mariadb

Tree: 27025221fe

Author	SHA1	Message	Date
Alexey Botchkov	27025221fe	MDEV-9143 JSON_xxx functions. strings/json_lib.c added as a JSON library. SQL frunction added with sql/item_jsonfunc.h/cc	9 years ago
Sergei Golubchik	2ccf247e93	after merge changes: * rename all debugging related command-line options and variables to start from "debug-", and made them all OFF by default. * replace "MySQL" with "MariaDB" in error messages * "Cast ... converted ... integer to it's ... complement" is now a note, not a warning * @@query_cache_strip_comments now has a session scope, not global.	14 years ago
Sergei Golubchik	4d128777dd	revert a suggested "optimization" that introduced a bug compilation error in mysys/my_getsystime.c fixed some redundant code removed sec_to_time, time_to_sec, from_unixtime, unix_timestamp, @@timestamp now use decimal, not double for numbers with a fractional part. purge_master_logs_before_date() fixed many bugs in corner cases fixed mysys/my_getsystime.c: compilation failure fixed sql/sql_parse.cc: don't cut corners. it backfires.	15 years ago
unknown	e0e44ad66e	Bug#30625 (Performance, reduce depth for expressions) This is a performance bug, affecting in particular the bison generated code for the parser. Prior to this fix, the grammar used a long chain of reduces to parse an expression, like: bit_expr -> bit_term bit_term -> bit_factor bit_factor -> value_expr value_expr -> term term -> factor etc This chain of reduces cause the internal state automaton in the generated parser to execute more state transitions and more reduces, so that the generated MySQLParse() function would spend a lot of time looping to execute all the grammar reductions. With this patch, the grammar has been reorganized so that rules are more "flat", limiting the depth of reduces needed to parse <expr>. Tests have been written to enforce that relative priorities and properties of operators have not changed while changing the grammar. See the bug report for performance data. mysql-test/r/parser_precedence.result: Improved test coverage for operator precedence mysql-test/t/parser_precedence.test: Improved test coverage for operator precedence sql/sql_yacc.yy: Simplified the grammar to improve performances	18 years ago
malff/marcsql@weblab.(none)	ec9b9a98aa	Bug#30625 (Performance, reduce depth for expressions) This is a performance bug, affecting in particular the bison generated code for the parser. Prior to this fix, the grammar used a long chain of reduces to parse an expression, like: bit_expr -> bit_term bit_term -> bit_factor bit_factor -> value_expr value_expr -> term term -> factor etc This chain of reduces cause the internal state automaton in the generated parser to execute more state transitions and more reduces, so that the generated MySQLParse() function would spend a lot of time looping to execute all the grammar reductions. With this patch, the grammar has been reorganized so that rules are more "flat", limiting the depth of reduces needed to parse <expr>. Tests have been written to enforce that relative priorities and properties of operators have not changed while changing the grammar. See the bug report for performance data.	18 years ago
unknown	fb1be0f1e5	Bug#30237 (Performance regression in boolean expressions) This is a performance bug, related to the parsing or 'OR' and 'AND' boolean expressions. Let N be the number of expressions involved in a OR (respectively AND). When N=1 For example, "select 1" involve only 1 term: there is no OR operator. In 4.0 and 4.1, parsing expressions not involving OR had no overhead. In 5.0, parsing adds some overhead, with Select->expr_list. With this patch, the overhead introduced in 5.0 has been removed, so that performances for N=1 should be identical to the 4.0 performances, which are optimal (there is no code executed at all) The overhead in 5.0 was in fact affecting significantly some operations. For example, loading 1 Million rows into a table with INSERTs, for a table that has 100 columns, leads to parsing 100 Millions of expressions, which means that the overhead related to Select->expr_list is executed 100 Million times ... Considering that N=1 is by far the most probable expression, this case should be optimal. When N=2 For example, "select a OR b" involves 2 terms in the OR operator. In 4.0 and 4.1, parsing expressions involving 2 terms created 1 Item_cond_or node, which is the expected result. In 5.0, parsing these expression also produced 1 node, but with some extra overhead related to Select->expr_list : creating 1 list in Select->expr_list and another in Item_cond::list is inefficient. With this patch, the overhead introduced in 5.0 has been removed so that performances for N=2 should be identical to the 4.0 performances. Note that the memory allocation uses the new (thd->mem_root) syntax directly. The cost of "is_cond_or" is