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# Bugzilla::DB

- NAME
- SYNOPSIS
- DESCRIPTION
- CONSTANTS
- CONNECTION
  - Functions
- ABSTRACT METHODS
  - Constructor
  - SQL Generation
- IMPLEMENTED METHODS
  - General Information Methods
  - Database Setup Methods
  - Schema Modification Methods
  - Schema Information Methods
  - Transaction Methods
- SUBCLASS HELPERS
- SEE ALSO

# NAME

Bugzilla::DB - Database access routines, using DBI

# SYNOPSIS

      # Obtain db handle
      use Bugzilla::DB;
      my $dbh = Bugzilla->dbh;

      # prepare a query using DB methods
      my $sth = $dbh->prepare("SELECT " .
                              $dbh->sql_date_format("creation_ts", "%Y%m%d") .
                              " FROM bugs WHERE bug_status != 'RESOLVED' " .
                              $dbh->sql_limit(1));

      # Execute the query
      $sth->execute;

      # Get the results
      my @result = $sth->fetchrow_array;

      # Schema Modification
      $dbh->bz_add_column($table, $name, \%definition, $init_value);
      $dbh->bz_add_index($table, $name, $definition);
      $dbh->bz_add_table($name);
      $dbh->bz_drop_index($table, $name);
      $dbh->bz_drop_table($name);
      $dbh->bz_alter_column($table, $name, \%new_def, $set_nulls_to);
      $dbh->bz_drop_column($table, $column);
      $dbh->bz_rename_column($table, $old_name, $new_name);

      # Schema Information
      my $column = $dbh->bz_column_info($table, $column);
      my $index  = $dbh->bz_index_info($table, $index);

# DESCRIPTION

Functions in this module allows creation of a database handle to connect to the Bugzilla database. This should never be done directly; all users should use the Bugzilla module to access the current `dbh` instead.

This module also contains methods extending the returned handle with functionality which is different between databases allowing for easy customization for particular database via inheritance. These methods should be always preffered over hard-coding SQL commands.

# CONSTANTS

Subclasses of Bugzilla::DB are required to define certain constants. These constants are required to be subroutines or "use constant" variables.

`BLOB_TYPE`

  The `\%attr` argument that must be passed to bind_param in order to correctly escape a `LONGBLOB` type.

`ISOLATION_LEVEL`

  The argument that this database should send to `SET TRANSACTION ISOLATION LEVEL` when starting a transaction. If you override this in a subclass, the isolation level you choose should be as strict as or more strict than the default isolation level defined in Bugzilla::DB.

# CONNECTION

A new database handle to the required database can be created using this module. This is normally done by the Bugzilla module, and so these routines should not be called from anywhere else.

## Functions

`connect_main`
  Description

    Function to connect to the main database, returning a new database handle.

  Params
    `$no_db_name` (optional) - If true, connect to the database server, but don't connect to a specific database. This is only used when creating a database. After you create the database, you should re-create a new Bugzilla::DB object without using this parameter.
  Returns

    New instance of the DB class

`connect_shadow`
  Description

    Function to connect to the shadow database, returning a new database handle. This routine `die`s if no shadow database is configured.

  Params (none)
  Returns

    A new instance of the DB class

`bz_check_requirements`
  Description

    Checks to make sure that you have the correct DBD and database version installed for the database that Bugzilla will be using. Prints a message and exits if you don't pass the requirements.

    If `$db_check` is false (from localconfig), we won't check the database version.

  Params
    `$output` - `true` if the function should display informational output about what it's doing, such as versions found.
  Returns (nothing)
`bz_create_database`
  Description

    Creates an empty database with the name `$db_name`, if that database doesn't already exist. Prints an error message and exits if we can't create the database.

  Params (none)
  Returns (nothing)
`_connect`
  Description

    Internal function, creates and returns a new, connected instance of the correct DB class. This routine `die`s if no driver is specified.

  Params
    `$driver` - name of the database driver to use
    `$host` - host running the database we are connecting to
    `$dbname` - name of the database to connect to
    `$port` - port the database is listening on
    `$sock` - socket the database is listening on
    `$user` - username used to log in to the database
    `$pass` - password used to log in to the database
  Returns

    A new instance of the DB class

`_handle_error`

  Function passed to the DBI::connect call for error handling. It shortens the error for printing.

`import`

  Overrides the standard import method to check that derived class implements all required abstract methods. Also calls original implementation in its super class.

# ABSTRACT METHODS

Note: Methods which can be implemented generically for all DBs are implemented in this module. If needed, they can be overridden with DB specific code. Methods which do not have standard implementation are abstract and must be implemented for all supported databases separately. To avoid confusion with standard DBI methods, all methods returning string with formatted SQL command have prefix `sql_`. All other methods have prefix `bz_`.

