diff options
Diffstat (limited to 'Docs')
| -rw-r--r-- | Docs/.cvsignore | 37 | ||||
| -rw-r--r-- | Docs/linuxthreads.txt | 2 | ||||
| -rw-r--r-- | Docs/my_sys.txt | 140 | ||||
| -rw-r--r-- | Docs/net_doc.txt | 943 |
4 files changed, 3 insertions, 1119 deletions
diff --git a/Docs/.cvsignore b/Docs/.cvsignore index 777efb1eb7b..6a00212535b 100644 --- a/Docs/.cvsignore +++ b/Docs/.cvsignore @@ -1,40 +1,5 @@ -COPYING -COPYING.LIB +INSTALL-SOURCE INSTALL-BINARY Makefile Makefile.in -Manual-updates -before-gpl-changes-manual.texi -include.texi -manual-before-gpl.texi -manual-tmp.aux -manual-tmp.cp -manual-tmp.fn -manual-tmp.ky -manual-tmp.log -manual-tmp.pdf -manual-tmp.pg -manual-tmp.texi -manual-tmp.toc -manual-tmp.tp -manual-tmp.vr -manual.aux -manual.cp -manual.cps -manual.fn -manual.fns -manual.html -manual.ky -manual.log -manual.pdf -manual.pg -manual.toc -manual.tp -manual.txt -manual.vr -manual_a4.ps -manual_a4.ps.gz -manual_letter.ps -manual_letter.ps.gz -manual_toc.html mysql.info diff --git a/Docs/linuxthreads.txt b/Docs/linuxthreads.txt index 30270125c0d..552415fe794 100644 --- a/Docs/linuxthreads.txt +++ b/Docs/linuxthreads.txt @@ -1,3 +1,5 @@ +[Note this information is obsolete] + Notes on compiling glibc for the standard MySQL binary: - make sure you have gcc 2.95 and gmake 3.79 or newer diff --git a/Docs/my_sys.txt b/Docs/my_sys.txt deleted file mode 100644 index 85ffc13ecb4..00000000000 --- a/Docs/my_sys.txt +++ /dev/null @@ -1,140 +0,0 @@ -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)); - format a filename with replace of library and extension and - converts between different systems. - params to and name may be identicall - function dosn't change name if name != to - Flag may be: 1 force replace filnames library with 'dsk' - 2 force replace extension with 'form' */ - 4 force Unpack filename (replace ~ with home) - 8 Pack filename as short as possibly for output to - user. - All open requests should allways use at least: - "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. - - 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. - - 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. - - 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 - - void end_key_cache _A((void)); - - End key-cacheing. diff --git a/Docs/net_doc.txt b/Docs/net_doc.txt deleted file mode 100644 index 4f21383c06d..00000000000 --- a/Docs/net_doc.txt +++ /dev/null @@ -1,943 +0,0 @@ - MySQL Client/Server Protocol Documentation - - - -Introduction ------------- - - -This paper has the objective of presenting a through description -of the client/server protocol that is embodied in MySQL. Particularly, -this paper aims to document and describe: - -- manner in which MySQL server detects client connection requests and - creates connection -- manner in which MySQL client C API call connects to server - the - entire protocol of sending/receiving data by MySQL server and C API - code -- manner in which queries are sent by client C API calls to server -- manner in which query results are sent by server -- manner in which query results are resolved by server -- sending and receiving of error messages - - -This paper does not have the goal or describing nor documenting other -related MySQL issues, like usage of thread libraries, MySQL standard -library set, MySQL strings library and other MySQL specific libraries, -type definitions and utilities. - -Issues that are covered by this paper are contained in the following -source code files: - -- libmysql/net.c and sql/net_serv.cc, the two being identical -- client/libmysql.c (not entire file is covered) -- include/mysql_com.h -- include/mysql.h -- sql/mysqld.cc (not entire file is covered) -- sql/net_pkg.cc -- sql/sql_base.cc (not entire file is covered) -- sql/sql_select.cc (not entire file is covered) -- sql/sql_parse.cc (not entire file is covered) - -Note: libmysql/net.c was client/net.c prior to MySQL 3.23.11. -sql/net_serv.cc was sql/net_serv.c prior to MySQL 3.23.16. - -Beside this introduction this paper presents basic definitions, -constants, structures and global variables, all related functions in -server and in C API. Textual description of the entire protocol -functioning is described in the last chapter of this paper. - - -Constants, structures and global variables ------------------------------------------- - -This chapter will describe all constants, structures and -global variables relevant to client/server protocol. - -Constants - -They are important as they contain default values, the ones -that are valid if options are not set in any other way. Beside that -MySQL source code does not contain a single non-defined constant in -its code. This description of constants does not include -configuration and conditional compilation #defines. - -NAME_LEN - field and table name length, current value 64 -HOSTNAME_LENGTH - length of the hostname, current value 64 -USERNAME_LENGTH - username length, current value 16 -MYSQL_PORT - default TCP/IP port number, current value 3306 -MYSQL_UNIX_ADDR - full path of the default Unix socket file, current value - "/tmp/mysql.sock" -MYSQL_NAMEDPIPE - full path of the default NT pipe file, current value - "MySQL" -MYSQL_SERVICENAME - name of the MySQL Service on NT, current value "MySQL" -NET_HEADER_SIZE - size of the network header, when no - compression is used, current value 4 -COMP_HEADER_SIZE - additional size of network header when - compression is used, current value 3 - -What follows are set of constants, defined in source only, which -define capabilities of the client built with that version of C -API. Simply, when some new feature is added in client, that client -feature is defined, so that server can detect what capabilities a -client program has. - -CLIENT_LONG_PASSWORD - client supports new more secure passwords -CLIENT_LONG_FLAG - client uses longer flags -CLIENT_CONNECT_WITH_DB - client can specify db on connect -CLIENT_COMPRESS - client can use compression protocol -CLIENT_ODBC - ODBC client -CLIENT_LOCAL_FILES - client can use LOAD DATA INFILE LOCAL -CLIENT_IGNORE_SPACE - client