/ 
SQL-SplitStatement-1.00009
River stage two • 6 direct dependents • 31 total dependents
/ SQL::SplitStatement

NAME

SQL::SplitStatement - Split any SQL code into atomic statements

VERSION

version 1.00009

SYNOPSIS

# Multiple SQL statements in a single string
my $sql_code = <<'SQL';
CREATE TABLE parent(a, b, c   , d    );
CREATE TABLE child (x, y, "w;", "z;z");
/* C-style comment; */
CREATE TRIGGER "check;delete;parent;" BEFORE DELETE ON parent WHEN
    EXISTS (SELECT 1 FROM child WHERE old.a = x AND old.b = y)
BEGIN
    SELECT RAISE(ABORT, 'constraint failed;'); -- Inline SQL comment
END;
-- Standalone SQL; comment; with semicolons;
INSERT INTO parent (a, b, c, d) VALUES ('pippo;', 'pluto;', NULL, NULL);
SQL

use SQL::SplitStatement;

my $sql_splitter = SQL::SplitStatement->new;
my @statements = $sql_splitter->split($sql_code);

# @statements now is:
#
# (
#     'CREATE TABLE parent(a, b, c   , d    )',
#     'CREATE TABLE child (x, y, "w;", "z;z")',
#     'CREATE TRIGGER "check;delete;parent;" BEFORE DELETE ON parent WHEN
#     EXISTS (SELECT 1 FROM child WHERE old.a = x AND old.b = y)
# BEGIN
#     SELECT RAISE(ABORT, \'constraint failed;\');
# END',
#     'INSERT INTO parent (a, b, c, d) VALUES (\'pippo;\', \'pluto;\', NULL, NULL)'
# )

DESCRIPTION

This is a simple module which tries to split any SQL code, even including non-standard extensions (for the details see the "SUPPORTED DBMSs" section below), into the atomic statements it is composed of.

The logic used to split the SQL code is more sophisticated than a raw split on the ; (semicolon) character: first, various different statement terminator tokens are recognized (see below for the list), then this module is able to correctly handle the presence of said tokens inside identifiers, values, comments, BEGIN ... END blocks (even nested), dollar-quoted strings, MySQL custom DELIMITERs, procedural code etc., as (partially) exemplified in the "SYNOPSIS" above.

Consider however that this is by no means a validating parser (technically speaking, it's just a context-sensitive tokenizer). It should rather be seen as an in-progress heuristic approach, which will gradually improve as test cases will be reported. This also means that, except for the "LIMITATIONS" detailed below, there is no known (to the author) SQL code the most current release of this module can't correctly split.

The test suite bundled with the distribution (which now includes the popular Sakila and Pagila sample db schemata, as detailed in the "SHOWCASE" section below) should give you an idea of the capabilities of this module

If your atomic statements are to be fed to a DBMS, you are encouraged to use DBIx::MultiStatementDo instead, which uses this module and also (optionally) offers automatic transactions support, so that you'll have the all-or-nothing behavior you would probably want.

METHODS

new

  • SQL::SplitStatement->new( %options )

  • SQL::SplitStatement->new( \%options )

It creates and returns a new SQL::SplitStatement object. It accepts its options either as a hash or a hashref.

new takes the following Boolean options, which for documentation purposes can be grouped in two sets: "Formatting Options" and "DBMSs Specific Options".

Formatting Options

  • keep_terminators

    A Boolean option which causes, when set to a false value (which is the default), the trailing terminator token to be discarded in the returned atomic statements. When set to a true value, the terminators are kept instead.

    The possible terminators (which are treated as such depending on the context) are:

    • ; (the semicolon character);

    • any string defined by the MySQL DELIMITER command;

    • an ; followed by an / (forward-slash character) on its own line;

    • an ; followed by an . (dot character) on its own line, followed by an / on its own line;

    • an / on its own line regardless of the preceding characters (only if the slash_terminates option, explained below, is set).

    The multi-line terminators above are always treated as a single token, that is they are discarded (or returned) as a whole (regardless of the slash_terminates option value).

    If your statements are to be fed to a DBMS, you are advised to keep this option to its default (false) value, since some drivers/DBMSs don't want the terminator to be present at the end of the (single) statement.

    (Note that the last, possibly empty, statement of a given SQL text, never has a trailing terminator. See below for an example.)

