diff options
Diffstat (limited to 'Docs/internals.texi')
| -rw-r--r-- | Docs/internals.texi | 730 |
1 files changed, 435 insertions, 295 deletions
diff --git a/Docs/internals.texi b/Docs/internals.texi index 2195b42d9a0..871e51c50bd 100644 --- a/Docs/internals.texi +++ b/Docs/internals.texi @@ -1,26 +1,30 @@ \input texinfo @c -*-texinfo-*- -@c Copyright 1998 TcX AB, Detron HB and Monty Program KB +@c Copyright 2002 MySQL AB, TcX AB, Detron HB and Monty Program KB @c @c %**start of header @setfilename internals.info + @c We want the types in the same index -@c @synindex tp fn cp @synindex cp fn + @iftex -@c Well this is normal in Europe. Maybe this should go into the include.texi? @afourpaper @end iftex + @c Get version and other info @include include.texi + @ifclear tex-debug @c This removes the black squares in the right margin @finalout @end ifclear + @c Set background for HTML @set _body_tags BGCOLOR=#FFFFFF TEXT=#000000 LINK=#101090 VLINK=#7030B0 -@settitle @strong{MySQL} internals Manual for version @value{mysql_version}. -@setchapternewpage off +@settitle @strong{MySQL} Internals Manual for version @value{mysql_version}. +@setchapternewpage odd @paragraphindent 0 + @c %**end of header @ifinfo @@ -35,67 +39,78 @@ END-INFO-DIR-ENTRY @sp 10 @center @titlefont{@strong{MySQL} Internals Manual} @sp 10 -@center Copyright @copyright{} 1998 TcX AB, Detron HB and Monty Program KB +@center Copyright @copyright{} 1998-2002 MySQL AB +@page @end titlepage -@node Top, Introduction, (dir), (dir) +@node Top, caching, (dir), (dir) @ifinfo This is a manual about @strong{MySQL} internals. @end ifinfo @menu +* caching:: How MySQL Handles Caching +* flush tables:: How MySQL Handles @code{FLUSH TABLES} +* filesort:: How MySQL Does Sorting (@code{filesort}) +* coding guidelines:: Coding Guidelines +* mysys functions:: Functions In The @code{mysys} Library +* DBUG:: DBUG Tags To Use +* protocol:: MySQL Client/Server Protocol +* Fulltext Search:: Fulltext Search in MySQL @end menu -@node caching,,, -@chapter How MySQL handles caching + +@node caching, flush tables, Top, Top +@chapter How MySQL Handles Caching @strong{MySQL} has the following caches: (Note that the some of the filename have a wrong spelling of cache. :) -@itemize @bullet +@table @strong -@item Key cache +@item Key Cache A shared cache for all B-tree index blocks in the different NISAM files. Uses hashing and reverse linked lists for quick caching of the last used blocks and quick flushing of changed entries for a specific table. (@file{mysys/mf_keycash.c}) -@item Record cache +@item Record Cache This is used for quick scanning of all records in a table. (@file{mysys/mf_iocash.c} and @file{isam/_cash.c}) -@item Table cache +@item Table Cache This holds the last used tables. (@file{sql/sql_base.cc}) -@item Hostname cache +@item Hostname Cache For quick lookup (with reverse name resolving). Is a must when one has a slow DNS. (@file{sql/hostname.cc}) -@item Privilege cache +@item Privilege Cache To allow quick change between databases the last used privileges are cached for each user/database combination. (@file{sql/sql_acl.cc}) -@item Heap table cache -Many use of GROUP BY or DISTINCT caches all found -rows in a HEAP table (this is a very quick in-memory table with hash index) +@item Heap Table Cache +Many use of @code{GROUP BY} or @code{DISTINCT} caches all found rows in +a @code{HEAP} table. (This is a very quick in-memory table with hash index.) -@item Join row cache. -For every full join in a SELECT statement (a full join here means there -were no keys that one could use to find the next table in a list), the -found rows are cached in a join cache. One SELECT query can use many -join caches in the worst case. -@end itemize +@item Join Row Cache +For every full join in a @code{SELECT} statement (a full join here means +there were no keys that one could use to find the next table in a list), +the found rows are cached in a join cache. One @code{SELECT} query can +use many join caches in the worst case. +@end table -@node flush tables,,, -@chapter