can ignore spaces before '(' -CLIENT_CHANGE_USER - client supports the mysql_change_user() - -What follows are other constants, pertaining to timeouts and sizes - -MYSQL_ERRMSG_SIZE - maximum size of error message string, current value 200 -NET_READ_TIMEOUT - read timeout, current value 30 seconds -NET_WRITE_TIMEOUT - write timeout, current value 60 seconds -NET_WAIT_TIMEOUT - wait for new query timeout, current value 8*60*60 - seconds, that is, 8 hours -packet_error - value returned in case of socket errors, current - value -1 -TES_BLOCKING - used in debug mode for setting up blocking testing -RETRY COUNT - number of times network read and write will be - retried, current value 1 - -There are also error messages for last_errno, which depict system -errors, and are used on the server only. - -ER_NET_PACKAGE_TOO_LARGE - packet is larger than max_allowed_packet -ER_OUT_OF_RESOURCES - practically no more memory -ER_NET_ERROR_ON_WRITE - error in writing to NT Named Pipe -ER_NET_WRITE_INTERRUPTED - some signal or interrupt happened - during write -ER_NET_READ_ERROR_FROM_PIPE - error in reading from NT Named Pipe -ER_NET_FCNTL_ERROR - error in trying to set fcntl on socket - descriptor -ER_NET_PACKETS_OUT_OF_ORDER - packet numbers on client and - server side differ -ER_NET_UNCOMPRESS_ERROR - error in uncompress of compressed packet - - - Structs and enums - - -struct NET - -This is MySQL's network handle structure, used in all client/server -read/write functions. On the server, it is initialized and preserved -in each thread. On the client, it is a part of the MYSQL struct, -which is the MySQL handle used in all C API functions. This structure -uniquely identifies a connection, either on the server or client -side. It consists of the following fields: - - Vio* vio - explained above - HANDLE hPipe - Handle for NT Named Pipe file - my_socket fd - file descriptor used for both TCP/IP socket and - Unix socket file - int fcntl - contains info on fcntl options used on fd. Mostly - used for saving info if blocking is used or not - unsigned char *buff - network buffer used for storing data for - reading from/writing to socket - unsigned char,*buff_end - points to the end of buff - unsigned char *write_pos - present writing position in buff - unsigned char *read_pos - present reading position in buff. This - pointer is used for reading data after - calling my_net_read function and function - that are just its wrappers - char last_error[MYSQL_ERRMSG_SIZE] - holds last error message - unsigned int last_errno - holds last error code of the network - protocol. Its possible values are listed - in above constants. It is used only on - the server side - unsigned int max_packet - holds current value of buff size - unsigned int timeout - stores read timeout value for that connection - unsigned int pkt_nr - stores the value of the current packet number in - a batch of packets. Used primarily for - detection of protocol errors resulting in a - mismatch - my_bool error - holds either 1 or 0 depending on the error condition - my_bool return_errno - if its value != 0 then there is an error in - protocol mismatch between client and server - my_bool compress - if true compression is used in the protocol - unsigned long remain_in_buf - used only in reading compressed packets. - Explained in my_net_read - unsigned long length - used only for storing the length of the read - packet. Explained in my_net_read - unsigned long buf_length - used only in reading compressed packets. - Explained in my_net_read - unsigned long where_b - used only in reading compressed packets. - Explained in my_net_read - short int more - used for reporting in mysql_list_processes - char save_char - used in reading compressed packets for saving chars - in order to make zero-delimited strings. Explained - in my_net_read - -A few typedefs will be defined for easier understanding of the text that -follows. - -typedef char **MYSQL_ROW - data containing one row of values - -typedef unsigned int MYSQL_FIELD_OFFSET - offset in bytes of the current field - -typedef MYSQL_ROWS *MYSQL_ROW_OFFSET - offset in bytes of the current row - -struct MYSQL_FIELD - contains all info on the attributes of a -specific column in a result set, plus info on lengths of the column in -a result set. This struct is tagged as st_mysql_field. This structure -consists of the following fields: - - char *name - name of column - char *table - table of column if column was a field and not - an expression or constant - char *def - default value (set by mysql_list_fields) - enum enum_field_types type - see above - unsigned int length - width of column in the current row - unsigned int max_length - maximum width of that column in entire - result set - unsigned int flags - corresponding to Extra in DESCRIBE - unsigned int decimals - number of decimals in field - - -struct MYSQL_ROWS - a node for each row in the single linked -list forming entire result set. This struct is tagged as -st_mysql_rows, and has two fields: - - struct st_mysql_rows *next - pointer to the next one - MYSQL_ROW data - see above - - -struct MYSQL_DATA - contains all rows from result set. It is -tagged as st_mysql_data and has following fields: - - my_ulonglong rows - how many rows - unsigned int fields - how many columns - MYSQL_ROWS *data - see above. This is the first node of the linked list - MEM_ROOT alloc - MEM_ROOT is MySQL memory allocation structure, and - this field is used to store all fields and rows. - - -struct st_mysql_options - holds various client options, and -contains following fields: - - unsigned int connect_timeout - time in seconds for connection - unsigned int client_flag - used to hold client capabilities - my_bool compress - boolean for compression - my_bool named_pipe - is Named Pipe used? (on NT) - unsigned int port - what TCP port is used - char *host - host to connect to - char *init_command - command to be executed upon connection - char *user - account name on MySQL server - char *password - password for the above - char *unix_socket - full path for Unix socket file - char *db - default database - char *my_cnf_file - optional configuration file - char *my_cnf_group - optional header for options - - -struct MYSQL - MySQL client's handle. Required for any -operation issued from client to server. Tagged as st_mysql and having -following fields: - - NET net - see above - char *host - host on which MySQL server is running - char *user - MySQL username - char *passwd - password for above - char *unix_socket- full path of Unix socket file - char *server_version - version of the server - char *host_info - contains info on how has connection been - established, TCP port, socket or Named Pipe - char *info - used to store information on the query results, - like number of rows affected etc. - char *db - current database - unsigned int port - TCP port in use - unsigned int client_flag - client capabilities - unsigned int server_capabilities - server capabilities - unsigned int protocol_version - version of the protocol - unsigned int field_count - used for storing number of fields - immediately upon execution of a query, - but before fetching rows - unsigned long thread_id - server thread to which this connection - is attached - my_ulonglong affected_rows - used for storing number of rows - immediately upon execution of a query, - but before fetching rows - my_ulonglong insert_id - fetching LAST_INSERT_ID() through client C API - my_ulonglong extra_info - used by mysqlshow -unsigned long packet_length - saving size of the first packet upon - execution of a query - enum mysql_status status - see above - MYSQL_FIELD *fields - see above - MEM_ROOT field_alloc - memory used for storing previous field (fields) - my_bool free_me - boolean that flags if MYSQL was allocated in mysql_init - my_bool reconnect - used to automatically reconnect - struct st_mysql_options options - see above - char scramble_buff[9] - key for scrambling password before sending it - to server - - -struct MYSQL_RES - tagged as st_mysql_res and used to store -entire result set from a single query. Contains following fields: - - my_ulonglong row_count - number of rows - unsigned int field_count - number of columns - unsigned int current_field - cursor for fetching fields - MYSQL_FIELD *fields - see above - MYSQL_DATA *data - see above, and used in buffered reads, that is, - mysql_store_result only - MYSQL_ROWS *data_cursor - pointing to the field of above "data" - MEM_ROOT field_alloc - memory allocation for above "fields" - MYSQL_ROW row - used for storing row by row in unbuffered reads, - that is, in mysql_use_result - MYSQL_ROW current_row - cursor to the current row for buffered reads - unsigned long *lengths - column lengths of current row - MYSQL *handle - see above, used in unbuffered reads, that is, in - mysql_use_result - my_bool eof - used by mysql_fetch_row as a marker for end of data - - - - Global variables - - -unsigned long max_allowed_packet - maximum allowable value of network - buffer. Default value - 1MB - -unsigned long net_buffer_length - default, starting value of network - buffer - 8KB - -unsigned long bytes_sent - total number of bytes written since startup - of the server - -unsigned long bytes_received - total number of bytes read since startup - of the server - - -Synopsis of the basic client/server protocol --------------------------------------------- - -Purpose of this chapter is to provide a complete picture of -the basic client/server protocol implemented in MySQL. It was felt -it is necessary after writing descriptions for all of the functions -involved in basic protocol. There are at present 11 functions -involved, with several structures, many constants etc, which are all -described in detail. But as a forest could not be seen from the trees, -so the concept of the protocol could not be deciphered easily from a -thorough documentation of minutiae. - -Although the concept of the protocol was not changed with the -introduction of vio system, embodied in violate.cc source file and VIO -system, the introduction of these has changed the code substantially. Before -VIO was introduced, functions for reading from/writing to network -connection had to deal with various network standards. So, these functions -depended on whether TCP port or Unix socket file or NT Named Pipe file is -used. This is all changed now and single vio_ functions are called, while -all this diversity is covered by vio_ functions. - -In MySQL a specific buffered network input/output transport model -has been implemented. Although each operating system may have its -own buffering for network connections, MySQL has added its own -buffering model. This same for each of the three transport protocol -types that are used in MySQL client/server communications, which -are TCP/IP sockets (on all systems), Unix socket files on Unix and -Unix-like operating systems and Named Pipe files on NT. Although -TCP/IP sockets are omnipresent, the latter two types have been added -for local connections. Those two connection types can be used in -local mode only, that is, when both client and server reside on the -same host, and are introduced because they enable better speeds for -local connections. This is especially useful for WWW type of -applications. Startup options of MySQL server allow that either -TCP/IP sockets or local connection (OS dependent) can be disallowed. - -In order to implement buffered input/output, MySQL allocates a -buffer. The starting size of this buffer is determined by the value -of the global variable net_buffer_length, which can be changed at -MySQL server startup. This is, as explained, only the startup length -of MySQL network buffer. Because a single item that has to be read -or written can be larger than that value, MySQL will increase buffer -size as long as that size reaches value of the global variable -max_allowed_packet, which is also settable at server startup. Maximum -value of this variable is limited by the way MySQL stores/reads -sizes of packets to be sent/read, which means by the way MySQL -formats packages. - -Basically each packet consists of two parts, a header and