MySQL Administrator''''s Bible- P17

MySQL Proxy ATABLE A-5 continued COM_SET_OPTION string.bytepacket This packet contains a set command... Description BIT_ANDexpr No Bitwise AND; returns true if all rows are true and fal

MySQL Proxy A

TABLE A-5 (continued )

[x].type

The backend server was definedwith proxy-backend-address

This packet was successful

MYSQLD_PACKET_RAW proxy.response.type This packet contains raw

hex 0x00700 corresponds toversion 0.7.0

COM_SLEEP string.byte(packet) This packet contains a sleep

COM_STATISTICS string.byte(packet) This packet contains a

statistics command.COM_PROCESS_INFO string.byte(packet) This packet contains a

process info command

connect command.COM_PROCESS_KILL string.byte(packet) This packet contains a kill

COM_DELAYED_INSERT string.byte(packet) This packet contains a

delayed insert command.COM_CHANGE_USER string.byte(packet) This packet contains a

change user command.COM_BINLOG_DUMP string.byte(packet) This packet contains a

binlog dump command.COM_TABLE_DUMP string.byte(packet) This packet contains a table

dump command

COM_CONNECT_OUT string.byte(packet) This packet contains a

connect out command.COM_REGISTER_SLAVE string.byte(packet) This packet contains a

register slave command.COM_STMT_CLOSE string.byte(packet) This packet contains a close

string.byte(packet) This packet contains a send

long data command.COM_STMT_RESET string.byte(packet) This packet contains a reset

command

MySQL Proxy A

TABLE A-5 (continued )

COM_SET_OPTION string.byte(packet) This packet contains a set

command

MYSQL_TYPE_NEWDECIMAL proxy.response

resultset { field{{type,name}} }

This field has a type ofDECIMAL

resultset { field{{type,name}} }

This field has a type ofTINY

resultset { field{{type,name}} }

This field has a type ofSHORT

resultset { field{{type,name}} }

This field has a type ofLONG

resultset { field{{type,name}} }

This field has a type ofFLOAT

resultset { field{{type,name}} }

This field has a type ofDOUBLE

resultset { field{{type,name}} }

This field has a type ofNULL

MYSQL_TYPE_TIMESTAMP proxy.response

resultset { field{{type,name}} }

This field has a type ofTIMESTAMP

MYSQL_TYPE_LONGLONG proxy.response

resultset { field{{type,name}} }

This field has a type ofLONGLONG

resultset { field{{type,name}} }

This field has a type of INT

resultset { field{{type,name}} }

This field has a type ofDATE

resultset { field{{type,name}} }

This field has a type ofTIME

continued

MYSQL_TYPE_DATETIME proxy.response.

resultset { field{{type,name}} }

This field has a type ofDATETIME

resultset { field{{type,name}} }

This field has a type ofYEAR

resultset { field{{type,name}} }

This field has a type ofNEWDATE

resultset { field{{type,name}} }

This field has a type ofENUM

resultset { field{{type,name}} }

This field has a type of SET

MYSQL_TYPE_TINY_BLOB proxy.response

resultset { field{{type,name}} }

This field has a type ofTINY_BLOB

MYSQL_TYPE_

MEDIUM_BLOB

proxy.response

resultset { field{{type,name}} }

This field has a type ofMEDIUM_BLOB

MYSQL_TYPE_LONG_BLOB proxy.response

resultset { field{{type,name}} }

This field has a type ofLONG_BLOB

resultset { field{{type,name}} }

This field has a type ofBLOB

MYSQL_TYPE_VAR_STRING proxy.response

resultset { field{{type,name}} }

This field has a type ofVAR_STRING

resultset { field{{type,name}} }

This field has a type ofSTRING

MYSQL_TYPE_GEOMETRY proxy.response

resultset { field{{type,name}} }

This field has a type ofGEOMETRY

resultset { field{{type,name}} }

This field has a type of BIT

MySQL Proxy Internal Structures

connection backend_ndx

send_queueusernameaddressscrambled_password

mysqld_versionscramble_buffer

addressstatetype

usersservers

queue

continued

type

rowsrrrmsg

packet

texttoken_idtoken_name

Theproxy.global.configstructure can be extended to store user-defined variables For example, therw-splitting.luasample script extends theproxy.global.configstructure

to include:

■ proxy.global.config.rwsplit

■ proxy.global.config.rwsplit.min_idle_connections

■ proxy.global.config.rwsplit.max_idle_connections

MySQL proxy tokens

The proxy tokenizer has a set of tokens that it uses to define parts of a statement The

‘‘Proxy Tokenizer’’ section earlier showed a few such tokens, including ones for punctuation (TK_OBRACE,TK_CBRACE,TK_DOT,TK_STAR), type (TK_LITERAL,TK_STRING), and SQL keywords (TK_SQL_SELECT,TK_SQL_FROM,TK_SQL_WHERE,TK_SQL_LIKE).

The tokens inmysql-proxy0.6 0 that are not SQL statement keywords can be found in the source code filesql-tokenizer.cand are listed in Table A-7.

The SQL keyword tokens inmysql-proxy0.6.0 are also found in the source code filesql-tokenizer.cand are listed in Table A-8 There are no examples given, because each token name is the keyword withTK_SQL_appended For example, the tokenTK_SQL_ALTERcorresponds to the SQL keywordALTER.

MySQL Proxy A

TABLE A-7

MySQL Proxy Tokens

VARIABLES, etc.)

@and @@ variables Database, table, and column names

continued

MySQL Proxy A

TABLE A-8 (continued )

SQL Statement Keywords

TK_SQL_BINARYTK_SQL_BITTK_SQL_BLOBTK_SQL_BOTHTK_SQL_BYTK_SQL_CALLTK_SQL_CASCADETK_SQL_CASETK_SQL_CHANGETK_SQL_CHARTK_SQL_CHARACTERTK_SQL_CHECKTK_SQL_COLLATETK_SQL_COLUMNTK_SQL_CONDITIONTK_SQL_CONSTRAINTTK_SQL_CONTINUETK_SQL_CONVERTTK_SQL_CREATETK_SQL_CROSSTK_SQL_CURRENT_DATETK_SQL_CURRENT_TIMETK_SQL_CURRENT_TIMESTAMPTK_SQL_CURRENT_USERTK_SQL_CURSORTK_SQL_DATABASETK_SQL_DATABASESTK_SQL_DATE

continued

TK_SQL_DECIMALTK_SQL_DECLARETK_SQL_DEFAULTTK_SQL_DELAYEDTK_SQL_DELETETK_SQL_DESCTK_SQL_DESCRIBETK_SQL_DETERMINISTICTK_SQL_DISTINCTTK_SQL_DISTINCTROWTK_SQL_DIV

TK_SQL_DOUBLETK_SQL_DROPTK_SQL_DUALTK_SQL_EACHTK_SQL_ELSETK_SQL_ELSEIFTK_SQL_ENCLOSEDTK_SQL_ENUMTK_SQL_ESCAPEDTK_SQL_EXISTSTK_SQL_EXITTK_SQL_EXPLAINTK_SQL_FALSE

MySQL Proxy A

TABLE A-8 (continued )

SQL Statement Keywords

TK_SQL_FETCHTK_SQL_FLOATTK_SQL_FLOAT4TK_SQL_FLOAT8TK_SQL_FORTK_SQL_FORCETK_SQL_FOREIGNTK_SQL_FROMTK_SQL_FULLTEXTTK_SQL_GRANTTK_SQL_GROUPTK_SQL_HAVINGTK_SQL_HIGH_PRIORITYTK_SQL_HOUR_MICROSECONDTK_SQL_HOUR_MINUTETK_SQL_HOUR_SECONDTK_SQL_IF