How MySQL handles flush tables + +@node flush tables, filesort, caching, Top +@chapter How MySQL Handles @code{FLUSH TABLES} @itemize @bullet @item -Flush tables is handled in @code{sql/sql_base.cc::close_cached_tables()}. +Flush tables is handled in @file{sql/sql_base.cc::close_cached_tables()}. @item The idea of flush tables is to force all tables to be closed. This @@ -109,8 +124,8 @@ all tables)! When one does a @code{FLUSH TABLES}, the variable @code{refresh_version} will be incremented. Every time a thread releases a table it checks if the refresh version of the table (updated at open) is the same as -the current refresh_version. If not it will close it and broadcast -a signal on COND_refresh (to wait any thread that is waiting for +the current @code{refresh_version}. If not it will close it and broadcast +a signal on @code{COND_refresh} (to wait any thread that is waiting for all instanses of a table to be closed). @item @@ -119,8 +134,8 @@ The current @code{refresh_version} is also compared to the open refresh version is different the thread will free all locks, reopen the table and try to get the locks again; This is just to quickly get all tables to use the newest version. This is handled by -@code{sql/lock.cc::mysql_lock_tables()} and -@code{sql/sql_base.cc::wait_for_tables()}. +@file{sql/lock.cc::mysql_lock_tables()} and +@file{sql/sql_base.cc::wait_for_tables()}. @item When all tables has been closed @code{FLUSH TABLES} will return an ok @@ -134,8 +149,8 @@ After this it will give other threads a chance to open the same tables. @end itemize -@node Filesort,,, -@chapter How MySQL does sorting (filesort) +@node filesort, coding guidelines, flush tables, Top +@chapter How MySQL Does Sorting (@code{filesort}) @itemize @bullet @@ -146,7 +161,7 @@ Read all rows according to key or by table scanning. Store the sort-key in a buffer (@code{sort_buffer}). @item -When the buffer gets full, run a qsort on it and store the result +When the buffer gets full, run a @code{qsort} on it and store the result in a temporary file. Save a pointer to the sorted block. @item @@ -170,12 +185,13 @@ Now the code in @file{sql/records.cc} will be used to read through them in sorted order by using the row pointers in the result file. To optimize this, we read in a big block of row pointers, sort these and then we read the rows in the sorted order into a row buffer -(@code{record_buffer}) . +(@code{record_buffer}). @end itemize -@node Coding guidelines,,, -@chapter Coding guidelines + +@node coding guidelines, mysys functions, filesort, Top +@chapter Coding Guidelines @itemize @bullet @@ -183,24 +199,28 @@ and then we read the rows in the sorted order into a row buffer We are using @uref{http://www.bitkeeper.com/, BitKeeper} for source management. @item -You should use the @strong{MySQL} 3.23 or 4.0 source for all developments. +You should use the @strong{MySQL} 4.0 source for all developments. @item If you have any questions about the @strong{MySQL} source, you can post these -to @email{developers@@mysql.com} and we will answer them. -Note that we will shortly change the name of this list to -@email{internals@@mysql.com}, to more accurately reflect what should be -posted to this list. +to @email{dev-public@@mysql.com} and we will answer them. Please +remember to not use this internal email list in public! @item -Try to write code in a lot of black boxes that can be reused or at -least have a clean interface. +Try to write code in a lot of black boxes that can be reused or use at +least a clean, easy to change interface. @item Reuse code; There is already a lot of algorithms in MySQL for list handling, queues, dynamic and hashed arrays, sorting, etc. that can be reused. @item +Use the @code{my_*} functions like @code{my_read()}/@code{my_write()}/ +@code{my_malloc()} that you can find in the @code{mysys} library instead +of the direct system calls; This will make your code easier to debug and +more portable. + +@item Try to always write optimized code, so that you don't have to go back and rewrite it a couple