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Easily load a database table from a dataset

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README.pod

NAME

DBIx::TableLoader - Easily load a database table from a data set

VERSION

version 1.100

SYNOPSIS

  my $dbh = DBI->connect(@connection_args);

  DBIx::TableLoader->new(dbh => $dbh, data => $data)->load();

  # interact with new database table full of data in $dbh

DESCRIPTION

This module tries to provide a fast and simple (but very configurable) interface for taking a set of data and loading it into a database table.

Common uses would be to take data from a file (like a CSV) and load it into a SQLite table. (For that specific case see DBIx::TableLoader::CSV.)

In most cases simply calling load() is sufficient, but all methods are documented below for completeness.

METHODS

new

Create a new instance. Accepts a hash or hashref of options.

This module is very configurable but tries to use good defaults in the hopes that you won't need to configure too much in most cases.

Most likely needed options:

  • dbh - A database handle as returned by DBI->connect()
  • data - An arrayref of arrayrefs of data (which will be the input records)

See "OPTIONS" for the full list.

base_defaults

Returns a hashref of the options defined by the base class and their default values.

defaults

Returns a hashref of additional options defined by a subclass.

columns

  my $columns = $loader->columns;
  # [ ['column1', 'data type'], ['column two', 'data type'] ]

Returns an arrayref of the columns. Each element is an arrayref of column name and column data type.

column_names

  my $column_names = $loader->column_names;
  # ['column1', 'column two']

Returns an arrayref of the column names.

create

Executes a CREATE TABLE SQL statement on the database handle.

create_prefix

Generates the opening of the CREATE TABLE statement (everything before the column specifications).

Defaults to "CREATE $table_type TABLE $quoted_name (".

create_sql

Generates the SQL for the CREATE TABLE statement by concatenating "create_prefix", the column definitions, and "create_suffix".

Can be overridden in the constructor.

create_suffix

Generates the closing of the CREATE TABLE statement (everything after the column specifications).

Defaults to ")".

default_name

Returns the default (base) name for the table.

This is mostly for subclasses where a useful table name can be determined from the input (like a filename). In this module it defaults to 'data'.

This gets concatenated together with "name_prefix" and "name_suffix" in "name".

default_column_type

Columns that have not been given an explicit data type will be defined using the default_column_type.

You can pass a value explicitly to the constructor, or it will try to determine an appropriate (string) type based on the database driver (using "default_sql_data_type").

If all else fails it will default to text (which works for SQLite, PostgreSQL, MySQL, and some others).

default_sql_data_type

Passed to "type_info" in DBI to query the database driver for an appropriate default column type.

Defaults to DBI::SQL_LONGVARCHAR.

determine_column_types

This method goes through the columns and converts any scalar column name to an arrayref of column name and default_column_type. It modifies itself and returns nothing. It is called automatically from the constructor.

drop

Execute the DROP TABLE statement on the database handle.

drop_prefix

Returns the portion of the SQL statement before the table name.

Defaults to DROP TABLE.

drop_sql

Generates the SQL for the DROP TABLE statement by concatenating "drop_prefix", "quoted_name", and "drop_suffix".

Alternatively drop_sql can be set in the constructor if you need something more complex.

drop_suffix

Returns the portion of the SQL statement after the table name.

Nothing by default.

get_raw_row

Subclasses will override this method according to the input data format.

This is called from "get_row" to retrieve the next row of raw data.

It should return undef when there are no more rows.

get_row

  my $row = $loader->get_row();

Returns a single row of data at a time (as an arrayref). This method will be called repeatedly until it returns undef. The returned arrayref will be flattened and passed to "execute" in DBI.

handle_invalid_row

This is called from "get_row" when a row is determined to be invalid (when "validate_row" throws an error).

If handle_invalid_row was not specified in the constructor this method is a no-op: the original row will be returned (and eventually passed to "execute" in DBI).

Possible values for the handle_invalid_row option:

  • die - Calls die() with the error message
  • warn - Calls warn() with the error message and returns the row unmodified
  • code ref

    If it's a subroutine reference it is called as a method, receiving the loader object, the error message, and the row:

      $handler->($loader, $error, $row);

    The handler should either die to cease processing, return false to skip this row and get the next one, or return a (possibly modified) row that will be passed to "execute" in DBI.

