Jacob Williams 3d549f65f8 MDEV-38757 Fix EXCHANGE PARTITION with generated columns containing AND/OR conditions ...

EXCHANGE PARTITION fails with ERROR 1736 (Tables have different definitions)
when tables contain generated columns with AND/OR conditions, even when the
expressions are logically equivalent. This occurs because when expressions are
re-parsed (e.g., via CREATE TABLE ... LIKE), the order of arguments in AND/OR
conditions may change, but the comparison was order-sensitive.

The Item_cond::eq() method was implemented to perform set-based comparison
for commutative AND/OR operations. The set-based comparison algorithm ensures
that two Item_cond expressions are considered equal if they contain the same set
of equivalent arguments, regardless of order.

Added comprehensive test case covering:
- Generated columns with OR conditions
- Generated columns with AND conditions
- Multiple generated columns with different AND/OR combinations
- Nested AND/OR conditions

The fix allows EXCHANGE PARTITION to succeed when expressions are logically
equivalent but have different argument ordering, which is correct behavior
since AND/OR operations are commutative.

MDEV-38757 Limit unordered vcol condition comparison to EXCHANGE PARTITION

Review follow-up to the previous commit, which made Item_cond::eq()
compare AND/OR argument lists as sets for every caller. That changed
equality semantics globally and broke main.derived_cond_pushdown, where
conditions that eq() started reporting as equal were dropped from
attached_condition. Reordering AND/OR operands also changes evaluation
order, which is observable when operands are functions, so the relaxed
comparison must not be the default.

Item::Eq_config gains an unordered_conditions flag, defaulting to false,
next to the existing binary_cmp and omit_table_names flags.
Item_cond::eq() compares its argument lists as sets only when that flag
is set, and otherwise reports two distinct Item_cond objects as unequal,
as it did before this patch series. The flag is threaded through
Virtual_column_info::is_equal() and a new mysql_compare_tables()
parameter, and only Sql_cmd_alter_table_exchange_partition passes it as
true, so the relaxed comparison stays confined to the EXCHANGE PARTITION
metadata check.

The set comparison tests containment in both directions rather than
comparing element counts, so an expression also matches a form that
repeats one of its terms, for example

  col1 > 10 and col2 < 100 or col3 > 50
  col3 > 50 or col1 > 10 and col2 < 100 or col3 > 50

Test 5 of parts.partition_exchange_generated_columns covers that case.

2026-09-14 10:46:29 +03:00

9.6 KiB

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