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MDEV-39265: Assertion (mem_root->flags & 4) == 0 failed upon 2nd execution USING DEFAULT with sequence #4926

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MDEV-39265: Assertion (mem_root->flags & 4) == 0 failed upon 2nd execution USING DEFAULT with sequence #4926

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21 changes: 21 additions & 0 deletions mysql-test/main/ps_mem_leaks.result
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Original file line number Diff line number Diff line change
Expand Up @@ -367,4 +367,25 @@ a
# Clean up
DEALLOCATE PREPARE stmt;
DROP TABLE t1;
#
# MDEV-39265: Assertion `(mem_root->flags & 4) == 0` failed upon 2nd execution `USING DEFAULT` with sequence
#
CREATE SEQUENCE s;
CREATE TABLE t (a INT DEFAULT(NEXTVAL(s)));
INSERT INTO t VALUES (1), (2);
PREPARE stmt FROM "UPDATE t SET a = ?";
# Verify no SIGABRT
EXECUTE stmt USING 3;
EXECUTE stmt USING DEFAULT;
# Verify the there are no repeated allocations on statement mem_root
SET @saved_dbug = @@SESSION.debug_dbug;
SET SESSION debug_dbug="+d,assert_no_alloc_internal_tables";
EXECUTE stmt USING DEFAULT;
EXECUTE stmt USING 4;
EXECUTE stmt USING DEFAULT;
EXECUTE stmt USING DEFAULT;
SET SESSION debug_dbug= @saved_dbug;
DEALLOCATE PREPARE stmt;
DROP SEQUENCE s;
DROP TABLE t;
# End of 10.6 tests
30 changes: 30 additions & 0 deletions mysql-test/main/ps_mem_leaks.test
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Expand Up @@ -364,4 +364,34 @@ EXECUTE stmt USING 4;
DEALLOCATE PREPARE stmt;
DROP TABLE t1;

--echo #
--echo # MDEV-39265: Assertion `(mem_root->flags & 4) == 0` failed upon 2nd execution `USING DEFAULT` with sequence
--echo #

CREATE SEQUENCE s;
CREATE TABLE t (a INT DEFAULT(NEXTVAL(s)));
INSERT INTO t VALUES (1), (2);

PREPARE stmt FROM "UPDATE t SET a = ?";

--echo # Verify no SIGABRT
EXECUTE stmt USING 3;
EXECUTE stmt USING DEFAULT;

--echo # Verify the there are no repeated allocations on statement mem_root

SET @saved_dbug = @@SESSION.debug_dbug;
SET SESSION debug_dbug="+d,assert_no_alloc_internal_tables";

EXECUTE stmt USING DEFAULT;
EXECUTE stmt USING 4;
EXECUTE stmt USING DEFAULT;
EXECUTE stmt USING DEFAULT;

SET SESSION debug_dbug= @saved_dbug;

DEALLOCATE PREPARE stmt;
DROP SEQUENCE s;
DROP TABLE t;

--echo # End of 10.6 tests
22 changes: 22 additions & 0 deletions sql/sql_base.cc
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Expand Up @@ -4762,7 +4762,29 @@ add_internal_tables(THD *thd, Query_tables_list *prelocking_ctx,
continue;
}

/*
Debug hook: Verify we only allocate once per internal table.
*/
DBUG_EXECUTE_IF("assert_no_alloc_internal_tables", { DBUG_ASSERT(0); });

/*
When a prepared statement uses DEFAULT (like sequence tables) in its
second or further execution AND if the table is not already on statement's
mem_root, temporarily allow allocating on statement mem_root.
*/
#ifdef PROTECT_STATEMENT_MEMROOT
const bool read_only_mem_root= (thd->mem_root->flags & ROOT_FLAG_READ_ONLY);
if (read_only_mem_root)
thd->mem_root->flags&= ~ROOT_FLAG_READ_ONLY;
#endif

TABLE_LIST *tl= (TABLE_LIST *) thd->alloc(sizeof(TABLE_LIST));

#ifdef PROTECT_STATEMENT_MEMROOT
if (read_only_mem_root)
thd->mem_root->flags|= ROOT_FLAG_READ_ONLY;
#endif

if (!tl)
DBUG_RETURN(TRUE);
tl->init_one_table_for_prelocking(&tables->db,
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