Table of Contents
pgScript is composed of pgScript commands:
pgScript command : Regular PostgreSQL SQL Command (SELECT INSERT CREATE ...) | Variable declaration or assignment (DECLARE SET) | Control-of-flow structure (IF WHILE) | Procedure (ASSERT PRINT LOG RMLINE)
Command names (SELECT, IF, SET, ...) are
case-insensitive and must be ended with a semi-column ;
.
Identifiers are case-sensitive.
DECLARE @I, @T; -- Variable names begin with a @ SET @I = 0; -- @I is an integer WHILE @I < 20 BEGIN SET @T = 'table' + CAST (@I AS STRING); -- Casts @I CREATE TABLE @T (id integer primary key, data text); SET @I = @I + 1; END
DECLARE @I, @J, @T, @G; SET @I = 0; SET @G1 = INTEGER(10, 29, 1); /* Random integer generator Unique numbers between 10 and 29 */ SET @G2 = STRING(10, 20, 3); /* Random string generator 3 words between 10 and 20 characters */ WHILE @I < 20 BEGIN SET @T = 'table' + CAST (@I AS STRING); SET @J = 0; WHILE @J < 20 BEGIN INSERT INTO @T VALUES (@G1, '@G2'); SET @J = @J + 1; END SET @I = @I + 1; END
DECLARE @I, @T; -- Declaring is optional SET @I = 0; WHILE 1 -- Always true BEGIN IF @I >= 20 BREAK; -- Exit the loop if @I > 20 SET @T = 'table' + CAST (@I AS STRING); DROP TABLE @T; SET @I = @I + 1; END
SET @PROGR@M#TITLE = 'pgScript'; PRINT ''; PRINT @PROGR@M#TITLE + ' features:'; PRINT ''; PRINT ' * Regular PostgreSQL commands'; PRINT ' * Control-of-flow language'; PRINT ' * Local variables'; PRINT ' * Random data generators';
You can run ANY PostgreSQL query from a pgScript EXCEPT those ones:
BEGIN; END;
This is because BEGIN and END are used for delimiting blocks. Instead use:
BEGIN TRANSACTION; END TRANSACTION;
For a list of PostgreSQL commands: http://www.postgresql.org/docs/8.3/interactive/sql-commands.html
There are two main types of variables : simple variables and records (result sets composed of lines and columns).
Variable names begin with a @
and can be composed of
letters, digits, _
, #
, @
.
Variable type is guessed automatically according to the kind of value it contains. This can be one of: number (real or integer), string, record.
Declaring simple variable is optional.
DECLARE @A, @B; DECLARE @VAR1;
This is done with the SET command. The variable type depends on the value assigned to this variable.
SET @A = 1000, @B = 2000; -- @A and @B are integer numbers SET @C = 10e1, @D = 1.5; -- @C and @D are real numbers SET @E = 'ab', @F = 'a''b'; -- @E and @F are strings SET @G = "ab", @H = "a\"b"; -- @G and @H are strings
An uninitialized variable defaults to an empty string. It is possible to override variables as many times as wanted.
PRINT @A; -- Prints an empty string SET @A = 1000; -- @A is initialized an integer PRINT @A; -- Prints 1000 SET @A = 'ab'; -- @A becomes a string PRINT @A; -- Prints ab
Data generators allows users to generate random values. There are various types of generators, each one producing different type of data. A variable initialized with a data generator behaves like a regular simple variable except that it has a different value each time it is used.
SET @A = INTEGER(100, 200); PRINT @A; -- Prints an integer between 100 and 200 PRINT @A; -- Prints another integer between 100 and 200
A variable can contain a generator but its type is one of: number (real or integer), string. For a list of available generators and their associated type, see Random data generators.
Declaring a record is required. A name for each column must be specified even if they will not be used anymore afterwards.
DECLARE @R1 { @A, @B }, @R2 { @A, @C }; -- Two records with two columns DECLARE @R3 { @A, @B, @C, @D }; -- One record with four columns
The number of lines is dynamic: see the next section.
To access a specific location in a record, one must use the line number (starts at 0) and can use either the column name (between quotes) or the column number (starts at 0). This specific location behaves like a simple variable. Note that a record cannot contain a record.
SET @R1[0]['@A'] = 1; -- First line & first column SET @R1[0][0] = 1; -- Same location SET @R1[4]['@B'] = 1; -- Fifth line & second column SET @R1[0][1] = 1; -- Same location
In the above example, three empty lines are automatically inserted between the first and the fifth. Using an invalid column number or name results in an exception.
Specific location can be used as right values as well. A specific line can also be used as right value.
SET @R1[0][0] = @R3[0][1], @A = @R2[0][0]; -- Behaves like simple variables SET @A = @R1[1]; -- @A becomes a record which is the first line of @R1
Remember that SET @R1[0][0] = @R2
is impossible because a
record cannot contain a record.
