multiquery packet).
Background:
- a query can contain multiple SQL statements;
- the server frees resources allocated to process a query when the
whole query is handled. In other words, resources allocated to process
one SQL statement from a multi-statement query are freed when all SQL
statements are handled.
The problem was that the parser allocated a buffer of size of the whole
query for each SQL statement in a multi-statement query. Thus, if a query
had many SQL-statements (so, the query was long), but each SQL statement
was short, ther parser tried to allocate huge amount of memory (number of
small SQL statements * length of the whole query).
The memory was allocated for a so-called "cpp buffer", which is intended to
store pre-processed SQL statement -- SQL text without version specific
comments.
The fix is to allocate memory for the "cpp buffer" once for all SQL
statements (once for a query).
build)
The crash was caused by freeing the internal parser stack during the parser
execution.
This occured only for complex stored procedures, after reallocating the parser
stack using my_yyoverflow(), with the following C call stack:
- MYSQLparse()
- any rule calling sp_head::restore_lex()
- lex_end()
- x_free(lex->yacc_yyss), xfree(lex->yacc_yyvs)
The root cause is the implementation of stored procedures, which breaks the
assumption from 4.1 that there is only one LEX structure per parser call.
The solution is to separate the LEX structure into:
- attributes that represent a statement (the current LEX structure),
- attributes that relate to the syntax parser itself (Yacc_state),
so that parsing multiple statements in stored programs can create multiple
LEX structures while not changing the unique Yacc_state.
Now, Yacc_state and the existing Lex_input_stream are aggregated into
Parser_state, a structure that represent the complete state of the (Lexical +
Syntax) parser.
mysql-test/r/parser_stack.result:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
mysql-test/t/parser_stack.test:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sp.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sp_head.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_class.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_class.h:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_lex.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_lex.h:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_parse.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_prepare.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_trigger.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_view.cc:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
sql/sql_yacc.yy:
Bug#35577 (CREATE PROCEDURE causes either crash or syntax error depending on
build)