    This allows you to, for example, write to a log when a bad row is found without aborting your transaction:

      handle_invalid_row => sub {
        my ($self, $error, $row) = @_;
        $logger->log(['Bad row: %s: %s', $error, $row]);
        return; # return false to skip this row and move to the next one
      }

insert_sql

Generate the INSERT SQL statement that will be passed to "prepare" in DBI.

insert_all

Execute an INSERT statement on the database handle for each row of data. It will call "prepare" in DBI using "insert_sql" and then call "execute" in DBI once for each row returned by "get_row".

load

  my $number_of_rows = $loader->load();

Load data into database table. This is a wrapper that does the most commonly needed things in a single method call. If the transaction setting is true (default) the actions will be wrapped in a transaction.

Returns the number of rows inserted.

name

Returns the full table name (concatenation of name_prefix, name, and name_suffix).

prepare_data

This method is called from "new" after the object is blessed (obviously). Any preparation work specific to the type of data should be done here.

This is mostly a hook for subclasses and does very little in this module.

quoted_name

Returns the full, quoted table name. Passes catalog, schema, and name attributes to "quote_identifier" in DBI.

quoted_column_names

  my $quoted_names = $loader->quoted_column_names();
  # ['"column1"', '"column two"']

Returns an arrayref of column names quoted by the database driver.

validate_row

Called from "get_row" to check that the provided row is valid.

It may die for any error which will be caught in "get_row" and the error will be passed to "handle_invalid_row".

The return value works like that of "handle_invalid_row": On success, the valid row (possibly modified) should be returned. If a false value is returned "get_row" will attempt to get another row.

Currently this only checks that the number of fields in the row matches the number of columns expected, however other checks may be added in the future. Subclasses can overwrite this to define their own validations (though calling the original (superclass method) is recommended).

OPTIONS

This module is very [excessively] configurable. In most cases the default values will be sufficient, but you should be able to customize the object to fit your needs.

Frequently Used Options:

  • columns - Arrayref of column definitions

    Each element can be an arrayref of column name and data type or just a string for the column name and "default_column_type" will be used. If not passed in the first row of data will be assumed to be column names.

      columns => ['first_name', 'last_name', ['last_seen', 'date']]
  • dbh - A database handle as returned by DBI->connect()

    This module probably isn't useful without one.

  • data - An arrayref of arrayrefs of data to populate the table;

    Subclasses may define more appropriate options and ignore this parameter. If you're using this base class, you'll probably need this (unless you provide your own get_row coderef).

      data => [ ['polar', 'bear', '2010-08-15'], ['blue', 'duck', '2009-07-30'] ]

Less common options that are available when you desire extra tweaking power:

  • create - Boolean; Whether or not to perform the CREATE TABLE statement

    Defaults to true.

  • default_column_type - Default data type for each column

    This will be used for each column that does not explicitly define a data type. The default will be determined from the database driver using default_sql_data_type. See "default_column_type".

      default_column_type => 'CHAR(50)'
  • drop - Boolean to execute a DROP TABLE statement before CREATE TABLE

    Defaults to false. Set it to true if the named table already exists and you want to recreate it.

  • get_row - A sub (coderef) that will override "get_raw_row"

    You can use this if your input data is in a different format than the module expects (to split a string into an arrayref, for instance). This is called like a method (the object will be $_[0]). The return value will be passed to map_rows if both are present.

      # each record is a line from a log file;
      # use the m// operator in list context to capture desired fields
      get_row => sub { my $s = <$io>; [ $s =~ m/^(\d+)\s+"([^"]+)"\s+(\S+)$/ ] }

    NOTE: If you use get_row and don't pass data you will probably want to pass columns (otherwise columns will be taken from the first call to get_row).

  • grep_rows - A sub (coderef) to determine if a row should be used or skipped

    Named after the built in grep function. It will receive the row as an arrayref in $_[0]. (The row will also be available in $_ for consistency with the built in grep.) The object will be passed as $_[1] in case you want it. If it returns a true value the row will be used. If it returns false the next row will be fetched and the process will repeat (until all rows have been exhausted).

      grep_rows => sub { $_->[1] =~ /something/ } # accept the row if it matches
    
      grep_rows => sub { my ($row, $obj) = @_; do_something(); } # 2 variables
  • handle_invalid_row - How to handle invalid rows.

    Can be die, warn, or a sub (coderef). See "handle_invalid_row" for more details. Default is to ignore (in which case DBI will likely error).

