Stefan Reddig > DBD-Ingres > DBD::Ingres

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Module Version: 0.53   Source  

NAME ^

DBD::Ingres - DBI driver for Ingres database systems

SYNOPSIS ^

    $dbh = DBI->connect("DBI:Ingres:$dbname", $user, $options, {AutoCommit=>0})
    $sth = $dbh->prepare($statement)
    $sth = $dbh->prepare($statement, {ing_readonly=>1})
    $sth->execute
    @row = $sth->fetchrow
    $sth->finish
    $dbh->commit
    $dbh->rollback
    $dbh->disconnect
    ...and many more

DESCRIPTION ^

DBD::Ingres is a database driver for the perl DBI system that allows access to Ingres databases. It is built on top of the standard DBI extension and implements the methods that DBI requires.

This document describes the differences between the "generic" DBD and DBD::Ingres.

EXTENSIONS/CHANGES ^

Connect

  DBI->connect("DBI:Ingres:dbname[;options]");
  DBI->connect("DBI:Ingres:dbname[;options]", user [, password]);
  DBI->connect("DBI:Ingres:dbname[;options]", user [, password], \%attr);

To use DBD::Ingres call connect specifying a datasource option beginning with "DBI:Ingres:", followed by the database instance name and optionally a semi-colon followed by any Ingres connect options.

Options must be given exactly as they would be given in an ESQL-connect statement, i.e., separated by blanks.

The connect call will result in a connect statement like:

  CONNECT dbname IDENTIFIED BY user PASSWORD password OPTIONS=options

E.g.,

and so on.

AutoCommit Defaults to ON

Important: The DBI spec defines that AutoCommit is ON after connect. This is the opposite of the normal Ingres default (autocommit OFF).

To reflect this behavior in your code, it is recommended that the connect call ends with the attributes { AutoCommit => 0 }.

Returned Types

The DBI docs state that:

This is not the case for Ingres.

Data is returned as it would be to an embedded C program:

This does not cause loss of precision, because the Ingres API uses these types to return the data anyway.

get_dbevent

This non-DBI method calls GET DBEVENT and INQUIRE_INGRES to fetch a pending database event. If called without argument a blocking GET DBEVENT WITH WAIT is called. A numeric argument results in a call to GET DBEVENT WITH WAIT= :seconds.

In a second step INQUIRE_INGRES is called to fetch the related information, wich is returned as a reference to a hash with keys name, database, text, owner and time. The values are the dbevent* values received from Ingres. If no event was fetched, undef is returned. See t/event.t for an example of usage.

  $event_ref = $dbh->func(10, 'get_dbevent')     # wait 10 secs at most
  $event_ref = $dbh->func('get_dbevent')         # blocks

  for (keys %$event_ref) {
    printf "%-20s = '%s'\n", $_, $event_ref->{$_};
  }

do

$dbh->do is implemented as a call to 'EXECUTE IMMEDIATE' with all the limitations that this implies. An exception to that are the DML statements INSERT, DELETE and UPDATE. For them, a call to PREPARE is made, possible existing parameters are bound and a subsequent EXECUTE does the job. SELECT isn't supported since $dbh->do doesn't give back a statement handler hence no way to retrieve data.

Binary Data

Fetching binary data from char and varchar fields is not guaranteed to work, but probably will most of the time. Use 'BYTE' or 'BYTE VARYING' data types in your database for full binary data support.

Long Data Types

DBD::Ingres supports the LONG VARCHAR and LONG BYTE data types as detailed in "Handling BLOB / LONG / Memo Fields" in DBI.

The default value for LongReadLen in DBD::Ingres is 2GB, the maximum size of a long data type field. DBD::Ingres dynamically allocates memory for long data types as required, so setting LongReadLen to a large value does not waste memory.

In summary:

Due to their size (and hence the impracticality of copying them inside the DBD driver), variables bound as blob types are always evaluated at execute time rather than bind time. (Similar to bind_param_inout, except you don't pass them as references.)

ing_readonly

Normally cursors are declared READONLY to increase speed. READONLY cursors don't create exclusive locks for all the rows selected; this is the default.

If you need to update a row then you will need to ensure that either

E.g.,

  $sth = $dbh->prepare("select ....", {ing_readonly => 0});

will be opened for update, as will

  $sth = $dbh->prepare("select .... for direct update of ..")

while

  $sth = $dbh->prepare("select .... for direct update of ..",
                       { ing_readonly => 1} );

will be opened FOR READONLY.

When you wish to actually do the update, where you would normally put the cursor name, you put:

  $sth->{CursorName}

instead, for example:

  $sth = $dbh->prepare("select a,b,c from t for update of b");
  $sth->execute;
  $row = $sth->fetchrow_arrayref;
  $dbh->do("update t set b='1' where current of $sth->{CursorName}");

Later you can reexecute the statement without the update-possibility by doing:

  $sth->{ing_readonly} = 1;
  $sth->execute;

and so on. Note that an update will now cause an SQL error.

In fact the "FOR UPDATE" seems to be optional, i.e., you can update cursors even if their SELECT statements do not contain a for update part.