TK_SQL_IGNORETK_SQL_INTK_SQL_INDEXTK_SQL_INFILETK_SQL_INNERTK_SQL_INOUTTK_SQL_INSENSITIVETK_SQL_INSERTTK_SQL_INTTK_SQL_INT1TK_SQL_INT2

continued

TK_SQL_LONGTK_SQL_LONGBLOBTK_SQL_LONGTEXTTK_SQL_LOOPTK_SQL_LOW_PRIORITYTK_SQL_MASTER_SSL_VERIFY_SERVER_CERT

MySQL Proxy A

TABLE A-8 (continued )

SQL Statement Keywords

TK_SQL_MATCHTK_SQL_MEDIUMBLOBTK_SQL_MEDIUMINTTK_SQL_MIDDLEINTTK_SQL_MINUTE_MICROSECONDTK_SQL_MINUTE_SECONDTK_SQL_MOD

TK_SQL_MODIFIESTK_SQL_NATURALTK_SQL_NOTK_SQL_NOTTK_SQL_NO_WRITE_TO_BINLOGTK_SQL_NULL

TK_SQL_NUMERICTK_SQL_ONTK_SQL_OPTIMIZETK_SQL_OPTIONTK_SQL_OPTIONALLYTK_SQL_OR

TK_SQL_ORDERTK_SQL_OUTTK_SQL_OUTERTK_SQL_OUTFILETK_SQL_PRECISIONTK_SQL_PRIMARYTK_SQL_PROCEDURETK_SQL_PURGETK_SQL_RANGE

continued

TK_SQL_SENSITIVETK_SQL_SEPARATORTK_SQL_SETTK_SQL_SHOWTK_SQL_SMALLINTTK_SQL_SPATIALTK_SQL_SPECIFICTK_SQL_SQL

MySQL Proxy A

TABLE A-8 (continued )

SQL Statement Keywords

TK_SQL_SQL_BIG_RESULTTK_SQL_SQL_CALC_FOUND_ROWSTK_SQL_SQLEXCEPTION

TK_SQL_SQL_SMALL_RESULTTK_SQL_SQLSTATE

TK_SQL_SQLWARNINGTK_SQL_SSL

TK_SQL_STARTINGTK_SQL_STRAIGHT_JOINTK_SQL_TABLE

TK_SQL_TERMINTEDTK_SQL_TEXTTK_SQL_THENTK_SQL_TIMETK_SQL_TIMESTAMPTK_SQL_TINYBLOBTK_SQL_TINYINTTK_SQL_TINYTEXTTK_SQL_TOTK_SQL_TRAILINGTK_SQL_TRIGGERTK_SQL_TRUETK_SQL_UNDOTK_SQL_UNIONTK_SQL_UNIQUETK_SQL_UNLOCKTK_SQL_UNSIGNEDTK_SQL_UPDATE

continued

TK_SQL_VARBINARYTK_SQL_VARCHARTK_SQL_VARCHARACTERTK_SQL_VARYINGTK_SQL_WHENTK_SQL_WHERETK_SQL_WHILETK_SQL_WITHTK_SQL_WRITETK_SQL_X509TK_SQL_XORTK_SQL_YEAR_MONTHTK_SQL_ZEROFILL

Summary

In this appendix you have learned how to use the MySQL Proxy, including:

■ Using multiple backends with MySQL Proxy

■ How MySQL Proxy’s default round-robin connection logic works

■ A brief Lua tutorial

■ How MySQL Proxy tokenizes queries

■ Query injection with MySQL Proxy

■ Reference material for more advanced MySQL Proxy scripting

Functions and Operators

IN THIS APPENDIX

Using aggregation functions Using bitwise operators Compressing and encrypting data

Testing, logic, and control flow Using server-level functions Working with data types

T his appendix contains the functions and operators available in

MySQL, including whether they are an SQL Standard or a MySQL Extension.

