MDEV-31022: SIGSEGV in maria_create from create_internal_tmp_tablebb-11.0-MDEV-31022-variant3

The code in create_internal_tmp_table() didn't take into account that
now temporary (derived) tables may have multiple indexes:

- one index due to duplicate removal
   = In this example created by conversion of big-IN(...) into subquery
   = this index might be converted into a "unique constraint" if the field(s)
     length is too large.
- one index added by derived_with_keys optimization.

Make it handle multiple indexes.

As a consequence of this, remove TABLE_SHARE::uniques and replace it with
per-index HA_UNIQUE_HASH flag.
- TABLE_SHARE::uniques made sense when it referred to the only index in the
  table.
- Now, we need to know which of table indexes should be a unique constraint,
  so we indicate that as an index flag.

This patch is based on Monty's patch:
Co-Author: Monty <monty@mariadb.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/mysql-test/main/derived.test b/mysql-test/main/derived.test
index e5f01e15821..b26472d41c0 100644
--- a/mysql-test/main/derived.test
+++ b/mysql-test/main/derived.test
@@ -1244,5 +1244,29 @@ SELECT a FROM t1 WHERE a IN ( 1, 1, 2, 194 );
 drop table t1;
 
 --echo #
+--echo # MDEV-31022: SIGSEGV in maria_create from create_internal_tmp_table
+--echo # keydef incorrectly allocated on the stack in create_internal_tmp_table()
+--echo #
+
+CREATE TABLE t1 (c CHAR(1) NULL) ENGINE=MyISAM;
+INSERT INTO t1 (c) VALUES (1);
+SET statement
+  optimizer_where_cost=1,
+  big_tables=1,
+  in_predicate_conversion_threshold=2
+FOR
+SELECT * FROM t1 WHERE c IN ('','');
+
+SET statement
+  optimizer_where_cost=1,
+  big_tables=1,
+  in_predicate_conversion_threshold=2,
+  sql_mode=''
+FOR
+SELECT * FROM t1 WHERE c IN ('','');
+
+DROP TABLE t1;
+
+--echo #
 --echo # End of 11.0 tests
 --echo #