  • keep_terminator

    An alias for the the keep_terminators option explained above. Note that if keep_terminators and keep_terminator are both passed to new, an exception is thrown.

  • keep_extra_spaces

    A Boolean option which causes, when set to a false value (which is the default), the spaces (\s) around the statements to be trimmed. When set to a true value, these spaces are kept instead.

    When keep_terminators is set to false as well, the terminator is discarded first (regardless of the spaces around it) and the trailing spaces are trimmed then. This ensures that if keep_extra_spaces is set to false, the returned statements will never have trailing (nor leading) spaces, regardless of the keep_terminators value.

  • keep_comments

    A Boolean option which causes, when set to a false value (which is the default), the comments to be discarded in the returned statements. When set to a true value, they are kept with the statements instead.

    Both SQL and multi-line C-style comments are recognized.

    When kept, each comment is returned in the same string with the atomic statement it belongs to. A comment belongs to a statement if it appears, in the original SQL code, before the end of that statement and after the terminator of the previous statement (if it exists), as shown in this pseudo-SQL snippet:

    /* This comment
will be returned
together with statement1 */

<statement1>; -- This will go with statement2
              -- (note the semicolon which closes statement1)

<statement2>
-- This with statement2 as well

  • keep_empty_statements

    A Boolean option which causes, when set to a false value (which is the default), the empty statements to be discarded. When set to a true value, the empty statements are returned instead.

    A statement is considered empty when it contains no characters other than the terminator and space characters (\s).

    A statement composed solely of comments is not recognized as empty and may therefore be returned even when keep_empty_statements is false. To avoid this, it is sufficient to leave keep_comments to false as well.

    Note instead that an empty statement is recognized as such regardless of the value of the options keep_terminators and keep_extra_spaces.

These options are basically to be kept to their default (false) values, especially if the atomic statements are to be given to a DBMS.

They are intended mainly for cosmetic reasons, or if you want to count by how many atomic statements, including the empty ones, your original SQL code was composed of.

Another situation where they are useful (in the general case necessary, really), is when you want to retain the ability to verbatim rebuild the original SQL string from the returned statements:

my $verbatim_splitter = SQL::SplitStatement->new(
    keep_terminators      => 1,
    keep_extra_spaces     => 1,
    keep_comments         => 1,
    keep_empty_statements => 1
);

my @verbatim_statements = $verbatim_splitter->split($sql_string);

$sql_string eq join '', @verbatim_statements; # Always true, given the constructor above.

Other than this, again, you are recommended to stick with the defaults.

DBMSs Specific Options

The same syntactic structure can have different semantics across different SQL dialects, so sometimes it is necessary to help the parser to make the right decision. This is the function of these options.

  • slash_terminates

    A Boolean option which causes, when set to a true value (which is the default), a / (forward-slash) on its own line, even without a preceding semicolon, to be admitted as a (possible) terminator.

    If set to false, a forward-slash on its own line is treated as a statement terminator only if preceded by a semicolon or by a dot and a semicolon.

    If you are dealing with Oracle's SQL, you should let this option set, since a slash (alone, without a preceding semicolon) is often used as a terminator, as it is permitted by SQL*Plus (on non-block statements).

    With SQL dialects other than Oracle, there is the (theoretical) possibility that a slash on its own line can pass the additional checks and be considered a terminator (while it shouldn't). This chance should be really tiny (it has never been observed in real world code indeed). Though negligible, by setting this option to false that risk can anyway be ruled out.

split

  • $sql_splitter->split( $sql_string )

This is the method which actually splits the SQL code into its atomic components.

It returns a list containing the atomic statements, in the same order they appear in the original SQL code. The atomic statements are returned according to the options explained above.

Note that, as mentioned above, an SQL string which terminates with a terminator token (for example a semicolon), contains a trailing empty statement: this is correct and it is treated accordingly (if keep_empty_statements is set to a true value):

my $sql_splitter = SQL::SplitStatement->new(
    keep_empty_statements => 1
);

my @statements = $sql_splitter->split( 'SELECT 1;' );

print 'The SQL code contains ' . Scalar(@statements) . ' statements.';
# The SQL code contains 2 statements.

split_with_placeholders

  • $sql_splitter->split_with_placeholders( $sql_string )

It works exactly as the split method explained above, except that it returns also a list of integers, each of which is the number of the unnamed placeholders contained in the corresponding atomic statement.

