unfinished feature (not complete solution for it depends on whether the SQL function has its MQL operator counterpart).

HQL's sorting doc is at https://docs.jboss.org/hibernate/orm/6.6/userguide/html_single/Hibernate_User_Guide.html#hql-order-by.

This PR focuses on basic sorting semantic; the next followup ticket will tackle the Limits/Offsets (https://docs.jboss.org/hibernate/orm/6.6/userguide/html_single/Hibernate_User_Guide.html#hql-limit-offset).

[NathanQingyangXu]

The above visitor implementation deserves some explanation. It is used for the following HQL involving sorting using "select expression" as sort key name:

select b.title as title, b.publishYear as year from Book as b order by year desc, title asc

without implementing the visitor method, the above valid HQL won't work. The corresponding testing case is SortingIntegrationTests#testSortFieldByAlias().

The implementation is inspired by AbstractSQLTranslator in Hibernate as below (https://github.com/hibernate/hibernate-orm/blob/main/hibernate-core/src/main/java/org/hibernate/sql/ast/spi/AbstractSqlAstTranslator.java#L7158):

	@Override
	public void visitSqlSelectionExpression(SqlSelectionExpression expression) {
		if ( dialect.supportsOrdinalSelectItemReference() ) {
			appendSql( expression.getSelection().getJdbcResultSetIndex() );
		}
		else {
			expression.getSelection().getExpression().accept( this );
		}
	}

the first logic branch is about using ordinal reference as below:

select title, address from Contact order by 1 ASC, 2 DEC;

Given we have to translate to MQL which doesn't support native ordinal reference, so we have to use the second logic branch. Luckily regardless of whether oridnal preference is used or not, the current implementation works invariably.

I added a testing case (SortingIntegrationTests#testSortFieldByOrdinalReference) to prove that ordinal reference works without further ado (as long as we chose the second logic branch):

[NathanQingyangXu]

MongoDB puts null to the top in ASC case (only after MinKey ) as per https://www.mongodb.com/docs/manual/reference/bson-type-comparison-order/#std-label-bson-types-comparison-order

However, there is no counterpart of HQL's NULLS LAST and I am not sure whether the NULLS FIRST corresponds to Mongo's behaviour. My understanding is we could simply throw exception to avoid confusion.

Another alternative is to only throw exception when NULLS LAST is specified in HQL, provided NULLS FIRST is just what Mongo is doing. Not sure whether the precondition holds or not.

[NathanQingyangXu]

compared with Hibernate's default visitTuple implementation, our implementation is less elegant for we need to return value and currently we only support field path tuple, so the following common value type tuple usage is not supported for now:

insert into books (id, title) values (1, "War and Peace"), (2, "Crime and Punishment"), ...

[NathanQingyangXu]

I refactored the tuple visiting logic to make it generic. Now it will return collection of Expression, so it will be solid to work in any scenario.

[NathanQingyangXu]

This is an approach I found we could limit Hibernate property configuration in one testing method (the setting won't be applied to the whole class for it would break all the testing cases) using hibernate-testing and JUnit5's @Nested features.

[NathanQingyangXu]

@stIncMale could you take a new look at the PR? It was approved by the primary reviewer already; but its merging still requires secondary reviewer's approval.

[katcharov]

Let's use a nicely-formatted multi-line string for all of these.

Since you are using parameters, let's use .formatted( to set the parameter in the string (you do this in other tests).

[NathanQingyangXu]

good point! Committed at 8042163

Will create a quick PR without ticket later to fix similar issue in existing SimpleSelectQueryIntegrationTests.

[NathanQingyangXu]

Given the refactoring in SimpleSelectQueryIntegrationTests is easy to verify, I included it at a2cef52

[NathanQingyangXu]

Note that another palantir formatting issue was flushed out (.formatted() will be formatted in a new line, not right after the ending triple quotes of the text block). I solved this format issue at another PR: #97

[katcharov]

Maybe use AstSortOrder?

[NathanQingyangXu]

That was my original usage, but @stIncMale told me that is internal stuff so we'd better avoid using it. see #90 (comment) for the previous solved comment.

[stIncMale]

The last reviewed commit is a2cef52.

[stIncMale]

The last reviewed commit is 9e9ca6c.

[stIncMale]

The last reviewed commit is 019d5c0.