of months later. It's better to spend 3 times as much time designing and writing an optimal function than @@ -221,25 +241,23 @@ Don't use two commands on the same line. Do not check the same pointer for @code{NULL} more than once. @item -Use long function and variable names in English; This makes your code -easier to read. Use the 'varible_name' style instead of 'VariableName'. +Use long function and variable names in English. This makes your code +easier to read. @item -Think assembly - make it easier for the compiler to optimize your code. +Use @code{my_var} as opposed to @code{myVar} or @code{MyVar} (@samp{_} +rather than dancing SHIFT to seperate words in identifiers). @item -Comment your code when you do something that someone else may think -is not ''trivial''. +Think assembly - make it easier for the compiler to optimize your code. @item -Use the @code{my_*} functions like @code{my_read()}/@code{my_write()}/ -@code{my_malloc()} that you can find in the @code{mysys} library instead -of the direct system calls; This will make your code easier to debug and -more portable. +Comment your code when you do something that someone else may think +is not ``trivial''. @item -Use @code{libstring} functions instead of standard libc string functions -whenever possible. +Use @code{libstring} functions (in the @file{strings} directory) +instead of standard @code{libc} string functions whenever possible. @item Avoid using @code{malloc()} (its REAL slow); For memory allocations @@ -254,10 +272,6 @@ easily discuss it thoroughly if some other developer thinks there is better way to do the same thing! @item -Use my_var as opposed to myVar or MyVar (@samp{_} rather than dancing SHIFT -to seperate words in identifiers). - -@item Class names start with a capital letter. @item @@ -270,29 +284,28 @@ Any @code{#define}'s are in all-caps. Matching @samp{@{} are in the same column. @item -Put the @samp{@{} after a 'switch' on the same line +Put the @samp{@{} after a @code{switch} on the same line, as this gives +better overall indentation for the switch statement: @example -switch (arg) { +switch (arg) @{ @end example -Because this gives better overall indentation for the switch statement. - @item -In all other cases, @{ and @} should be on their own line, except -if there is nothing inside @{ @}. +In all other cases, @samp{@{} and @samp{@}} should be on their own line, except +if there is nothing inside @samp{@{} and @samp{@}}. @item -Have a space after 'if' +Have a space after @code{if} @item -Put a space after ',' for function arguments +Put a space after @samp{,} for function arguments @item -Functions return 0 on success, and non-zero on error, so you can do: +Functions return @samp{0} on success, and non-zero on error, so you can do: @example -if(a() || b() || c()) { error("something went wrong"); } +if(a() || b() || c()) @{ error("something went wrong"); @} @end example @item @@ -337,113 +350,110 @@ Suggested mode in emacs: (setq c-default-style "MY") @end example -@node mysys functions,,, -@chapter mysys functions - -Functions i mysys: (For flags se my_sys.h) - - int my_copy _A((const char *from,const char *to,myf MyFlags)); - - Copy file - - int my_delete _A((const char *name,myf MyFlags)); - - Delete file - - int my_getwd _A((string buf,uint size,myf MyFlags)); - int my_setwd _A((const char *dir,myf MyFlags)); - - Get and set working directory - - string my_tempnam _A((const char *pfx,myf MyFlags)); - - Make a uniq temp file name by using dir and adding something after - pfx to make name uniq. Name is made by adding a uniq 6 length-string - and TMP_EXT after pfx. - Returns pointer to malloced area for filename. Should be freed by - free(). - - File my_open _A((const char *FileName,int Flags,myf MyFlags)); - File my_create _A((const char *FileName,int CreateFlags, - int AccsesFlags, myf MyFlags)); - int my_close _A((File Filedes,myf MyFlags)); - uint my_read _A((File Filedes,byte *Buffer,uint Count,myf MyFlags)); - uint my_write _A((File Filedes,const byte *Buffer,uint Count, - myf MyFlags)); - ulong my_seek _A((File fd,ulong pos,int whence,myf MyFlags)); - ulong my_tell _A((File fd,myf MyFlags)); - - Use instead of open,open-with-create-flag, close read and write - to get automatic error-messages (flag: MYF_WME) and only have - to test for != 0 if error (flag: MY_NABP). - - int my_rename _A((const char *from,const char *to,myf MyFlags)); - - Rename file - - FILE *my_fopen _A((const char *FileName,int Flags,myf MyFlags)); - FILE *my_fdopen _A((File Filedes,int Flags,myf MyFlags)); - int my_fclose _A((FILE *fd,myf MyFlags)); - uint my_fread _A((FILE *stream,byte *Buffer,uint Count,myf MyFlags)); - uint my_fwrite _A((FILE *stream,const byte *Buffer,uint Count, - myf MyFlags)); - ulong my_fseek _A((FILE *stream,ulong pos,int whence,myf MyFlags)); - ulong my_ftell _A((FILE *stream,myf MyFlags)); - - Same read-interface for streams as for files - - gptr _mymalloc _A((uint uSize,const char *sFile, - uint uLine, myf MyFlag)); - gptr _myrealloc _A((string pPtr,uint uSize,const char *sFile, - uint uLine, myf MyFlag)); - void _myfree _A((gptr pPtr,const char *sFile,uint uLine)); - int _sanity _A((const char *sFile,unsigned int uLine)); - gptr _myget_copy_of_memory _A((const byte *from,uint length, - const char *sFile, uint uLine, - myf MyFlag)); - - malloc(size,myflag) is mapped to this functions if not compiled - with -DSAFEMALLOC - - void TERMINATE _A((void)); - - Writes malloc-info on stdout if compiled with -DSAFEMALLOC. - - int my_chsize _A((File fd,ulong newlength,myf MyFlags)); - - Change size of file - - void my_error _D((int nr,myf MyFlags, ...)); - - Writes message using error number (se mysys/errors.h) on - stdout or curses if MYSYS_PROGRAM_USES_CURSES() is called. - - void my_message _A((const char *str,myf MyFlags)); - - Writes message-string on - stdout or curses if MYSYS_PROGRAM_USES_CURSES() is called. - - void my_init _A((void )); - - Start each program (in main) with this. - void my_end _A((int infoflag)); - - Gives info about program. - - If infoflag & MY_CHECK_ERROR prints if some files are left open - - If infoflag & MY_GIVE_INFO prints timing info and malloc info - about prog. - - int my_redel _A((const char *from, const char *to, int MyFlags)); - - Delete from before rename of to to from. Copyes state from old - file to new file. If MY_COPY_TIME is set sets old time. - - int my_copystat _A((const char *from, const char *to, int MyFlags)); - - Copye state from old file to new file. - If MY_COPY_TIME is set sets copy also time. - - string my_filename _A((File fd)); - - Give filename of open file. - - int dirname _A((string to,const char *name)); - - Copy name of directory from filename. - - int test_if_hard_path _A((const char *dir_name)); - - Test if dirname is a hard path (Starts from root) - - void convert_dirname _A((string name)); - - Convert dirname acording to system. - - In MSDOS changes all caracters to capitals and changes '/' to - '\' - string fn_ext _A((const char *name)); - - Returns pointer to extension in filename - string fn_format _A((string to,const char *name,const char *dsk, - const char *form,int flag)); + +@node mysys functions, DBUG, coding guidelines, Top +@chapter Functions In The @code{mysys} Library + +Functions in @code{mysys}: (For flags see @file{my_sys.h}) + +@table @code +@item int my_copy _A((const char *from, const char *to, myf MyFlags)); +Copy file from @code{from} to @code{to}. + +@item int my_delete _A((const char *name, myf MyFlags)); +Delete file @code{name}. + +@item int my_getwd _A((string buf, uint size, myf MyFlags)); +@item int my_setwd _A((const char *dir, myf MyFlags)); +Get and set working directory. + +@item string my_tempnam _A((const char *pfx, myf MyFlags)); +Make a unique temporary file name by using dir and adding something after +@code{pfx} to make name unique. The file name is made by adding a unique +six character string and @code{TMP_EXT} after @code{pfx}. +Returns pointer to @code{malloc()}'ed area for filename. Should be freed by +@code{free()}. + +@item File my_open _A((const char *FileName,int Flags,myf MyFlags)); +@item