MySQL compatibility: support 'is not distinct from' in join on section, pt1

[vdimir]

Changelog category (leave one):

• New Feature

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

• Support function isNotDistinctFrom in join on section for null-safe comparison, ref MySQL compatibility: <=> support and JOIN ON conditions #53061

Comment for reviewer: PR contains bunch of added lines, but significant part of them related to test reference file, or to moving FunctionTuple into header file, essential changes in code is not really big.

Test reference is taken from the result of the same test queries from another dbms that supports <=> operator in JOIN ON.

TODO:

• documentation
• add more sophisticated tests (different algorithms, join_use_nulls, column name clashes , etc)
• support in new analyzer (probably next PR) Analyzer support 'is not distinct from' in join on section #54068
• support syntax a <=> b and a IS NOT DISTINCT FROM b (next PR) Parse IS NOT DISTINCT and <=> operators #54067
• Implement function to support execution of operator as a regular expression in SELECT list

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[novikd]

LGTM

[UnamedRus]

Hm, so it's implemented as simple: tuple(null_column) = tuple(null_column)

[vdimir]

so it's implemented as simple: tuple(null_column) = tuple(null_column)

yes, initial idea was to introduce some new type of column or wrapper for CollumnNullable that will not be treated by algorithms in a special way. Wrapping with tuple matches this requirement. However, semantically it should be correct.

[UnamedRus]

Does it affect performance? (ie more complex hashtable)
And potential optimizations? (lets imagine pushdown of WHERE when condition match JOIN key)

[vdimir]

Does it affect performance? (ie more complex hashtable)

It can a bit, since for tuples hashed key type is used, while key type can be just UInt.

And potential optimizations? (lets imagine pushdown of WHERE when condition match JOIN key)

Potentiality yes, especially in cases when we just do not handle added step during plan optimization.

With filter push-down it works fine:

EXPLAIN PLAN

EXPLAIN PLAN SELECT * FROM t1 JOIN t2 ON t1.key = t2.key WHERE t1.key = 1 AND t2.key = 1;

┌─explain───────────────────────────────────────────────────────────────────────────────────────┐
│ Expression ((Projection + (Before ORDER BY + )))                                              │
│   Join (JOIN FillRightFirst)                                                                  │
│     Filter (( + Before JOIN))                                                                 │
│       ReadFromMergeTree (default.t1)                                                          │
│     Filter (( + (Joined actions + (Rename joined columns + (Projection + Before ORDER BY))))) │
│       ReadFromMergeTree (default.t2)                                                          │
└───────────────────────────────────────────────────────────────────────────────────────────────┘

EXPLAIN PLAN SELECT * FROM t1 JOIN t2 ON t1.key <=> t2.key WHERE t1.key = 1 AND t2.key = 1;

┌─explain─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ Expression ((Projection + (Before ORDER BY + )))                                                                                    │
│   Join (JOIN FillRightFirst)                                                                                                        │
│     Expression (( + (Convert JOIN columns + Before JOIN)))                                                                          │
│       Filter ((( + (Convert JOIN columns + Before JOIN)))[split])                                                                   │
│         ReadFromMergeTree (default.t1)                                                                                              │
│     Expression (( + (Convert joined columns + (Joined actions + (Rename joined columns + (Projection + Before ORDER BY))))))        │
│       Filter ((( + (Convert joined columns + (Joined actions + (Rename joined columns + (Projection + Before ORDER BY))))))[split]) │
│         ReadFromMergeTree (default.t2)                                                                                              │
└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

But I assume it can break in case of full_sorting_merge and read in order. For support that we need to check that tuple is defined as monotonic and handle it properly.

Basically it works the same as with joining different types, e.g. JOIN ON (t1.a :: UInt32) == (t2.a :: Int32) in that case type conversion step is added

[UnamedRus]

I assume, it will also break with #53443

[vdimir]

I assume, it will also break with #53443

Tests will catch it