  • map_rows - A sub (coderef) to filter/mangle a row before use

    Named after the built in map function. It will receive the row as an arrayref in $_[0]. (The row will also be available in $_ for consistency with the built in map.) The object will be passed as $_[1] in case you want it. It should return an arrayref (which will be used as the row).

      map_rows => sub { [ map { uc $_ } @$_ ] } # uppercase all the fields
    
      map_rows => sub { my ($row, $obj) = @_; do_something(); } # 2 variables
  • name - Table name

    Defaults to 'data'. Subclasses may provide a more useful default.

  • table_type - String that will go before TABLE in "create_prefix"

    A useful value might be TEMPORARY or TEMP. This is probably database driver dependent, so use an appropriate value.

  • transaction - Boolean

    All the operations in "load" will be wrapped in a transaction by default. Set this option to false to disable this.

Options that will seldom be necessary but are available for completeness and/or consistency:

  • catalog - Table catalog

    Passed to "quote_identifier" in DBI to get the full, quoted table name. None by default.

  • create_prefix - The opening of the SQL statement

    See "create_prefix". Overwrite if you need something more complex.

  • create_sql - The CREATE TABLE statement

    See "create_sql". Overwrite if you need something more complex.

  • create_suffix - The closing of the SQL statement

    See "create_suffix". Overwrite if you need something more complex.

  • default_sql_data_type - Default SQL standard data type

    If default_column_type is not supplied it will be determined by asking the database driver for a type corresponding to DBI::SQL_LONGVARCHAR. Alternate values can be passed (DBI::SQL_VARCHAR() for instance). See "default_sql_data_type".

  • drop_prefix - The opening of the SQL statement

    See "drop_prefix". Overwrite if you need something more complex.

  • drop_sql - The DROP TABLE statement

    Will be constructed if not provided. See "drop_sql".

  • drop_suffix - The closing of the SQL statement

    See "drop_suffix". Overwrite if you need something more complex.

  • name_prefix - String prepended to table name

    Probably mostly useful in subclasses where name is determined automatically.

  • name_suffix - String appended to table name

    Probably mostly useful in subclasses where name is determined automatically.

  • quoted_name - Full table name, properly quoted

    Only necessary if you need something more complicated than $dbh->quote_identifier($catalog, $schema, $table) (see "quote_identifier" in DBI).

  • schema - Table schema

    Passed to "quote_identifier" in DBI to get the full, quoted table name. None by default.

SUBCLASSING

This module was designed to be subclassed for use with specific data input formats.

DBIx::TableLoader::CSV is a prime example. It is the entire reason this base module was designed.

Subclasses will likely want to override the following methods:

  • "defaults" - a hashref of additional acceptable options (and default values)
  • "default_name" - if you can determine a good default name from the input
  • "get_raw_row" - to return the next row of data
  • "prepare_data" - to initialize your object/data (open the file, etc.)

Be sure to check out the code for DBIx::TableLoader::CSV. Also see a very simple example in t/subclass.t.

RATIONALE

It seemed frequent that I would find a data set that was difficult to view/analyze (CSV, log file, etc.) and would prefer to load it into a database for its powerful, familiar processing abilities.

I once chose to use MySQL because its built in LOAD DATA command read the malformed CSV I was given and the .import command in SQLite did not.

I wrote this module so that I'd never have to make such a choice again. I wanted to be able to use the power of Text::CSV to make sure I could take any CSV I ever got and load it into SQLite easily.

I tried to make this module a base class to be able to handle various formats.

TODO

This is more of a list of ideas than features that are planned.

  • Allow a custom column name transformation sub to be passed in
  • Use "decamelize" in String::CamelCase by default?
  • Allow extra columns (like id) to be added and/or generated
  • Option to scan the data to guess appropriate data types for each column
  • Make a SQLite function so that you could call this from a dbish command line?
  • Allow UPDATE statements and specify the key columns (for the WHERE clause)

SEE ALSO

SUPPORT

Perldoc

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

  perldoc DBIx::TableLoader

Websites

The following websites have more information about this module, and may be of help to you. As always, in addition to those websites please use your favorite search engine to discover more resources.

Bugs / Feature Requests

Please report any bugs or feature requests by email to bug-dbix-tableloader at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DBIx-TableLoader. You will be automatically notified of any progress on the request by the system.

Source Code

https://github.com/rwstauner/DBIx-TableLoader

  git clone https://github.com/rwstauner/DBIx-TableLoader.git

AUTHOR

Randy Stauner <rwstauner@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2011 by Randy Stauner.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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