Using Aggregation Functions

Aggregation functions take a single expression as an argument

but may take input from many rows; they are row-wise functions.

For example, theAVG(expr)function takes a simple average (the sum divided by the count):

mysql> CREATE TABLE nums (num TINYINT);

Query OK, 0 rows affected (0.09 sec)mysql> INSERT INTO nums (num) VALUES (1),(2),(3);

Query OK, 3 rows affected (0.48 sec)Records: 3 Duplicates: 0 Warnings: 0mysql> select AVG(num) FROM nums;

+ -+

| AVG(num) |+ -+

| 2.0000 |+ -+

1 row in set (0.03 sec)Although aggregate functions work on expressions that encompass one or more rows, they only take one expression as an

argument For example, the syntax of AVG(expr)does not allow for the following:

right syntax to use near ’2,3)’ at line 1

One exception to this rule is that COUNT(DISTINCT expr) can take multiple arguments.

Whenexprevaluates asNULL, for example when there are no rows that match, most gation functions returnNULL Functions that return 0 whenexprevaluates asNULLareCOUNT(*),COUNT(expr),COUNT(DISTINCT expr),BIT_OR, andBIT_XOR.

aggre-Bug

There is one function that returns an unexpected result:BIT_AND(NULL):

mysql> SELECT BIT_AND(NULL);

+ -+

+ -+

| 18446744073709551615 |+ -+

1 row in set (0.00 sec)

For the curious,18446744073709551615is a 63-bit string where each bit is 1 This has beenreported as MySQL bug 37754 and can be seen at:http://bugs.mysql.com/bug.php?

id=37754

Table B-1 lists the aggregate functions and a brief description of each one.

Using Bitwise Operators

MySQL extends standard SQL with special functions for bits Bitwise operators implicitly cast arguments toUNSIGNED BIGINT This has the most noticeable effect on bit inversion (∼):mysql> SELECT 5,∼5,BIN(5),BIN(∼5)\G

*************************** 1 row ***************************5: 5

∼5: 18446744073709551610BIN(5): 101

BIN(∼5): 1111111111111111111111111111111111111111111111111111111111111010

1 row in set (0.00 sec)Aggregation functions for bits are listed in Table B-1.

Functions and Operators B

TABLE B-1

Aggregation FunctionsFunction Syntax Standard

SQL?

Description

BIT_AND(expr) No Bitwise AND; returns true if all rows are true and false if

any rows are false

BIT_OR(expr) No Bitwise OR; returns true if any row is true; returns false if

all rows are false

BIT_XOR(expr) No Bitwise XOR; a pair where exactly one value is true

returns true; all other pairs will return false More than 2rows are done commutatively

COUNT(expr)COUNT(*)COUNT(DISTINCT expr)

YesYesYes

Returns a count of all non-NULL values of expr

COUNT(*)returns a count of all rows

COUNT(DISTINCT expr)returns a count of how manyrows contain different values for expr

GROUP_CONCAT(expr) No Concatenates non-NULL values, separated by a comma

by default

STD(expr) No Nonstandard SQL equivalent to STDDEV_POP(expr)

STDDEV_POP(expr) Yes Population standard deviation Same as

SQRT(VAR_POP(expr))

STDDEV_SAMP(expr) Yes Sample standard deviation Same as

SQRT(VAR_SAMP(expr))

STDDEV(expr) No Nonstandard SQL equivalent to STDDEV_POP(expr)

SUM(expr) Yes Returns the sum of all values of expr

VAR_POP(expr) Yes Population standard variance This is calculated by taking

the average of the square of the differences betweeneach value and the average value

VAR_SAMP(expr) Yes Population standard variance This is calculated by taking

the sum of the square of the differences between eachvalue and the average value, and dividing by the number

of values (rows) minus one

VARIANCE(expr) No Nonstandard SQL equivalent to VAR_POP(expr)

TABLE B-2

Bit FunctionsFunction

Syntax

Standard SQL?