estimated to be neglectable: the real problem of the performance degradation comes from unneeded memory allocations. When N>=3 For example, "select a OR b OR c ...", which involves 3 or more terms. In 4.0 and 4.1, the parser had no significant cost overhead, but produced an Item tree which is difficult to evaluate / optimize during runtime. In 5.0, the parser produces a better Item tree, using the Item_cond constructor that accepts a list of children directly, but at an extra cost related to Select->expr_list. With this patch, the code is implemented to take the best of the two implementations: - there is no overhead with Select->expr_list - the Item tree generated is optimized and flattened. This is achieved by adding children nodes into the Item tree directly, with Item_cond::add(), which avoids the need for temporary lists and memory allocation Note that this patch also provide an extra optimization, that the previous code in 5.0 did not provide: expressions are flattened in the Item tree, based on what the expression already parsed is, and not based on the order in which rules are reduced. For example : "(a OR b) OR c", "a OR (b OR c)" would both be represented with 2 Item_cond_or nodes before this patch, and with 1 node only with this patch. The logic used is based on the mathematical properties of the OR operator (it's associative), and produces a simpler tree. sql/item_cmpfunc.h: Improved performances for parsing boolean expressions sql/sql_yacc.yy: Improved performances for parsing boolean expressions mysql-test/r/parser_precedence.result: Added test cases to cover boolean operator precedence mysql-test/t/parser_precedence.test: Added test cases to cover boolean operator precedence	18 years ago
malff/marcsql@weblab.(none)	82f99c9359	Bug#30237 (Performance regression in boolean expressions) This is a performance bug, related to the parsing or 'OR' and 'AND' boolean expressions. Let N be the number of expressions involved in a OR (respectively AND). When N=1 For example, "select 1" involve only 1 term: there is no OR operator. In 4.0 and 4.1, parsing expressions not involving OR had no overhead. In 5.0, parsing adds some overhead, with Select->expr_list. With this patch, the overhead introduced in 5.0 has been removed, so that performances for N=1 should be identical to the 4.0 performances, which are optimal (there is no code executed at all) The overhead in 5.0 was in fact affecting significantly some operations. For example, loading 1 Million rows into a table with INSERTs, for a table that has 100 columns, leads to parsing 100 Millions of expressions, which means that the overhead related to Select->expr_list is executed 100 Million times ... Considering that N=1 is by far the most probable expression, this case should be optimal. When N=2 For example, "select a OR b" involves 2 terms in the OR operator. In 4.0 and 4.1, parsing expressions involving 2 terms created 1 Item_cond_or node, which is the expected result. In 5.0, parsing these expression also produced 1 node, but with some extra overhead related to Select->expr_list : creating 1 list in Select->expr_list and another in Item_cond::list is inefficient. With this patch, the overhead introduced in 5.0 has been removed so that performances for N=2 should be identical to the 4.0 performances. Note that the memory allocation uses the new (thd->mem_root) syntax directly. The cost of "is_cond_or" is estimated to be neglectable: the real problem of the performance degradation comes from unneeded memory allocations. When N>=3 For example, "select a OR b OR c ...", which involves 3 or more terms. In 4.0 and 4.1, the parser had no significant cost overhead, but produced an Item tree which is difficult to evaluate / optimize during runtime. In 5.0, the parser produces a better Item tree, using the Item_cond constructor that accepts a list of children directly, but at an extra cost related to Select->expr_list. With this patch, the code is implemented to take the best of the two implementations: - there is no overhead with Select->expr_list - the Item tree generated is optimized and flattened. This is achieved by adding children nodes into the Item tree directly, with Item_cond::add(), which avoids the need for temporary lists and memory allocation Note that this patch also provide an extra optimization, that the previous code in 5.0 did not provide: expressions are flattened in the Item tree, based on what the expression already parsed is, and not based on the order in which rules are reduced. For example : "(a OR b) OR c", "a OR (b OR c)" would both be represented with 2 Item_cond_or nodes before this patch, and with 1 node only with this patch. The logic used is based on the mathematical properties of the OR operator (it's associative), and produces a simpler tree.	18 years ago

5 Commits (27025221fe2ea17aa737ad2ad31011407c00dcc9)