File my_create _A((const char *FileName, int CreateFlags, int AccsesFlags, myf MyFlags)); +@item int my_close _A((File Filedes, myf MyFlags)); +@item uint my_read _A((File Filedes, byte *Buffer, uint Count, myf MyFlags)); +@item uint my_write _A((File Filedes, const byte *Buffer, uint Count, myf MyFlags)); +@item ulong my_seek _A((File fd,ulong pos,int whence,myf MyFlags)); +@item ulong my_tell _A((File fd,myf MyFlags)); +Use instead of open, open-with-create-flag, close, read, and write +to get automatic error messages (flag @code{MYF_WME}) and only have +to test for != 0 if error (flag @code{MY_NABP}). + +@item int my_rename _A((const char *from, const char *to, myf MyFlags)); +Rename file from @code{from} to @code{to}. + +@item FILE *my_fopen _A((const char *FileName,int Flags,myf MyFlags)); +@item FILE *my_fdopen _A((File Filedes,int Flags,myf MyFlags)); +@item int my_fclose _A((FILE *fd,myf MyFlags)); +@item uint my_fread _A((FILE *stream,byte *Buffer,uint Count,myf MyFlags)); +@item uint my_fwrite _A((FILE *stream,const byte *Buffer,uint Count, myf MyFlags)); +@item ulong my_fseek _A((FILE *stream,ulong pos,int whence,myf MyFlags)); +@item ulong my_ftell _A((FILE *stream,myf MyFlags)); +Same read-interface for streams as for files. + +@item gptr _mymalloc _A((uint uSize,const char *sFile,uint uLine, myf MyFlag)); +@item gptr _myrealloc _A((string pPtr,uint uSize,const char *sFile,uint uLine, myf MyFlag)); +@item void _myfree _A((gptr pPtr,const char *sFile,uint uLine)); +@item int _sanity _A((const char *sFile,unsigned int uLine)); +@item gptr _myget_copy_of_memory _A((const byte *from,uint length,const char *sFile, uint uLine,myf MyFlag)); +@code{malloc(size,myflag)} is mapped to these functions if not compiled +with @code{-DSAFEMALLOC}. + +@item void TERMINATE _A((void)); +Writes @code{malloc()} info on @code{stdout} if compiled with +@code{-DSAFEMALLOC}. + +@item int my_chsize _A((File fd, ulong newlength, myf MyFlags)); +Change size of file @code{fd} to @code{newlength}. + +@item void my_error _D((int nr, myf MyFlags, ...)); +Writes message using error number (see @file{mysys/errors.h}) on @code{stdout}, +or using curses, if @code{MYSYS_PROGRAM_USES_CURSES()} has been called. + +@item void my_message _A((const char *str, myf MyFlags)); +Writes @code{str} on @code{stdout}, or using curses, if +@code{MYSYS_PROGRAM_USES_CURSES()} has been called. + +@item void my_init _A((void )); +Start each program (in @code{main()}) with this. + +@item void my_end _A((int infoflag)); +Gives info about program. +If @code{infoflag & MY_CHECK_ERROR}, prints if some files are left open. +If @code{infoflag & MY_GIVE_INFO}, prints timing info and malloc info +about program. + +@item int my_redel _A((const char *from, const char *to, int MyFlags)); +Delete @code{from} before rename of @code{to} to @code{from}. Copies state +from old file to new file. If @code{MY_COPY_TIME} is set, sets old time. + +@item int my_copystat _A((const char *from, const char *to, int MyFlags)); +Copy state from old file to new file. If @code{MY_COPY_TIME} is set, +sets old time. + +@item string my_filename _A((File fd)); +Returns filename of open file. + +@item int dirname _A((string to, const char *name)); +Copy name of directory from filename. + +@item int test_if_hard_path _A((const char *dir_name)); +Test if @code{dir_name} is a hard path (starts from root). + +@item void convert_dirname _A((string name)); +Convert dirname according to system. +In MSDOS, changes all characters to capitals and changes @samp{/} to @samp{\}. + +@item string fn_ext _A((const char *name)); +Returns pointer to extension in filename. + +@item string fn_format _A((string to,const char *name,const char *dsk,const char *form,int flag)); format a filename with replace of library and extension and converts between different systems. params to and name may be identicall @@ -457,117 +467,204 @@ Functions i mysys: (For flags se my_sys.h) "open(fn_format(temp_buffe,name,"","",4),...)" to unpack home and convert filename to system-form. - string fn_same _A((string toname,const char *name,int flag)); - - Copys directory and extension from name to toname if neaded. - copy can be forced by same flags that in fn_format. +@item string fn_same _A((string toname, const char *name, int flag)); +Copys directory and extension from @code{name} to @code{toname} if neaded. +Copying can be forced by same flags used in @code{fn_format()}. + +@item int wild_compare _A((const char *str, const char *wildstr)); +Compare if @code{str} matches @code{wildstr}. @code{wildstr} can contain +@samp{*} and @samp{?