Description

& No Bitwise AND, returns true when both bit positions are true

| No Bitwise OR, returns true when either or both bit positions are true

ˆ No Bitwise XOR, returns true when exactly one bit position is true

<< No Shifts to the left

>> No Shifts to the rightBIT_COUNT No Returns the number of bits that are set

Combining multiple statements

Much like basic arithmetic operators (such as + - * / ), these bitwise operators can be combined into longer statements, which are then parsed using precedence rules.

Precedence from highest to least is shown in Table B-3.

TABLE B-3

Bit Operator Precedence

Let’s walk through an example:

mysql> SELECT 5 | 2 ˆ 7 << 3 | 4 & 6;

+ -+

Functions and Operators B

| 5 | 2 ˆ 7 << 3 | 4 & 6 |+ -+

1 row in set (0.00 sec)The expression is now:

101 | ((10 ˆ 111) << 11) | (100 & 110)The first operation is10 ˆ 111, which evaluates to101, or5in base 10.

101 | (101 << 11) | (100 & 110)

101 << 11shifts the bits in 101 to the left by three positions to produce101000, or40in base 10.

101 | 101000 | (100 & 110)Evaluating the remaining expression in parenthesis,100 & 110equates to100, or4in base 10.

101 | 101000 | 100Just like arithmetic operators, it is standard to evaluate from left to right when all the operators have the same precedence.101 | 101000evaluates to101101, or45in base 10, which leaves the expression as:

101 | 101101The remaining expression101 | 101101evaluates to101101for a final result of 45.

The binaries from MySQL are compiled with compression libraries If MySQL is not compiled with a compression library, compression functions will returnNULL Table B-4 lists the compres- sion functions and a brief description of each one.

TABLE B-4

Compression FunctionsFunction Syntax Standard SQL? Description

COMPRESS(expr) No Returns the compressed value of exprUNCOMPRESS(expr) No Returns the uncompressed value of expr Returns

NULLif expr is not a compressed value

UNCOMPRESSED_

LENGTH(expr)

No Returns the length of expr before compression

UNCOMPRESSED_LENGTH(COMPRESS(expr))isequivalent to LENGTH(expr)

SQL?

Description

AES_DECRYPT(str,key)

No Returns the result of AES decryption of str using key

AES_DECRYPT(AES_ENCRYPT(x,y),y)is equivalent to x.AES_ENCRYPT

(str,key)

No Returns the AES encryption of str using key Returns NULL if

either str or key is NULL Uses 128-bit keys by default; thiscan be increased to 256-bit keys by modifying the source code.DECODE

(str,pass)

No Returns the result of decoding str using a password of pass

DECODE(ENCODE(x,y),y)is equivalent to x

DES_DECRYPT(str[,key])

No Returns the result of decoding str using key See

DES_ENCRYPT()for a description of how key is used as thekey string or key number

Functions and Operators B

No Returns the Triple-DES encryption of str If key is a string, key

is used as the key string If key is a number from 0–9, the keystring is the key number from the DES key file If key is notspecified, the first key number from the DES key file is used forencryption

ENCODE(str,pass)

No Returns the result of encoding str with a password of pass

ENCRYPT(str[,pass])

No Returns the encryption of str with a salt of pass, using the

UNIX function crypt() Returns NULL on systems that do nothave crypt(), including Windows

MD5(str) No Returns the 32-character hex string representing the 128-bit

MD5 checksum of str, for non-NULL values of str ReturnsNULLif str is equivalent to NULL

OLD_PASSWORD(str)

No Returns the old, pre-MySQL 4.1 of the PASSWORD function

applied to str Used to generate password hashes on newerdatabase servers that need to support older clients/clientlibraries See PASSWORD

PASSWORD(str) No Returns the one-way password hash of str Used in the

MySQL privilege system Pre-MySQL 4.1, the encryption isweaker (see the OLD_PASSWORD)

SHA1(str),SHA(str)