More precisely, its return value is a list of two elements, the first of which is a reference to the list of the atomic statements exactly as returned by the split method, while the second is a reference to the list of the number of placeholders as explained above.

Here is an example:

# 4 statements (valid SQLite SQL)
my $sql_code = <<'SQL';
CREATE TABLE state (id, name);
INSERT INTO  state (id, name) VALUES (?, ?);
CREATE TABLE city  (id, name, state_id);
INSERT INTO  city  (id, name, state_id) VALUES (?, ?, ?)
SQL

my $splitter = SQL::SplitStatement->new;

my ( $statements, $placeholders )
    = $splitter->split_with_placeholders( $sql_code );

# $placeholders now is: [0, 2, 0, 3]

where the returned $placeholders list(ref) is to be read as follows: the first statement contains 0 placeholders, the second 2, the third 0 and the fourth 3.

The recognized placeholders are:

  • question mark placeholders, represented by the ? character;

  • dollar sign numbered placeholders, represented by the $1, $2, ..., $n strings;

  • named parameters, such as :foo, :bar, :baz etc.

keep_terminators

  • $sql_splitter->keep_terminators

  • $sql_splitter->keep_terminators( $boolean )

    Getter/setter method for the keep_terminators option explained above.

keep_terminator

An alias for the keep_terminators method explained above.

keep_extra_spaces

  • $sql_splitter->keep_extra_spaces

  • $sql_splitter->keep_extra_spaces( $boolean )

    Getter/setter method for the keep_extra_spaces option explained above.

keep_comments

  • $sql_splitter->keep_comments

  • $sql_splitter->keep_comments( $boolean )

    Getter/setter method for the keep_comments option explained above.

keep_empty_statements

  • $sql_splitter->keep_empty_statements

  • $sql_splitter->keep_empty_statements( $boolean )

    Getter/setter method for the keep_empty_statements option explained above.

slash_terminates

  • $sql_splitter->slash_terminates

  • $sql_splitter->slash_terminates( $boolean )

    Getter/setter method for the slash_terminates option explained above.

SUPPORTED DBMSs

SQL::SplitStatement aims to cover the widest possible range of DBMSs, SQL dialects and extensions (even proprietary), in a (nearly) fully transparent way for the user.

Currently it has been tested mainly on SQLite, PostgreSQL, MySQL and Oracle.

Procedural Extensions

Procedural code is by far the most complex to handle.

Currently any block of code which start with DECLARE, CREATE or CALL is correctly recognized, as well as anonymous BEGIN ... END blocks, dollar quoted blocks and blocks delimited by a DELIMITER-defined custom terminator, therefore a wide range of procedural extensions should be handled correctly. However, only PL/SQL, PL/PgSQL and MySQL code has been tested so far.

If you need also other procedural languages to be recognized, please let me know (possibly with some test cases).

LIMITATIONS

Bound to be plenty, given the heuristic nature of this module (and its ambitious goals). However, no limitations are currently known.

Please report any problematic test case.

Non-limitations

To be split correctly, the given input must, in general, be syntactically valid SQL. For example, an unbalanced BEGIN or a misspelled keyword could, under certain circumstances, confuse the parser and make it trip over the next statement terminator, thus returning non-split statements. This should not be a problem though, as the original (invalid) SQL code would have been unusable anyway (remember that this is NOT a validating parser!)

SHOWCASE

To test the capabilities of this module, you can run it (or rather run sql-split) on the files t/data/sakila-schema.sql and t/data/pagila-schema.sql included in the distribution, which contain two quite large and complex real world sample db schemata, for MySQL and PostgreSQL respectively.

For more information:

DEPENDENCIES

SQL::SplitStatement depends on the following modules:

AUTHOR

Emanuele Zeppieri, <emazep@cpan.org>

BUGS

No known bugs.

Please report any bugs or feature requests to bug-sql-SplitStatement at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=SQL-SplitStatement. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command:

perldoc SQL::SplitStatement

You can also look for information at:

ACKNOWLEDGEMENTS

Igor Sutton for his excellent SQL::Tokenizer, which made writing this module a joke.

SEE ALSO

LICENSE AND COPYRIGHT

Copyright 2010-2011 Emanuele Zeppieri.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation, or the Artistic License.

See http://dev.perl.org/licenses/ for more information.