data. In -the case when compression is not used, header consists of 4 bytes -of which 3 contain the length of the packet to be sent and one holds -the packet number. When compression is used there are onother 3 -bytes which store the size of uncompressed data. Because of the way -MySQL packs length into 3 bytes, plus due to the usage of some -special values in the most significant byte, maximum size of -max_allowed_packet is limited to 24MB at present. So, if compression -is not used, at first 4 bytes are written to the buffer and then -data itself. As MySQL buffers I/O logical packets are packet together -until packets fill up entire size of the buffer. That size no less -than net_buffer_size, but no greater than max_allowed_packet. So, -actual writing to the network is done when this buffer is filled -up. As frequently sequence of buffers make a logical unit, like a -result set, then at the end of sending data, even if buffer is not -full, data is written (flushed to the connection) with a call of -the net_flush function. So that no single packet can be larger than -this value, checks are made throughout the code to make sure that -no single field or command could exceed that value. - -In order to maintain coherency in consecutive packets, each packet -is numbered and their number stored as a part of a header, as -explained above. Packets start with 0, so whenever a logical packet -is written, that number is incremented. On the other side when -packets are read, value that is fetched is compared with the value -stored and if there is no mismatch that value is incremented, too. -Packet number is reset on the client side when unwanted connections -are removed from the connection and on the server side when a new -command has been started. - - -So, before writing, the buffer contains a sequence of logical -packets, consisting of header plus data consecutively. If compression -is used, packet numbers are not stored in each header of the logical -packets, but a whole buffer, or a part of it if flushing is done, -containing one or more logical packets are compressed. In that case -a new larger header, is formed, and all logical packets contained -in the buffer are compressed together. This way only one packet is -formed which makes several logical packets, which improves both -speed and compression ratio. On the other side, when this large -compressed packet is read, it is first uncompressed, and then logical -packets are sent, one by one, to the calling functions. - - -All this functionality is described in detail in the following -chapter. It does not contain functions that form logical packets, or -that read and write to connections but also functions that are used -for initialization, clearing of connections. There are functions at -higher level dealing with sending fields, rows, establishing -connections, sending commands, but those are not explained in the -following chapter. - - -Functions utilized in client/server protocol --------------------------------------------- - -First of all, functions are described that are involved in preparing, -reading, or writing data over TCP port, Unix socket file, or named -pipe, and functions directly related to those. All of these functions -are used both in server and client. Server and client specific code -segments are documented in each function description. - -Each MySQL function checks for errors in memory allocation and -freeing, as well as in every OS call, like the one dealing with -files and sockets, and for errors in indigenous MySQL function -calls. This is expected, but has to be said here so as not to repeat -it in every function description. - -Older versions of MySQL have utilized the following macros for -reading from or writing to a socket. - -raw_net_read - calls OS function recv function that reads N bytes -from a socket into a buffer. Number of bytes read is returned. - -raw_net_write - calls OS function send to write N bytes from a -buffer to socket. Number of bytes written is returned. - -These macros are replaced with VIO (Virtual I/O) functions. - - -Function name: my_net_init - -Parameters: struct NET *, enum_net_type, struct Vio - -Return value: 1 for error, 0 for success - -Function purpose: To initialize properly all NET fields, - allocate memory and set socket options - -Function description - -First of all, buff field of NET struct is allocated to the size of -net_buffer_length, and on failure function exits with 0. All fields -in NET are set to their default or starting values. As net_buffer_length -and max_allowed_packet are configurable, max_allowed_packet is set -equal to net_buffer_length if the latter one is greater. max_packet -is set for that NET to net_buffer_length, and buff_end points to -buff end. vio field is set to the second parameter. If it is a -real connection, which is the case when second parameter is not -null, then fd field is set by calling vio_fd function. read_pos and -write_pos to buff, while remaining integers are set to 0. If function -is run on the MySQL server on Unix and server is started in a test -mode that would require testing of blocking, then vio_blocking -function is called. Last, fast throughput mode is set by a call to -vio_fastsend function. - - -Function name: net_end - -Parameters: struct NET * - -Return value: void - -Function purpose: To release memory allocated to buff - - - -Function name: net_realloc (private, static function) - -Parameters: struct NET, ulong (unsigned long) - -Return value: 1 for error, 0 for success - -Function purpose: To change memory allocated to buff - -Function description - -New length of buff field of NET struct is passed as second parameter. -It is first checked versus max_allowed_packet and if greater, an -error is returned. New length is aligned to 4096-byte boundary. Then, -buff is reallocated, buff_end, max_packet, and write_pas reset to -the same values as in my_net_init. - - - -Function name: net_clear (used on client side only) - -Parameters: struct NET * - -Return value: void - -Function purpose: To read unread packets - -Function