Details
Major Description
PoC:
SELECT * FROM ( SELECT -128 x ) ss GROUP BY x HAVING x = 'x' AND x = ( ( ( x ) IS NULL ) ) ; |
docker log:
mariadbd(my_print_stacktrace+0x32)[0x5645fde287c2]
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mariadbd(handle_fatal_signal+0x488)[0x5645fd901cf8]
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/lib/x86_64-linux-gnu/libc.so.6(+0x42520)[0x7fb7d73c3520]
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mariadbd(_Z21check_simple_equalityP3THDRKN12Value_source7ContextEP4ItemS6_P10COND_EQUAL+0x282)[0x5645fd6ddfc2]
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mariadbd(_Z36and_new_conditions_to_optimized_condP3THDP4ItemPP10COND_EQUALR4ListIS1_EPNS1_11cond_resultE+0x188)[0x5645fd808328]
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mariadbd(_ZN4JOIN14optimize_innerEv+0x152b)[0x5645fd70e9eb]
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mariadbd(_ZN4JOIN8optimizeEv+0xda)[0x5645fd70ee2a]
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mariadbd(_Z12mysql_selectP3THDP10TABLE_LISTR4ListI4ItemEPS4_jP8st_orderS9_S7_S9_yP13select_resultP18st_select_lex_unitP13st_select_lex+0xd1)[0x5645fd70ef21]
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mariadbd(_Z13handle_selectP3THDP3LEXP13select_resulty+0x154)[0x5645fd70f774]
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mariadbd(+0x826f55)[0x5645fd682f55]
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mariadbd(_Z21mysql_execute_commandP3THDb+0x419e)[0x5645fd691f0e]
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mariadbd(_Z11mysql_parseP3THDPcjP12Parser_state+0x1e7)[0x5645fd693237]
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mariadbd(_Z16dispatch_command19enum_server_commandP3THDPcjb+0x14bd)[0x5645fd695a1d]
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mariadbd(_Z10do_commandP3THDb+0x138)[0x5645fd697818]
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mariadbd(_Z24do_handle_one_connectionP7CONNECTb+0x3bf)[0x5645fd7bf3af]
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mariadbd(handle_one_connection+0x5d)[0x5645fd7bf6fd]
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mariadbd(+0xcd1906)[0x5645fdb2d906]
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/lib/x86_64-linux-gnu/libc.so.6(+0x94b43)[0x7fb7d7415b43]
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/lib/x86_64-linux-gnu/libc.so.6(clone+0x44)[0x7fb7d74a6bb4]
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Trying to get some variables.
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Some pointers may be invalid and cause the dump to abort.
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Query (0x7fb7840130d8): SELECT * FROM ( SELECT -128 x ) ss GROUP BY x HAVING x = 'x' AND x = ( ( ( x ) IS NULL ) )
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Connection ID (thread ID): 4
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Status: NOT_KILLED
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Optimizer switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on,table_elimination=on,extended_keys=on,exists_to_in=on,orderby_uses_equalities=on,condition_pushdown_for_derived=on,split_materialized=on,condition_pushdown_for_subquery=on,rowid_filter=on,condition_pushdown_from_having=on,not_null_range_scan=off,hash_join_cardinality=on
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Attachments
Issue Links
- is part of
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MDEV-29363 Constant subquery causing a crash in pushdown optimization
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- Closed
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Activity
The testcase can be shortened to:
CREATE VIEW v1 AS SELECT 1 a; |
SELECT * FROM v1 GROUP BY a HAVING a = 'b' AND a = (a IS NULL); |
With switched off pushdown from HAVING into WHERE optimization the query doesn't crash:
MariaDB [test]> set statement optimizer_switch='condition_pushdown_from_having=off' for |
-> SELECT * FROM v1 GROUP BY a HAVING a = 'b' AND a = (a IS NULL); |
Empty set (0,002 sec) |
The condition that will be pushed into WHERE is looking this way:
v1.a = 'b' and v1.a = (/*always not null*/ 1 is null)
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where /*always not null*/ is v1.a.
In debugger it can be seen that v1.a from (v1.a = 'b') equality and /*always not null*/ are references to the same object.
During the optimization (/*always not null*/ 1 is null) is considered as a constant object and is marked with IMMUTABLE_FL. It will prevent this expression from being fixed and cleaned up on the last stage of the optimization.
When the cleanup process is entered, v1.a from (v1.a = 'b') has IMMUTABLE_FL as it is a reference
to the same object as /*always not null*/. It is not cleaned up or fixed, and IMMUTABLE_FL is removed from this object. Later, when /*always not null*/ is processed, it already doesn't have IMMUTABLE_FL, so it is cleaned up.
Later, when fix fields is made and (/*always not null*/ 1 is null) is processed, no fixing is made on this expression as it has IMMUTABLE_FL. However, /*always not null*/ that was cleaned up on the previous step remains unfixed. That causes a crash.
This bug is similar to MDEV-32304 and will be fixed with MDEV-29363 fix.
Fixed in 10.5. Pushed with MDEV-29363 commit.
The testcase for this MDEV is included in the patch (find it here).
The initial query doesn't crash anymore:
MariaDB [t]> SELECT * FROM ( SELECT -128 x ) ss GROUP BY x HAVING x = 'x' AND x = ( ( ( x ) IS NULL ) ) ; |
Empty set, 1 warning (0,001 sec) |
Thank you for the report!
I repeated on 10.4-11.2:
Version: '10.4.32-MariaDB-debug-log'231009 17:58:37 [ERROR] mysqld got signal 11 ;Server version: 10.4.32-MariaDB-debug-log source revision: 0c7af6a2a19343cb9d4fedbd7165b8f73bc4cf96sql/signal_handler.cc:238(handle_fatal_signal)[0x55c834b6ff8d]sigaction.c:0(__restore_rt)[0x7f03cf269420]sql/sql_select.cc:15122(check_simple_equality(THD*, Value_source::Context const&, Item*, Item*, COND_EQUAL*))[0x55c8344d3f37]sql/opt_subselect.cc:5872(and_new_conditions_to_optimized_cond(THD*, Item*, COND_EQUAL**, List<Item>&, Item::cond_result*))[0x55c8348b58dc]sql/sql_select.cc:2143(JOIN::optimize_inner())[0x55c83446ddec]sql/sql_select.cc:1711(JOIN::optimize())[0x55c83446910d]sql/sql_select.cc:4812(mysql_select(THD*, TABLE_LIST*, unsigned int, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*))[0x55c83448a0f7]sql/sql_select.cc:442(handle_select(THD*, LEX*, select_result*, unsigned long))[0x55c83445ade0]sql/sql_parse.cc:6475(execute_sqlcom_select(THD*, TABLE_LIST*))[0x55c8343c6be4]sql/sql_parse.cc:3978(mysql_execute_command(THD*))[0x55c8343b435b]sql/sql_parse.cc:8012(mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool))[0x55c8343d00bf]sql/sql_parse.cc:1860(dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool))[0x55c8343a64e5]sql/sql_parse.cc:1378(do_command(THD*))[0x55c8343a3010]sql/sql_connect.cc:1420(do_handle_one_connection(CONNECT*))[0x55c8347b0deb]sql/sql_connect.cc:1325(handle_one_connection)[0x55c8347b068f]perfschema/pfs.cc:1871(pfs_spawn_thread)[0x55c83545b274]nptl/pthread_create.c:478(start_thread)[0x7f03cf25d609]Query (0x62b0000a1420): SELECT * FROM ( SELECT 1 x ) ss GROUP BY x HAVING x = 'x' AND x = ( x IS NULL )