It is possible to assign a record to a variable, in this case the variable does not need to be declared:
SET @A = @R3; -- @A becomes a record because it is assigned a record
Any SQL query executed returns a record. If the query is a
SELECT
query then it returns the results of the query. If it
is something else then it returns a one-line record (true
) if
this is a success otherwise a zero-line record (false
).
SET @A = SELECT * FROM table; -- @A is a record with the results of the query SET @B = INSERT INTO table ...; -- @B is a one-line record if the query succeeds
See Functions.
It is possible to convert a variable from one type to another with the cast function:
SET @A = CAST (@B AS STRING); SET @A = CAST (@B AS REAL); SET @A = CAST (@B AS INTEGER); SET @A = CAST (@B AS RECORD);
When a record is converted to a string, it is converted to its flat representation. When converted to a number, the record is first converted to a string and then to a number (see string conversion for more details).
When a number is converted to a string, it is converted to its string representation. When converted to a record, it is converted to a one-line-one-column record whose value is the number.
When a string is converted to a number, if the string represents a number then this number is returned else an exception is thrown. When converted to a record, either the program can find a record pattern in the string or it converts it to a one-line-one-column record whose value is the string. A record pattern is:
SET @B = '(1, "abc", "ab\\"")(1, "abc", "ab\\"")'; -- @B is a string SET @B = CAST (@B AS RECORD); @B becomes a two-line-three-column record
Remember a string is surrounded by simple quotes. Strings composing a
record must be surrounded by double quotes which are escaped with
\\
(we double the slash because it is already a special
character for the enclosing simple quotes).
Operations can only be performed between operands of the same type. Cast values in order to conform to this criterion.
Comparisons result in a number which is 0 or 1.
Comparisons: = <> > < <= >= AND OR
Concatenation: +
SET @B = @A + 'abcdef'; -- @A must be a string and @B will be a string
Boolean value: non-empty string is true
, empty string is
false
Inverse boolean value: NOT
Case-insensitive comparison: ~=
Comparisons: = <> > < <= >= AND OR
Arithmetic: + - * / %
SET @A = CAST ('10' AS INTEGER) + 5; -- '10' string is converted to a number
Boolean value: 0 is false
, anything else is
true
Inverse boolean value: NOT
(note that NOT NOT 10 =
1
)
An arithmetic operation involving at least one real number gives a real number as a result:
SET @A = 10 / 4.; -- 4. is a real so real division: @A = 2.5 SET @A = 10 / 4; -- 4 is an integer so integer division: @A = 2
Comparisons: = <> > < <= >= AND OR
Boolean value: zero-line record is false
, anything else is
true
Inverse boolean value: NOT
Comparisons for records are about inclusion and exclusion. Order of
lines does not matter. <=
means that each row in the left
operand has a match in the right operand. >=
means the
opposite. =
means that <=
and
>=
are both true at the same time...
Comparisons are performed on strings: even if a record contains numbers
like 10
and 1e1
we will have '10' <>
'1e1'
.
IF condition BEGIN pgScript commands END ELSE BEGIN pgScript commands END
pgScript commands are optional. BEGIN and END keywords are optional if there is only one pgScript command.
WHILE condition BEGIN pgScript commands END
pgScript commands are optional. BEGIN and END keywords are optional if there is only one pgScript command.
BREAK ends the enclosing WHILE loop, while CONTINUE causes the next iteration of the loop to execute. RETURN behaves like BREAK.
WHILE condition1 BEGIN IF condition2 BEGIN BREAK; END END
Conditions are in fact results of operations. For example the string
comparison 'ab' = 'ac'
will result in a number which is
false
(the equality is not true).
IF 'ab' ~= 'AB' -- Case-insensitive comparison which result in 1 (true) which is true BEGIN -- This happens END IF 0 -- false BEGIN -- This does not happen END ELSE BEGIN -- This happens END WHILE 1 BEGIN -- Infinite loop: use BREAK for exiting END
It is possible to the result of a SQL SELECT query directly as a condition. The query needs to be surrounded by parenthesis:
IF (SELECT 1 FROM table) BEGIN -- This means that table exists otherwise the condition would be false END
Procedures do not return a result. They must be used alone on a line and cannot be assigned to a variable.
Prints an expression on the screen:
PRINT 'The value of @A is' + CAST (@A AS STRING);
Throws an exception if the expression evaluated is false:
ASSERT 5 > 3 AND 'a' = 'a';
Removes the specified line of a record:
RMLINE(@R[1]); -- Removes @R second line
Functions do return a result. Their return value can be assigned to a
variable, like the CAST
operation.