description - -This function is used on client side only, and is executed -only if a program is not started in test mode. This function reads -unread packets without processing them. First, non-blocking mode is -set on systems that do not have non-blocking mode defined. This is -performed by checking the mode with vio_is_blocking function. and -setting non-blocking mode by vio_blocking function. If this operation -was successful, then packets are read by vio_read function, to which -vio field of NET is passed together with buff and max_packet field -values. field of the same struct at a length of max_packet. If -blocking was active before reading is performed, blocking is set with -vio_blocking function. After reading has been performed, pkt_nr is -reset to 0 and write_pos reset to buff. In order to clarify some -matters non-blocking mode enables executing program to dissociate from -a connection, so that error in connection would not hang entire -program or its thread. - -Function name: net_flush - -Parameters: struct NET * - -Return value: 1 for error, 0 for success - -Function purpose: To write remaining bytes in buff to socket - -Function description - -net_real_write (described below) is performed is write_pos -differs from buff, both being fields of the only parameter. write_pos -is reset to buff. This function has to be used, as MySQL uses buffered -writes (as will be explained more in the function net_write_buff). - - -Function name: my_net_write - -Parameters: struct NET *, const char *, ulong - -Return value: 1 for error, 0 for success - -Function purpose: Write a logical packet in the second parameter - of third parameter length - -Function description - -The purpose of this function is to prepare a logical packet such -that entire content of data, pointed to by second parameter and in -length of third parameter is sent to the other side. In case of -server, it is used for sending result sets, and in case of client -it is used for sending local data. This function foremost prepares -a header for the packet. Normally, the header consists of 4 bytes, -of which the first 3 bytes contain the length of the packet, thereby -limiting a maximum allowable length of a packet to 16MB, while the -fourth byte contains the packet number, which is used when one large -packet has to be divided into sequence of packets. This way each -sub-packet gets its number which should be matched on the other -side. When compression is used another three bytes are added to -packet header, thus packet header is in that case increased to 7 -bytes. Additional three bytes are used to save the length of -compressed data. As in connection that uses compression option, -code packs packets together,, a header prepared by this function -is later not used in writing to / reading from network, but only -to distinguish logical packets within a buffered read operation. - - -This function, first stores the value of the third parameter into the -first 3 bytes of local char variable of NET_HEADER_SIZE size by usage -of function int3store. Then, at this point, if compression is not -used, pkt_nr is increased, and its value stored in the last byte of -the said local char[] variable. If compression is used, 0 is stored in -both values. Then those four bytes are sent to other side by the usage -of the function net_write_buff(to be explained later on), and if -successful, entire packet in second parameter of the length described -in third parameter is sent by the usage of the same function. - - -Function name: net_write_command - -Parameters: struct NET *, char, const char *, ulong - -Return value: 1 for error, 0 for success - -Function purpose: Send a command with a packet as in previous function - -Function description - -This function is very similar to the previous one. The only -difference is that first packet is enlarged by one byte, so that the -command precedes the packet to be sent. This is implemented by -increasing first packet by one byte, which contains a command code. As -command codes do not use the range of values that are used by character -sets, so when the other side receives a packet, first byte after -header contains a command code. This function is used by client for -sending all commands and queries, and by server in connection process -and for sending errors. - - -Function name: net_write_buff (private, static function) - -Parameters: struct NET *, const char *, uint - -Return value: 1 for error, 0 for success - -Function purpose: To write a packet of any size by cutting it -and using next function for writing it - -Function description - -This function was created after compression feature has been -added to MySQL. This function supposes that packets have already been -properly formatted, regarding packet header etc. The principal reason for -this function to exist is because a packet that is sent by client or -server does not have to be less than max_packet. So this function -first calculates how much data has been left in a buff, by getting a -difference between buff_end and write_pos and storing it to local -variable left_length. Then a loop is run as long as the length to be -sent is greater than length of left bytes (left_length). In a loop -data from second parameter is copied to buff at write_pos, as much as -it can be, that is, by left_length. Then net_real_write function is called -(see below) with NET, buff, and max_packet parameters. This function -is the lowest level function that writes data over established -connection. In the loop, write_pos is reset to buff, the pointer to data -(second parameter) is moved by the amount of data sent (left_length), -length of data to be sent (third parameter) is decreased by the amount -sent (left_length) and left_length is reset to max_packet value, which -ends the loop. This logic was necessary, as there could have been some -data yet unsent (write_pos != buf), while data to be sent could be as -large as necessary, thus requiring many loops. At the end of function, -remaining data in second parameter are copied to buff at write_pos, by -the