If you wish to update such a cursor you must include the ing_readonly attribute.

NOTE DBD::Ingres version later than 0.19_1 have opened all cursors for update. This change breaks that behaviour. Sorry if this breaks your code.

ing_rollback

The DBI docs state that 'Changing AutoCommit from off to on will trigger a commit'.

Setting ing_rollback to on will change that to 'Changing AutoCommit from off to on will trigger a rollback'.

Default value is off.

NOTE Since DBD::Ingres version 0.53 ing_rollback has also an impact on the behavior on disconnect . Earlier versions always did a rollback, when disconnecting while a transaction was active. Now despite the state of AutoCommit the action (rollback/commit) is determined on the state of ing_rollback. If it's on, a rollback is done, otherwise a commit takes place. So if AutoCommit is off, and you disconnect without commiting, all your work would be treated like one big transaction.

Please take that in mind: This is just due to compatibility to other databases. Correct would be a commit at the end of the transaction, before disconnecting...

ing_statement

This has long been deprecated in favor of $sth->{Statement}, which is a DBI standard.

$sth->{ing_statement} provides access to the SQL statement text.

ing_types

  $sth->{ing_types}              (\@)

Returns an array of the "perl"-type of the return fields of a select statement.

The types are represented as:

'i': integer

All integer types, i.e., int1, int2 and int4.

These values are returned as integers. This should not cause loss of precision as the internal Perl integer is at least 32 bit long.

'f': float

The types float, float8 and money.

These values are returned as floating-point numbers. This may cause loss of precision, but that would occur anyway whenever an application referred to the data (all Ingres tools fetch these values as floating-point numbers)

'l': long / blob

Either of the two long datatypes, long varchar or long byte.

's': string

All other supported types, i.e., char, varchar, text, date etc.

Ingres Types and their DBI Equivalents

  $sth->TYPE                       (\@)

See DBI for a description. The Ingres translations are:

Have I forgotten any?

ing_lengths

  $sth->{ing_lengths}              (\@)

Returns an array containing the lengths of the fields in Ingres, eg. an int2 will return 2, a varchar(7) 7 and so on.

Note that money and date fields will have length returned as 0.

$sth->{SqlLen} is the same as $sth->{ing_lengths}, but the use of it is deprecated.

See also the $sth->{PRECISION} field in the DBI docs. This returns a 'reasonable' value for all types including money and date-fields.

ing_sqltypes

    $sth->{ing_sqltypes}              (\@)

Returns an array containing the Ingres types of the fields. The types are given as documented in the Ingres SQL Reference Manual.

All values are positive as the nullability of the field is returned in $sth->{NULLABLE}.

See also the $sth->{TYPE} field in the DBI docs.

ing_ph_ingtypes

    $sth->{ing_ph_ingtypes}           (\@)

Returns an array containing the Ingres types of the columns the placeholders represent. This is a guess from the context of the placeholder in the prepared statement. Be aware, that the guess isn't always correct and sometypes a zero (illegal) type is returned. Plus negative values indicate nullability of the parameter. A $sth->{ing_ph_nullable} field is to be implemented yet.

ing_ph_inglengths

    $sth->{ing_ph_inglengths}         (\@)

Returns an array containing the lengths of the placeholders analog to the $sth->{ing_lengths} field.

FEATURES NOT IMPLEMENTED ^

state

  $h->state                (undef)

SQLSTATE is not implemented.

disconnect_all

Not implemented

commit and rollback invalidate open cursors

DBD::Ingres should warn when a commit or rollback is isssued on a $dbh with open cursors.

Possibly a commit/rollback should also undef the $sth's. (This should probably be done in the DBI-layer as other drivers will have the same problems).

After a commit or rollback the cursors are all ->finish'ed, i.e., they are closed and the DBI/DBD will warn if an attempt is made to fetch from them.

A future version of DBD::Ingres wil possibly re-prepare the statement.

This is needed for

Cached statements

A new feature in DBI that is not implemented in DBD::Ingres.

bind_param_inout (Procedure calls)

It is possible to call database procedures from DBD::Ingres. It is NOT possible to get return values from the procedure.

A solution is underway for support for procedure calls from the DBI. Until that is defined procedure calls can be implemented as a DB::Ingres-specific function (like get_event) if the need arises and someone is willing to do it.

NOTES ^

$dbh->table_info, $dbh->column_info, $dbh->get_info

The table_info and column_info functions are just working against tables. Views and synonyms still have to be implemented. The get_info function returns just the newer version strings correctly, since I'm still looking for documentation for the older ones.

I wonder if I have forgotten something?

SEE ALSO ^

The DBI documentation in DBI and DBI::DBD.

AUTHORS ^

DBI/DBD was developed by Tim Bunce, <Tim.Bunce@ig.co.uk>, who also developed the DBD::Oracle that is the closest we have to a generic DBD implementation.

Henrik Tougaard, <htoug@cpan.org> developed the DBD::Ingres extension.

Stefan Reddig, <sreagle@cpan.org> is currently (2008) adopting it to include some more features.

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