## Constructor

`new`
  Description

    Constructor. Abstract method, should be overridden by database specific code.

  Params
    `$user` - username used to log in to the database
    `$pass` - password used to log in to the database
    `$host` - host running the database we are connecting to
    `$dbname` - name of the database to connect to
    `$port` - port the database is listening on
    `$sock` - socket the database is listening on
  Returns

    A new instance of the DB class

  Note

    The constructor should create a DSN from the parameters provided and then call `db_new()` method of its super class to create a new class instance. See db_new description in this module. As per DBI documentation, all class variables must be prefixed with "private_". See DBI.

## SQL Generation

`sql_regexp`
  Description

    Outputs SQL regular expression operator for POSIX regex searches (case insensitive) in format suitable for a given database.

    Abstract method, should be overridden by database specific code.

  Params
    `$expr` - SQL expression for the text to be searched (scalar)
    `$pattern` - the regular expression to search for (scalar)
    `$nocheck` - true if the pattern should not be tested; false otherwise (boolean)
    `$real_pattern` - the real regular expression to search for. This argument is used when `$pattern` is a placeholder ('?').
  Returns

    Formatted SQL for regular expression search (e.g. REGEXP) (scalar)

`sql_not_regexp`
  Description

    Outputs SQL regular expression operator for negative POSIX regex searches (case insensitive) in format suitable for a given database.

    Abstract method, should be overridden by database specific code.

  Params

    Same as "sql_regexp".

  Returns

    Formatted SQL for negative regular expression search (e.g. NOT REGEXP) (scalar)

`sql_limit`
  Description

    Returns SQL syntax for limiting results to some number of rows with optional offset if not starting from the begining.

    Abstract method, should be overridden by database specific code.

  Params
    `$limit` - number of rows to return from query (scalar)
    `$offset` - number of rows to skip before counting (scalar)
  Returns

    Formatted SQL for limiting number of rows returned from query with optional offset (e.g. LIMIT 1, 1) (scalar)

`sql_from_days`
  Description

    Outputs SQL syntax for converting Julian days to date.

    Abstract method, should be overridden by database specific code.

  Params
    `$days` - days to convert to date
  Returns

    Formatted SQL for returning Julian days in dates. (scalar)

`sql_to_days`
  Description

    Outputs SQL syntax for converting date to Julian days.

    Abstract method, should be overridden by database specific code.

  Params
    `$date` - date to convert to days
  Returns

    Formatted SQL for returning date fields in Julian days. (scalar)

`sql_date_format`
  Description

    Outputs SQL syntax for formatting dates.

    Abstract method, should be overridden by database specific code.

  Params
    `$date` - date or name of date type column (scalar)
    `$format` - format string for date output (scalar) (`%Y` = year, four digits, `%y` = year, two digits, `%m` = month, `%d` = day, `%a` = weekday name, 3 letters, `%H` = hour 00-23, `%i` = minute, `%s` = second)
  Returns

    Formatted SQL for date formatting (scalar)

`sql_interval`
  Description

    Outputs proper SQL syntax for a time interval function.

    Abstract method, should be overridden by database specific code.

  Params
    `$interval` - the time interval requested (e.g. '30') (integer)
    `$units` - the units the interval is in (e.g. 'MINUTE') (string)
  Returns

    Formatted SQL for interval function (scalar)

`sql_position`
  Description

    Outputs proper SQL syntax determining position of a substring (fragment) withing a string (text). Note: if the substring or text are string constants, they must be properly quoted (e.g. "'pattern'").

    It searches for the string in a case-sensitive manner. If you want to do a case-insensitive search, use "sql_iposition".

  Params
    `$fragment` - the string fragment we are searching for (scalar)
    `$text` - the text to search (scalar)
  Returns

    Formatted SQL for substring search (scalar)

`sql_iposition`

  Just like "sql_position", but case-insensitive.

`sql_group_by`
  Description

    Outputs proper SQL syntax for grouping the result of a query.

    For ANSI SQL databases, we need to group by all columns we are querying for (except for columns used in aggregate functions). Some databases require (or even allow) to specify only one or few columns if the result is uniquely defined. For those databases, the default implementation needs to be overloaded.

  Params
    `$needed_columns` - string with comma separated list of columns we need to group by to get expected result (scalar)
    `$optional_columns` - string with comma separated list of all other columns we are querying for, but which are not in the required list.
  Returns

    Formatted SQL for row grouping (scalar)

`sql_string_concat`
  Description

    Returns SQL syntax for concatenating multiple strings (constants or values from table columns) together.