remaining length of data to be sent (third parameter). So, in the -next call of this function remaining data will be sent, as buff is -used in the call to net_real_write. It is very important to note that if -a packet to be sent is less than the number of bytes that are still -available in buff, then there will be no writing over network, but -only logical packets will be added one after another. This will -accelerate network traffic, plus if compression is used, the -expected compression rate would be higher. That is why server or -client functions that sends data uses at the end of data net_flush -function described above. - - -Function name: net_real_write - -Parameters: struct NET *, const char *, ulong - -Return value: 1 for error, 0 for success - -Function purpose: To write data to a socket or pipe, with -compression if used - -Function description - -First, more field is set to 2, to enable reporting in -mysql_list_processes. Then if compression is enabled on that -connection, a new local buffer (variable b) is initialized to the -length of total header (normal header + compression header) and if no -memory is available, an error is returned. This buffer (b) is used for -holding the final, compressed packet to be written over the -connection. Furthermore in compression initialization, second -parameter at length of third parameter is copied to the local buffer -b, and MySQL's wrapped zlib's compression function is run at total -header offset of the local buffer. Please, do note that this function -does not test effectiveness of compression. If compression is turned -on in some connection, it is used all of the time. Also, it is very -important to be cognizant of the fact that this algorithm makes -possible that a single compressed packet contains several logical -packets. In this way compression rate is increased and network -throughput is increased as well. However, this algorithm has -consequences on the other side, that reads compressed packet, which -is covered in my_net_read function. After compression is done, the full -compression header is properly formed with the packet number, -compressed and uncompressed lengths. At the end of compression code, -third parameter is increased by total header length, as the original -header is not used (see above), and second parameter, pointer to data, -is set to point to local buffer b, in order that the further flow of -function is independent of compression. If a function is executed -on server side, a thread alarm initialized and if non-blocking is -active set at NET_WRITE_TIMEOUT. Two local (char *) pointers are -initialized, pos at beginning of second parameter, and end at end of -data. Then the loop is run as long as all data is written, which means -as long as pos != end. First vio_write function is called, with -parameters of vio field, pos and size of data (end - pos). Number of -bytes written over connection is saved in local variable (length). If -error is returned local bool variable (interrupted) is set according -to the return value of the vio_should_retry called with vio field as -parameter. This bool variable indicates whether writing was -interrupted in some way or not. - -Further, error from vio_write is treated differently on Unix versus -other OS's (Win32 or OS/2). On Unix an alarm is set if one is not -in use, no bytes have been written and there has been no interruption. -Also, in that case, if connection is not in blocking mode, a sub-loop -is run as long as blocking is not set with vio_blocking function. -Within the loop another run of above vio_write is run based on -return value of vio_is_retry function, provided number of repeated -writes is less than RETRY_COUNT. If that is not the case, error -field of struct NET is set to 1 and function exits. At the exit -of sub-loop number of reruns already executed is reset to zero and -another run of above vio_write function is attempted. If the function -is run on Win32 and OS/2, and in the case that function flow was -not interrupted and thread alarm is not in use, again the main loop -is continued until pos != end. In the case that this function is -executed on thread safe client program, a communication flow is -tested on EINTR, caused by context switching, by use of vio_errno -function, in which case the loop is continued. At the end of -processing of the error from vio_write, error field of struct NET -is set, and if on server last_errno field is set to -ER_NET_WRITE_INTERRUPTED in the case that local bool variable -(interrupted) is true or to ER_NET_ERROR_ON_WRITE. Before the end -of loop, in order to make possible evaluation of the loop condition, -pos is increased by the value written in last iteration (length). -Also global variable bytes_sent is increased by the same value, for -status purposes. At the end of the functions more fields is reset, -in case of compression, compression buffer (b) memory is released -and if thread is still in use, it is ended and blocking state is -reset to its original state, and function returns error is all bytes -are not written. - - - -Function name: my_real_read (private, static function) - -Parameters: struct NET *, ulong * - -Return value: length of bytes read - -Function purpose: low level network connection read function - -Function description - -This function has made as a separate one when compression was -introduced in MySQL client/server protocol . It contains basic, low -level network reading functionality, while all dealings with -compressed packets are handled in next function. Compression in this -function is only handled in as much to unfold the length of uncompressed -data. First blocking state of connection is saved in local bool -variable net_blocking, and field more is set 1 for detailed reporting -in mysqld_list_processes. A new thread alarm is initialized, in order -to enable read timeout handling, and if on server and a connection can -block a program, the alarm is set at a value of timeout field. Local -pointer is set to the position of the next logical packet, with its -header skipped, which