} as wildcard characters. +Returns 0 if @code{str} and @code{wildstr} match. + +@item void get_date _A((string to, int timeflag)); +Get current date in a form ready for printing. + +@item void soundex _A((string out_pntr, string in_pntr)) +Makes @code{in_pntr} to a 5 char long string. All words that sound +alike have the same string. + +@item int init_key_cache _A((ulong use_mem, ulong leave_this_much_mem)); +Use caching of keys in MISAM, PISAM, and ISAM. +@code{KEY_CACHE_SIZE} is a good size. +Remember to lock databases for optimal caching. + +@item void end_key_cache _A((void)); +End key caching. +@end table + - int wild_compare _A((const char *str,const char *wildstr)); - - Compare if str matches wildstr. Wildstr can contain "*" and "?" - as match-characters. - Returns 0 if match. - void get_date _A((string to,int timeflag)); - - Get current date in a form ready for printing. +@node DBUG, protocol, mysys functions, Top +@chapter DBUG Tags To Use - void soundex _A((string out_pntr, string in_pntr)) - - Makes in_pntr to a 5 chars long string. All words that sounds - alike have the same string. +Here is some of the tags we now use: +(We should probably add a couple of new ones) - int init_key_cache _A((ulong use_mem,ulong leave_this_much_mem)); - - Use cacheing of keys in MISAM, PISAM, and ISAM. - KEY_CACHE_SIZE is a good size. - - Remember to lock databases for optimal cacheing +@table @code +@item enter +Arguments to the function. - void end_key_cache _A((void)); - - End key-cacheing. +@item exit +Results from the function. -@node protocol,,, -@chapter MySQL client/server protocol +@item info +Something that may be interesting. -Raw packet without compression -============================== -------------------------------------------------- -| Packet Length | Packet no | Data | -| 3 Bytes | 1 Byte | n Bytes | -------------------------------------------------- +@item warning +When something doesn't go the usual route or may be wrong. -3 Byte packet length - The length is calculated with int3store - See include/global.h for details. - The max packetsize can be 16 MB. -1 Byte packet no +@item error +When something went wrong. -If no compression is used the first 4 bytes of each paket -is the header of the paket. -The packet number is incremented for each sent packet. The first -packet starts with 0 +@item loop +Write in a loop, that is probably only useful when debugging +the loop. These should normally be deleted when one is +satisfied with the code and it has been in real use for a while. +@end table -n Byte data +Some specific to mysqld, because we want to watch these carefully: + +@table @code +@item trans +Starting/stopping transactions. + +@item quit +@code{info} when mysqld is preparing to die. + +@item query +Print query. +@end table + + +@node protocol, Fulltext Search, DBUG, Top +@chapter MySQL Client/Server Protocol + +@menu +* raw packet without compression:: +* raw packet with compression:: +* basic packets:: +* communication:: +* fieldtype codes:: +@end menu + +@node raw packet without compression, raw packet with compression, protocol, protocol +@section Raw Packet Without Compression + +@example ++-----------------------------------------------+ +| Packet Length | Packet no | Data | +| 3 Bytes | 1 Byte | n Bytes | ++-----------------------------------------------+ +@end example + +@table @asis +@item 3 Byte packet length +The length is calculated with int3store +See include/global.h for details. +The max packetsize can be 16 MB. + +@item 1 Byte