  Params
    `@params` - array of column names or strings to concatenate
  Returns

    Formatted SQL for concatenating specified strings

`sql_string_until`
  Description

    Returns SQL for truncating a string at the first occurrence of a certain substring.

  Params

    Note that both parameters need to be sql-quoted.

  `$string` The string we're truncating
  `$substring` The substring we're truncating at.
`sql_fulltext_search`
  Description

    Returns one or two SQL expressions for performing a full text search for specified text on a given column.

    If one value is returned, it is a numeric expression that indicates a match with a positive value and a non-match with zero. In this case, the DB must support casting numeric expresions to booleans.

    If the DB does not support casting numeric expresions to booleans, then the first value is a boolean expression that indicates the presence of a match, and the second value is a numeric expression that can be used for ranking.

    There is a ANSI SQL version of this method implemented using LIKE operator, but it's not a real full text search. DB specific modules should override this, as this generic implementation will be always much slower. This generic implementation returns 'relevance' as 0 for no match, or 1 for a match.

  Params
    `$column` - name of column to search (scalar)
    `$text` - text to search for (scalar)
  Returns

    Formatted SQL for full text search

`sql_istrcmp`
  Description

    Returns SQL for a case-insensitive string comparison.

  Params
    `$left` - What should be on the left-hand-side of the operation.
    `$right` - What should be on the right-hand-side of the operation.
    `$op` (optional) - What the operation is. Should be a valid ANSI SQL comparison operator, such as `=`, `<`, `LIKE`, etc. Defaults to `=` if not specified.
  Returns

    A SQL statement that will run the comparison in a case-insensitive fashion.

  Note

    Uses "sql_istring", so it has the same performance concerns. Try to avoid using this function unless absolutely necessary.

    Subclass Implementors: Override sql_istring instead of this function, most of the time (this function uses sql_istring).

`sql_istring`
  Description

    Returns SQL syntax "preparing" a string or text column for case-insensitive comparison.

  Params
    `$string` - string to convert (scalar)
  Returns

    Formatted SQL making the string case insensitive.

  Note

    The default implementation simply calls LOWER on the parameter. If this is used to search on a text column with index, the index will not be usually used unless it was created as LOWER(column).

`sql_in`
  Description

    Returns SQL syntax for the `IN ()` operator.

    Only necessary where an `IN` clause can have more than 1000 items.

  Params
    `$column_name` - Column name (e.g. `bug_id`)
    `$in_list_ref` - an arrayref containing values for `IN ()`
  Returns

    Formatted SQL for the `IN` operator.

# IMPLEMENTED METHODS

These methods are implemented in Bugzilla::DB, and only need to be implemented in subclasses if you need to override them for database-compatibility reasons.

## General Information Methods

These methods return information about data in the database.

`bz_last_key`
  Description

    Returns the last serial number, usually from a previous INSERT.

    Must be executed directly following the relevant INSERT. This base implementation uses "last_insert_id" in DBI. If the DBD supports it, it is the preffered way to obtain the last serial index. If it is not supported, the DB-specific code needs to override this function.

  Params
    `$table` - name of table containing serial column (scalar)
    `$column` - name of column containing serial data type (scalar)
  Returns

    Last inserted ID (scalar)

## Database Setup Methods

These methods are used by the Bugzilla installation programs to set up the database.

`bz_populate_enum_tables`
  Description

    For an upgrade or an initial installation, populates the tables that hold the legal values for the old "enum" fields: `bug_severity`, `resolution`, etc. Prints out information if it inserts anything into the DB.

  Params (none)
  Returns (nothing)

## Schema Modification Methods

These methods modify the current Bugzilla Schema.

Where a parameter says "Abstract index/column definition", it returns/takes information in the formats defined for indexes and columns in `Bugzilla::DB::Schema::ABSTRACT_SCHEMA`.

`bz_add_column`
  Description

    Adds a new column to a table in the database. Prints out a brief statement that it did so, to stdout. Note that you cannot add a NOT NULL column that has no default -- the database won't know what to set all the NULL values to.

  Params
    `$table` - the table where the column is being added
    `$name` - the name of the new column
    `\%definition` - Abstract column definition for the new column
    `$init_value` (optional) - An initial value to set the column to. Required if your column is NOT NULL and has no DEFAULT set.
  Returns (nothing)
`bz_add_index`
  Description

    Adds a new index to a table in the database. Prints out a brief statement that it did so, to stdout. If the index already exists, we will do nothing.