No Returns the 40-character hex string representing the 160-bit

SHA1 checksum of str, for non-NULL values of str ReturnsNULLif str is equivalent to NULL

SHA2(str,bit_length)

No Added in MySQL version 6.0.5 Acceptable values for the

required bit_length field are 224, 256, 384 and 512, whichwill return the 224-bit, 256-bit, 384-bit and 512-bit SHA2checksums for non-NULL values of str, respectively ReturnsNULLif str is equivalent to NULL

Testing, Logic, and Control Flow

SQL would be much less powerful without the filtering power of comparison operators and the ability to test and control procedural flow Table B-6 lists the comparison functions and a brief description of each one.

Comparison FunctionsFunction Syntax Standard

SQL?

Description

expr1 BETWEENexpr2 AND expr3

No Equivalent to expr1>=expr2 AND expr1<=expr3

COALESCE(list) Yes Returns the first non-null value in a list containing one or

more expressionsexpr1 <=> expr2 No Returns true if expr1 equals expr2, including if they are

both NULL (NULL-safe)expr1 = expr2 Yes Returns true if expr1 equals expr2; not NULL-safeexpr1 >= expr2 Yes Returns true if expr1 is greater than or equal to expr2; not

NULL-safeexpr1 > expr2 Yes Returns true if expr1 is greater than expr2GREATEST(list) No Returns the greatest value of a list containing two or more

expressionsexpr1 IN(list) No Returns true if the value of expr1 is contained in a list of

one or more expressionsINTERVAL(list) No The list argument is two or more integer values separated

by commas When INTERVAL is called it returns a countthe number of integers in the list that are smaller in valuethan the initial integer If there are no smaller integers in thelist than the first value a 0 is returned

expr IS NOT NULL Yes Returns true if expr is not equivalent to NULLexpr IS NOT bool Yes Returns true if the Boolean value of expr is equivalent to

boolexpr IS NULL Yes Returns true if expr is equivalent to NULLexpr IS bool Yes Returns true if the Boolean value of expr is equivalent to

boolISNULL(expr) No Returns true if expr is equivalent to NULL Nonstandard

SQL equivalent to expr IS NULLLEAST(list) No Returns the least value of a list containing two or more

expressionsexpr1 <= expr2 Yes Returns true if expr1 is less than or equal to expr2; not

NULL-safeexpr1 < expr2 Yes Returns true if expr1 is less than expr2

Functions and Operators B

Yes Returns true if expr matches pattern; pattern uses SQL

regular expressions The default escape character is ‘‘\’’,used to match the literal values of the wildcard characters

‘‘%’’ and ‘‘_’’ The optional ESCAPE parameter sets theescape character to char

expr1 != expr2expr1 <> expr2

NoYes

Returns true if expr1 is not equivalent to expr2

expr1 SOUNDS LIKEexpr2

No Equivalent to SOUNDEX(expr1)= SOUNDEX(expr2) (see

CASE WHEN test1 THENexpr1 [WHEN test2 THENexpr2 ] [ELSEexprN] END

No Returns the exprX of the first testX that matches val

If no testX matches and an optional ELSE statement isdefined, returns exprN If no testX matches and noELSEstatement is defined, returns NULL

Returns the exprX of the first testX that evaluates astrue If no testX evaluates to true and an optional ELSEstatement is defined, returns exprN If no testXevaluates to true and no ELSE statement is defined,returns NULL

IF(expr1,expr2,expr3)

No Returns expr2 when expr1 evaluates as true Returns

expr3when expr1 evaluates as false or NULL

IFNULL(expr1, expr2) No Returns expr2 if expr1 is equivalent to NULL Returns

expr1if expr1 is not equivalent to NULL Equivalent toIF(ISNULL(expr1),expr2,expr1)

NULLIF(expr1, expr2) Yes Returns expr1 if expr1 does not equal expr2 Returns

NULLif expr1 equals expr2