is at field where_b offset from buff. Next, a -two time run code is entered. A loop is run exactly two times because -first time number of bytes to be fetched (remain) are set to the -header size, which is different when compression is used or not used -on the connection. After first fetch has been done, number of packets -that will be received in second iteration is well known, as fetched -header contains the size of packet, packet number, and in the case of -compression, the size of the uncompressed packet. Then, as long as there are -bytes to read the loop is entered with first reading data from network -connection with vio_read function, called with parameters of field -vio, current position and remaining number of bytes, which value is -hold by local variable (remain) initialized at the value of header size, -which differs if compression is used. Number of bytes read are -returned in local length variable. If error is returned local bool -variable (interrupted) is set according to the return value of the -vio_should_retry called with vio field as parameter. This bool -variable indicates whether reading was interrupted in some way or not. - -Further, error from vio_read is treated differently on Unix versus -other OS's (Win32 or OS/2). On Unix an alarm is set if one is not -in use, no bytes have been read and there has been no interruption. -Also, in that case, if connection is not in blocking mode, a sub-loop -is run as long as blocking is not set with vio_blocking function. -Within the loop another run of above vio_read is run based on return -value of vio_is_retry function, provided number of repeated writes -is less than RETRY_COUNT. If that is not the case, error field of -struct NET is set to 1 and function exits. At the exit of sub-loop -number of reruns already executed is reset to zero and another run -of above vio_read function is attempted. If the function is run on -Win32 and OS/2, and in the case that function flow was not interrupted -and thread alarm is not in use, again the main loop is continued -as long as there are bytes remaining. In the case that this function -is executed on thread safe client program, then if another run -should be made, which is decided by the output of vio_should_retry -function, in which case the loop is continued. At the end of -processing of the error from vio_read, error field of struct NET -is set, and if on server last_errno field is set to ER_NET_READ_INTERRUPTED -in the case that local bool variable (interrupted) is true or to -ER_NET_ERROR_ON_READ. In case of such an error this function exits -and returns error. In the case when there is no error, number of -remaining bytes (remain) is decreased by the number of bytes read, -which should be zero, but in case it is not the entire code is still -in while (remain > 0) loop, which will be exited immediately if it -is. This has been done to accommodate errors in the traffic level -and for the very slow connections. Current position in field buff -is also moved by the amount of bytes read by vio_read function, and -global variable bytes_received is increased by the same value in a -thread safe manner. When the loop that is run until necessary bytes -are read (remain) is finished, then if external loop is in its first -run, of the two, packet sequencing is tested for consistency by -comparing the number contained at 4th byte in header with pkt_nr -field. Header location is found at where_b offset to field_b. Usage -of where_b is obligatory due to the possible compression usage. If -there is no compression on a connection, then where_b is always 0. -If there is a discrepancy, then first byte of the header is checked -whether it is equal to 255, because when error is sent by the server, -or by a client if it is sending data (like in LOAD DATA INFILE -LOCAL...), then first byte in header is set to 255. If it is not -255, then an error on packets being out of order is printed. In any -case, on server, last_errno field is set to ER_NET_PACKETS_OUT_OF_ORDER -and the function returns with an error, that is, the value returned is -packet_error. If a check on serial number of packet is successful, -pkt_nr field is incremented in order to enable checking packet order -with next packet and if compression is used, uncompressed length -is extracted from a proper position in header and returned in the -second parameter of this function. Length of the packet is saved, -for the purpose of a proper return value from this function. Still -in the first iteration of the main loop, a check must be made if -field buff could accommodate entire package that comes, in its -compressed or uncompressed form. This is done in such a way, because -zlib's compress and uncompress functions use the same memory area -for compression and uncompression. Necessary field buff length is -equal to current offset where data are (where_b which is zero for -non-compression), plus the larger value of compressed or uncompressed -package to be read in a second run. If this value is larger than -the current length of field buff, which is read from field max_packet, -then field buff has to be reallocated. If reallocation with net_realloc -function fails, the function returns an error. Before a second -loop is started, length to be read is set to the length of expected -data and current position (pos) is set at where_b offset from field -buff. At the end of function, if alarm is set, which is the case -if it is run on server or on a client if a function is interrupted -and another run of vio_read is attempted, alarm is ended and blocking -state is restored from the saved local bool variable net_blocking. -Function returns number of bytes read or the error (packet_error). - - -Function name: my_net_read - -Parameters: struct NET * - -Return value: length of bytes read - -Function purpose: Highest level general purpose reading function - -Function description - -First, if compression is not used, my_real_read is called, with -struct NET * a first parameter, and pointer to local ulong complen -as a second parameter, but its value is