  Params
    `$table` - The table the new index is on.
    `$name` - A name for the new index.
    `$definition` - An abstract index definition. Either a hashref or an arrayref.
  Returns (nothing)
`bz_add_table`
  Description

    Creates a new table in the database, based on the definition for that table in the abstract schema.

    Note that unlike the other 'add' functions, this does not take a definition, but always creates the table as it exists in "ABSTRACT_SCHEMA" in Bugzilla::DB::Schema.

    If a table with that name already exists, then this function returns silently.

  Params
    `$name` - The name of the table you want to create.
  Returns (nothing)
`bz_drop_index`
  Description

    Removes an index from the database. Prints out a brief statement that it did so, to stdout. If the index doesn't exist, we do nothing.

  Params
    `$table` - The table that the index is on.
    `$name` - The name of the index that you want to drop.
  Returns (nothing)
`bz_drop_table`
  Description

    Drops a table from the database. If the table doesn't exist, we just return silently.

  Params
    `$name` - The name of the table to drop.
  Returns (nothing)
`bz_alter_column`
  Description

    Changes the data type of a column in a table. Prints out the changes being made to stdout. If the new type is the same as the old type, the function returns without changing anything.

  Params
    `$table` - the table where the column is
    `$name` - the name of the column you want to change
    `\%new_def` - An abstract column definition for the new data type of the columm
    `$set_nulls_to` (Optional) - If you are changing the column to be NOT NULL, you probably also want to set any existing NULL columns to a particular value. Specify that value here. NOTE: The value should not already be SQL-quoted.
  Returns (nothing)
`bz_drop_column`
  Description

    Removes a column from a database table. If the column doesn't exist, we return without doing anything. If we do anything, we print a short message to `stdout` about the change.

  Params
    `$table` - The table where the column is
    `$column` - The name of the column you want to drop
  Returns (nothing)
`bz_rename_column`
  Description

    Renames a column in a database table. If the `$old_name` column doesn't exist, we return without doing anything. If `$old_name` and `$new_name` both already exist in the table specified, we fail.

  Params
    `$table` - The name of the table containing the column that you want to rename
    `$old_name` - The current name of the column that you want to rename
    `$new_name` - The new name of the column
  Returns (nothing)
`bz_rename_table`
  Description

    Renames a table in the database. Does nothing if the table doesn't exist.

    Throws an error if the old table exists and there is already a table with the new name.

  Params
    `$old_name` - The current name of the table.
    `$new_name` - What you're renaming the table to.
  Returns (nothing)

## Schema Information Methods

These methods return information about the current Bugzilla database schema, as it currently exists on the disk.

Where a parameter says "Abstract index/column definition", it returns/takes information in the formats defined for indexes and columns for "ABSTRACT_SCHEMA" in Bugzilla::DB::Schema.

`bz_column_info`
  Description

    Get abstract column definition.

  Params
    `$table` - The name of the table the column is in.
    `$column` - The name of the column.
  Returns

    An abstract column definition for that column. If the table or column does not exist, we return `undef`.

`bz_index_info`
  Description

    Get abstract index definition.

  Params
    `$table` - The table the index is on.
    `$index` - The name of the index.
  Returns

    An abstract index definition for that index, always in hashref format. The hashref will always contain the `TYPE` element, but it will be an empty string if it's just a normal index.

    If the index does not exist, we return `undef`.

## Transaction Methods

These methods deal with the starting and stopping of transactions in the database.

`bz_in_transaction`

  Returns `1` if we are currently in the middle of an uncommitted transaction, `0` otherwise.

`bz_start_transaction`

  Starts a transaction.

  It is OK to call `bz_start_transaction` when you are already inside of a transaction. However, you must call "bz_commit_transaction" as many times as you called `bz_start_transaction`, in order for your transaction to actually commit.

  Bugzilla uses `REPEATABLE READ` transactions.

  Returns nothing and takes no parameters.

`bz_commit_transaction`

  Ends a transaction, commiting all changes. Returns nothing and takes no parameters.

`bz_rollback_transaction`

  Ends a transaction, rolling back all changes. Returns nothing and takes no parameters.

# SUBCLASS HELPERS

Methods in this class are intended to be used by subclasses to help them with their functions.

`db_new`
  Description

    Constructor

  Params
    `$dsn` - database connection string
    `$user` - username used to log in to the database
    `$pass` - password used to log in to the database
    `\%override_attrs` - set of attributes for DB connection (optional). You only have to set attributes that you want to be different from the default attributes set inside of `db_new`.
  Returns

    A new instance of the DB class

  Note

    The name of this constructor is not `new`, as that would make our check for implementation of `new` by derived class useless.

# SEE ALSO

DBI

"DB_MODULE" in Bugzilla::Constants

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