packet no +If no compression is used the first 4 bytes of each packet is the header +of the packet. The packet number is incremented for each sent packet. +The first packet starts with 0. +@item n Byte data + +@end table The packet length can be recalculated with: + +@example length = byte1 + (256 * byte2) + (256 * 256 * byte3) - -Raw packet with compression -=========================== ------------------------------------------------------ -| Packet Length | Packet no | Uncomp. Packet Length | -| 3 Bytes | 1 Byte | 3 Bytes | ------------------------------------------------------ - -3 Byte packet length - The length is calculated with int3store - See include/global.h for details. - The max packetsize can be 16 MB. -1 Byte packet no -3 Byte uncompressed packet length - -If compression is used the first 7 bytes of each paket -is the header of the paket. - -Basic packets -============== -OK-packet - For details see sql/net_pkg.cc - function send_ok - ------------------------------------------------- - | Header | No of Rows | Affected Rows | - | | 1 Byte | 1-8 Byte | - ------------------------------------------------- - | ID (last_insert_id) | Status | Length | - | 1-8 Byte | 2 Byte | 1-8 Byte | - ------------------------------------------------- - | Messagetext | - | n Byte | - ------------------------------------------------- - - Header - 1 byte number of rows ? (always 0 ?) - 1-8 bytes affected rows - 1-8 byte id (last_insert_id) - 2 byte Status (usually 0) - If the OK-packege includes a message: - 1-8 bytes length of message - n bytes messagetext - -Error-packet - ------------------------------------------------- - | Header | Statuscode | Error no | - | | 1 Byte | 2 Byte | - ------------------------------------------------- - | Messagetext | 0x00 | - | n Byte | 1 Byte | - ------------------------------------------------- - - Header - 1 byte status code (0xFF = ERROR) - 2 byte error number (is only sent to new 3.23 clients. - n byte errortext - 1 byte 0x00 - - - -The communication -================= +@end example + + +@node raw packet with compression, basic packets, raw packet without compression, protocol +@section Raw Packet With Compression + +@example ++---------------------------------------------------+ +| Packet Length | Packet no | Uncomp. Packet Length | +| 3 Bytes | 1 Byte | 3 Bytes | ++---------------------------------------------------+ +@end example + +@table @asis +@item 3 Byte packet length +The length is calculated with int3store +See include/global.h for details. +The max packetsize can be 16 MB. + +@item 1 Byte packet no +@item 3 Byte uncompressed packet length +@end table + +If compression is used the first 7 bytes of each packet +is the header of the packet. + + +@node basic packets, communication, raw packet with compression, protocol +@section Basic Packets + +@menu +* ok packet:: +* error packet:: +@end menu + + +@node ok packet, error packet, basic packets, basic packets +@subsection OK Packet + +For details, see @file{sql/net_pkg.cc::send_ok()}. + +@example ++-----------------------------------------------+ +| Header | No of Rows | Affected Rows | +| | 1 Byte | 1-8 Byte | +|-----------------------------------------------| +| ID (last_insert_id) | Status | Length | +| 1-8 Byte | 2 Byte | 1-8 Byte | +|-----------------------------------------------| +| Messagetext | +| n Byte | ++-----------------------------------------------+ +@end example + +@table @asis +@item Header +@item 1 byte number of rows ? (always 0 ?) +@item 1-8 bytes affected rows +@item 1-8 byte id (last_insert_id) +@item 2 byte Status (usually 0) +@item If the OK-packege includes a message: +@item 1-8 bytes length of message +@item n bytes messagetext +@end table + + +@node error packet, , ok packet, basic packets +@subsection Error Packet + +@example ++-----------------------------------------------+ +| Header | Status code | Error no | +| | 1 Byte | 2 Byte | +|-----------------------------------------------| +| Messagetext | 0x00 | +| n Byte | 1 Byte | ++-----------------------------------------------+ +@end example + +@table @asis +@item Header +@item 1 byte status code (0xFF = ERROR) +@item 2 byte error number (is only sent to new 3.23 clients. +@item n byte errortext +@item 1 byte 0x00 +@end table + + +@node communication, fieldtype codes, basic packets, protocol +@section Communication > Packet from server to client < Paket from client tor server @@ -658,28 +755,29 @@ The communication n data -Fieldtype Codes: -================ - - display_length |enum_field_type |flags - ---------------------------------------------------- -Blob 03 FF FF 00 |01 FC |03 90 00 00 -Mediumblob 03 FF FF FF |01 FC |03 90 00 00 -Tinyblob 03 FF 00 00 |01 FC |03 90 00 00 -Text 03 FF FF 00 |01 FC |03 10 00 00 -Mediumtext 03 FF FF FF |01 FC |03 10 00 00 -Tinytext 03 FF 00 00 |01 FC |03 10 00 00 -Integer 03 0B 00 00 |01 03 |03 03 42 00 -Mediumint 03 09 00 00 |01 09 |03 00 00 00 -Smallint 03 06 00 00 |01 02 |03 00 00 00 -Tinyint 03 04 00 00 |01 01 |03 00 00 00 -Varchar 03 XX 00 00 |01 FD |03 00 00 00 -Enum 03 05 00 00 |01 FE |03 00 01 00 -Datetime 03 13 00 00 |01 0C |03 00 00 00 -Timestamp 03 0E 00 00 |01 07 |03 61 04 00 -Time 03 08 00 00 |01 0B |03 00 00 00 -Date 03 0A 00 00 |01 0A |03 00 00 00 +@node fieldtype codes, , communication, protocol +@section Fieldtype Codes +@example + display_length |enum_field_type |flags + ---------------------------------------------------- +Blob 03 FF FF 00 |01 FC |03 90 00 00 +Mediumblob 03 FF FF FF |01 FC |03 90 00 00 +Tinyblob 03 FF 00 00 |01 FC |03 90 00 00 +Text 03 FF FF 00 |01 FC |03 10 00 00 +Mediumtext 03 FF FF FF |01 FC |03 10 00 00 +Tinytext 03 FF 00 00 |01 FC |03 10 00 00 +Integer 03 0B 00 00 |01 03 |03 03 42 00 +Mediumint 03 09 00 00 |01 09 |03 00 00 00 +Smallint 03 06 00 00 |01 02 |03 00 00 00 +Tinyint 03 04 00 00 |01 01 |03 00 00 00 +Varchar 03 XX 00 00 |01 FD |03 00 00 00 +Enum 03 05 00 00 |01 FE |03 00 01 00 +Datetime 03 13 00 00 |01 0C |03 00 00 00 +Timestamp 03 0E 00 00 |01 07 |03 61 04 00 +Time 03 08 00 00 |01 0B |03 00 00 00 +Date 03 0A 00 00 |01 0A |03 00 00 00 +@end example @c The Index was empty, and ugly, so I removed it. (jcole, Sep 7, 2000) @@ -688,6 +786,48 @@ Date 03 0A 00 00 |01 0A |03 00 00 00 @c @printindex fn +@node Fulltext Search, , protocol, Top +@chapter Fulltext Search in MySQL + +Hopefully, sometime there will be complete description of +fulltext search algorithms. +Now it's just unsorted notes. + +@menu +* Weighting in boolean mode:: +@end menu + +@node Weighting in boolean mode, , , Fulltext Search +@section Weighting in boolean mode + +The basic idea is as follows: in expression +@code{A or B or (C and D and E)}, either @code{A} or @code{B} alone +is enough to match the whole expression. While @code{C}, +@code{D}, and @code{E} should @strong{all} match. So it's +reasonable to assign weight 1 to @code{A}, @code{B}, and +@code{(C and D and E)}. And @code{C}, @code{D}, and @code{E} +should get a weight of 1/3. + +Things become more complicated when considering boolean +operators, as used in MySQL FTB. Obvioulsy, @code{+A +B} +should be treated as @code{A and B}, and @code{A B} - +as @code{A or B}. The problem is, that @code{+A B} can @strong{not} +be rewritten in and/or terms (that's the reason why this - extended - +set of operators was chosen). Still, aproximations can be used. +@code{+A B C} can be approximated as @code{A or (A and (B or C))} +or as @code{A or (A and B) or (A and C) or (A and B and C)}. +Applying the above logic (and omitting mathematical +transformations and normalization) one gets that for +@code{+A_1 +A_2 ... +A_N B_1 B_2 ... B_M} the weights +should be: @code{A_i = 1/N}, @code{B_j=1} if @code{N==0}, and, +otherwise, in the first rewritting approach @code{B_j = 1/3}, +and in the second one - @code{B_j = (1+(M-1)*2^M)/(M*(2^(M+1)-1))}. + +The second expression gives somewhat steeper increase in total +weight as number of matched B's increases, because it assigns +higher weights to individual B's. Also the first expression in +much simplier. So it is the first one, that is implemented in MySQL. + @summarycontents @contents |