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27d093f68e
Item::shallow_copy() was meant to create a copy of the same class as the item it is called on, but nothing enforced that. A class that does not declare its own override inherits the one of its nearest concrete parent, and get_item_copy<Parent>() then silently creates an object of the parent class, losing the child's virtual behaviour (see MDEV-38801 for an earlier instance with Item_cache_year). Add the ITEM_SHALLOW_COPY(CLASS) macro, which declares the override, and Item::dbug_check_shallow_copy_type(), a debug-only check called from Query_arena::free_items() for every item freed. Once per dynamic type it creates a shallow copy, unlinks it from thd->free_list again (the copy shares pointers with the original and must not be destroyed) and asserts that the copy has the same typeid as the original. The copy is never destroyed: its destructor is not run, and its memory is released when the MEM_ROOT it was allocated on, the current thd->mem_root, is freed. A comment in the check says so. The check found these classes copied as their parent class, now fixed with ITEM_SHALLOW_COPY(): Item_join_operator_plus, Item_null_result, Item_old_field, Item_datetime, Item_empty_string, Item_return_int, Item_trigger_type_of_statement, in_string::Item_string_for_in_vector, Item_is_not_null_test, Item_interval_DDhhmmssff_typecast, Item_string_xml_non_const, Item_func_trt_trx_sees_eq, Item_field_refcursor (type_cursor plugin), Item_field_packable_scalar (type_assoc_array plugin). Item_field_packable_row::shallow_copy() asserted to mark the class as never copied, which the check trips over since it copies every type it meets. It now returns nullptr, the existing way for an item to refuse a copy. No test is added: the check runs under every existing test in a debug build. main and the SQL-layer suites (compat/*, json, funcs_*, vcol, gcol, versioning, period, sys_vars, type_*) pass with it in both normal and --ps-protocol mode. This commit was prepared with Claude Code (Opus 5), which wrote the runtime type check, ran the main and SQL-layer suites in normal and --ps-protocol mode to find the classes that inherited a parent's copy method, added the ITEM_SHALLOW_COPY overrides for them, changed Item_field_packable_row to return nullptr, and documented where the copy made by the check is released.
156 lines
4.3 KiB
C++
156 lines
4.3 KiB
C++
#ifndef ITEM_VERS_INCLUDED
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#define ITEM_VERS_INCLUDED
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/* Copyright (c) 2017, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
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/* System Versioning items */
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class Item_func_history: public Item_bool_func
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{
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public:
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/*
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@param a Item_field for row_end system field
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*/
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Item_func_history(THD *thd, Item *a): Item_bool_func(thd, a)
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{
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DBUG_ASSERT(a->type() == Item::FIELD_ITEM);
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}
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bool val_bool() override;
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bool fix_length_and_dec(THD *thd) override
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{
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set_maybe_null();
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null_value= 0;
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decimals= 0;
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max_length= 1;
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return FALSE;
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}
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LEX_CSTRING func_name_cstring() const override
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{
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static LEX_CSTRING name= {STRING_WITH_LEN("is_history") };
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return name;
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}
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void print(String *str, enum_query_type query_type) override;
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protected:
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Item *shallow_copy(THD *thd) const override
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{ return get_item_copy<Item_func_history>(thd, this); }
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};
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class Item_func_trt_ts: public Item_datetimefunc
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{
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TR_table::field_id_t trt_field;
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public:
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Item_func_trt_ts(THD *thd, Item* a, TR_table::field_id_t _trt_field);
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LEX_CSTRING func_name_cstring() const override
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{
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static LEX_CSTRING begin_name= {STRING_WITH_LEN("trt_begin_ts") };
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static LEX_CSTRING commit_name= {STRING_WITH_LEN("trt_commit_ts") };
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return (trt_field == TR_table::FLD_BEGIN_TS) ? begin_name : commit_name;
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}
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bool get_date(THD *thd, MYSQL_TIME *res, date_mode_t fuzzydate) override;
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bool fix_length_and_dec(THD *thd) override
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{ fix_attributes_datetime(decimals); return FALSE; }
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protected:
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Item *shallow_copy(THD *thd) const override
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{ return get_item_copy<Item_func_trt_ts>(thd, this); }
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};
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class Item_func_trt_id : public Item_longlong_func
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{
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TR_table::field_id_t trt_field;
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bool backwards;
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longlong get_by_trx_id(ulonglong trx_id);
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longlong get_by_commit_ts(MYSQL_TIME &commit_ts, bool backwards);
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public:
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Item_func_trt_id(THD *thd, Item* a, TR_table::field_id_t _trt_field, bool _backwards= false);
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Item_func_trt_id(THD *thd, Item* a, Item* b, TR_table::field_id_t _trt_field);
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LEX_CSTRING func_name_cstring() const override
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{
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static LEX_CSTRING trx_name= {STRING_WITH_LEN("trt_trx_id") };
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static LEX_CSTRING commit_name= {STRING_WITH_LEN("trt_commit_id") };
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static LEX_CSTRING iso_name= {STRING_WITH_LEN("trt_iso_level") };
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switch (trt_field) {
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case TR_table::FLD_TRX_ID:
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return trx_name;
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case TR_table::FLD_COMMIT_ID:
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return commit_name;
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case TR_table::FLD_ISO_LEVEL:
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return iso_name;
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default:
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DBUG_ASSERT(0);
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}
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return NULL_clex_str;
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}
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bool fix_length_and_dec(THD *thd) override
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{
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bool res= Item_int_func::fix_length_and_dec(thd);
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max_length= 20;
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return res;
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}
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longlong val_int() override;
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protected:
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Item *shallow_copy(THD *thd) const override
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{ return get_item_copy<Item_func_trt_id>(thd, this); }
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};
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class Item_func_trt_trx_sees : public Item_bool_func
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{
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protected:
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bool accept_eq;
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public:
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Item_func_trt_trx_sees(THD *thd, Item* a, Item* b);
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LEX_CSTRING func_name_cstring() const override
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{
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static LEX_CSTRING name= {STRING_WITH_LEN("trt_trx_sees") };
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return name;
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}
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bool val_bool() override;
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protected:
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Item *shallow_copy(THD *thd) const override
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{ return get_item_copy<Item_func_trt_trx_sees>(thd, this); }
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};
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class Item_func_trt_trx_sees_eq :
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public Item_func_trt_trx_sees
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{
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public:
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Item_func_trt_trx_sees_eq(THD *thd, Item* a, Item* b) :
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Item_func_trt_trx_sees(thd, a, b)
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{
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accept_eq= true;
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}
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LEX_CSTRING func_name_cstring() const override
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{
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static LEX_CSTRING name= {STRING_WITH_LEN("trt_trx_sees_eq") };
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return name;
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}
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protected:
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ITEM_SHALLOW_COPY(Item_func_trt_trx_sees_eq)
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};
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#endif /* ITEM_VERS_INCLUDED */
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