Removes extra spaces surrounding a string:
SET @A = TRIM(' a '); -- @A = 'a'
Gives the number of lines in a record:
IF LINES(@R) > 0 BEGIN -- Process END
Gives the number of columns in a record:
IF COLUMNS(@R) > 0 BEGIN -- Process END
One can assign a variable (SET) with a random data generators. This means each time the variable will be used it will have a different value.
However the variable is still used as usual:
SET @G = STRING(10, 20, 2); SET @A = @G; -- @A will hold a random string SET @B = @G; -- @B will hold another random string PRINT @G, -- This will print another third random string
Common parameters for data generators are sequence and seed.
sequence means that a sequence of
values is generated in a random order, in other words each value appears
only once before the sequence starts again: this is useful for columns with
a UNIQUE
constraint. For example, this generator:
SET @G = INTEGER(10, 15, 1); -- 1 means generate a sequence
It can generate such values: 14 12 10 13 11
15 14 12 10 13 11
... Where each number appears once before the
sequence starts repeating.
sequence parameter must be an integer: if it is 0 then no sequence is generated (default) and if something other than 0 then generate a sequence.
seed is an integer value for initializing a generator: two generators with the same parameters and the same seed will generate exactly the same values.
seed must be an integer: it is used directly to initialize the random data generator.
Optional parameters are put into brackets.
Generator : INTEGER ( min, max, [sequence], [seed] ); | REAL ( min, max, precision, [sequence], [seed] ); | DATE ( min, max, [sequence], [seed] ); | TIME ( min, max, [sequence], [seed] ); | DATETIME ( min, max, [sequence], [seed] ); | STRING ( min, max, [nb], [seed] ); | REGEX ( regex, [seed] ); | FILE ( path, [sequence], [seed], [encoding] ); | REFERENCE ( table, column, [sequence], [seed] );
INTEGER ( min, max, [sequence], [seed] ); INTEGER ( -10, 10, 1, 123456 );
min
is an integer, max
is an integer,
sequence
is an integer and seed
is an
integer.
REAL ( min, max, precision, [sequence], [seed] ); REAL ( 1.5, 1.8, 2, 1 );
min
is a number, max
is a number,
precision
is an integer that indicates the number of decimals
(should be less than 30), sequence
is an integer and
seed
is an integer.
DATE ( min, max, [sequence], [seed] ); DATE ( '2008-05-01', '2008-05-05', 0 );
min
is a string representing a date, max
is a
string representing a date, sequence
is an integer and
seed
is an integer.
TIME ( min, max, [sequence], [seed] ); TIME ( '00:30:00', '00:30:15', 0 );
min
is a string representing a time, max
is a
string representing a time, sequence
is an integer and
seed
is an integer.
DATETIME ( min, max, [sequence], [seed] ); DATETIME ( '2008-05-01 14:00:00', '2008-05-05 15:00:00', 1 );
min
is a string representing a timestamp, max
is a string representing a timestamp, sequence
is an integer
and seed
is an integer.
STRING ( min, max, [nb], [seed] ); STRING ( 10, 20, 5 );
min
is an integer representing the minimum length of a
word, max
is an integer representing the maximum length of a
word, nb
is an integer representing the number of words
(default: 1
) and seed
is an integer.
In the above example we generate 5 words (separated with a space) whose size is between 10 and 20 characters.
REGEX ( regex, [seed] ); REGEX ( '[a-z]{1,3}@[0-9]{3}' );
regex
is a string representing a simplified regular
expressions and seed
is an integer.
Simplified regular expressions are composed of:
Sets of possible characters like [a-z_.]
for characters
between a
and z
+ _
and
.
Single characters
It is possible to specify the minimum and maximum length of the preceding set or single character:
{min, max}
like {1,3}
which stands for
length between 1
and 3
{min}
like {3}
which stands for length of
3
Default (when nothing is specified) is length of 1
Note: be careful with spaces because 'a {3}'
means one
a
followed by three spaces because the 3
is about
the last character or set of characters which is a space in this
example.
If you need to use [
]
\
{
or }
, they must be escaped because they are
special characters. Remember to use double backslash:
'\\[{3}'
for three [
.
FILE ( path, [sequence], [seed], [encoding] ); FILE ( 'file.txt', 0, 54321, 'utf-8' );
path
is a string representing the path to a text file,
sequence
is an integer, seed
is an integer and
encoding
is a string representing the file character set
(default is system encoding).
This generates a random integer between 1 and the number of lines in the file and then returns that line. If the file does not exist then an exception is thrown.
encoding
supports the most known encoding like utf-8,
utf-16le, utf-16be, iso-8859-1, ...
REFERENCE ( table, column, [sequence], [seed] ); REFERENCE ( 'tab', 'col', 1 );
table
is a string representing a table, column
is a string representing a column of the table, sequence
is an
integer and seed
is an integer.
This is useful for generating data to put into foreign-key-constrained columns.