not used here. Number of -bytes read is returned in local ulong variable len. read_pos field -is set to an offset of value of where_b field from field buff. -where_b field actually denotes where in field buff is the current -packet. If returned number of bytes read (local variable len) does -not signal that an error in packet transmission occurred (that is, -it is not set to packet_error), then the string contained in read_pos -is zero terminated. Simply, the end of the string starting at -read_pos, and ending at read_pos + len, is set to zero. This is -done in that way, because mysql_use_result expects a zero terminated -string, and function returns with a value local variable len. This -ends this function in the case that compression is not used and the -remaining code is executed only if compression is enabled on the -connection. - -In order to explain how a compressed packet logically is cut into -meningful packets, the full meaning of several NET fields should -be explained. First of all, fields in NET are used and not local -variables, as all values should be saved between consecutive calls -of this function. Simply, this function is called in order to return -logical packets, but this function does not need to call my_real_read -function everytime, because when a large packet is uncompressed, -it may, but not necessarily so, contain several logical packets. -Therefore, in order to preserve data on logical packets local -variables are not used. Instead fields in NET struct are used. Field -remain_in_buf denotes how many bytes of entire uncompressed packets -is still contained within buff. field buf_length saves the value -of the length of entire uncompressed packet. field save_char is -used to save the character at the position where the packet ends, -which character has to be replaced with a zero, '\0', in order to -make a logical packet zero delimited, for mysql_use_result. Field -length stores the value of the length of compressed packet. Field -read_pos as usual, points to the current reading position. This -char * pointer is used by all functions that call this function in -order to fetch their data. Field buff is not used for that purpose, -but read_pos is used instead. This change was introduced with -compression, when algorithm accommodated grouping of several packets -together. - -Now that meanings of all relevant NET fields are explained, -we can proceed with the flow of this function for the case when -compression is active. First, if there are remaining portions of -compressed packet in a field buff, saved character value is set at -the position where zero char '\0' was inserted to enable the string -to be zero delimited for mysql_use_result. Then a loop is started. -In the first part of the loop, if there are remaining bytes, local -uchar *pos variable is set at the current position in field buff -where a new packet starts. This position is an (buf_length - -remain_in_buf) offset in field buff. As it is possible that next -logical packet is not read to the full length in the remaining of -the field buf, several things had to be inspected. It should be -noted that data that is read from net_real_read contains only logical -packets containing 4 byte headers only, being 4 byte headers prepared -by my_net_write or net_write_command. But, when written, logical -packet could be so divided that only a part of header is read in. -Therefore after pointer to the start of the next packet has been -saved, a check is made whether number of remaining bytes in buffer -is less than 4, being 3 bytes for length and one byte for packet -number. If it is greater, then the length of the logical packet is -extracted and saved a length field. Then a check is made whether -entire packet is contained within a buf, that is, a check is made -that the logical packet is fully contained in the buffer. In that -case, number of bytes remaining in buffer is decreased by the full -length of logical packet (4 + length field), read_pos is moved -forward by 4 bytes to skip header and be set at a beginning of data -in logical packet, length field is saved for the value to be returned -in function and the loop is exited. In the case that the entire -logical packet is not contained within the buffer, then if length of -the entire buffer differs from remaining length of logical packet, -it (logical packet) is moved to the beginning of the field buff. -If length of the entire buffer equals the remaining length of logical -packet, where_b and buf_length fields are set to 0. This is done -so that in both cases buffer is ready to accept next part of packet. - -In order to get a next part of a packet, still within a loop, -my_real_read function is called and length of compressed packet is -returned to a local len variable, and length of compressed data is -returned in complen variable. In the case of non-compression value -of complen is zero. If packet_error is from my_real_read function, -this function returns also with packet_error. If it is not a -packet_error, my_uncompress function is called to uncompress data. -It is called with offset of where_b data from field buff, as it is -the position where compressed packet starts, and with len and complen -values, being lengths of compressed and uncompressed data. If there -is no compression, 0 is returned for uncompressed size from -my_real_read function, and my_uncompress wrapper function is made -to skip zlib uncompress in that case. If error is returned from -my_uncompress, error field is set to 1, if on server last_errno is -set to ER_NET_UNCOMPRESS_ERROR and loop is exited and function -returns with packet_error. If not, buf_length and remain_in_buf -fields are set to the uncompressed size of buffer and the loop is -continued. When the loop is exited save_char field is used to save -the char at end of a logical packet, which is an offset of field -len from position in field buff pointed by field read_pos, in order -that zero char is set at the same position, for mysql_use_result. -Function returns the length of the logical packet without its header. |