Name
DIO — Database Interface Objects
Synopsis
::DIO::handle interface ?objectName? (-option | option | -option | option | ...)
Description
DIO is designed to be a generic,
object-oriented interface to SQL databases. Its main goal
is to be as generic as possible, but since not all SQL
databases support the exact same syntaxes, keeping code
generic between databases is left to the abilities of the
programmer. DIO simply provides a way to keep the Tcl
interface generic.
interface - The name of the database
interface. Currently supported interfaces are
Postgresql and Mysql.
If objectName is
specified, DIO creates an object of that name. If there is
no objectName
given, DIO will automatically generate a unique object ID
Options
The hostname of the computer to connect to. If none
is given, DIO assumes the local host.
The port number to connect to on hostname.
The username you wish to login to the server as.
The password to login to the server with.
The name of the database to connect to.
The default table to use when using built-in commands
for storing and fetching.
The default field to use as the primary key when using
built-in commands for storing and fetching.
If this option is set to 1, DIO will attempt to
determine an automatic key for
keyField when storing and fetching.
In most databases, this requires that the
sequence also be specified. In the
case of MySQL, where sequences do not exist, autokey
must be used in conjunction with a table which has a
field specified as AUTO.
If DIO is automatically generating keys, it will use
this sequence as a means to gain a unique number for
the stored key.
DIO Object Commands
objectName ?array? ?request?
Execute request as a SQL query and
create an array from the first record found. The
array is set with the fields of the table and the
values of the record found.
objectName ?autokey? (value | boolean)
Return the current autokey value. If
value is specified, it sets a new
value for the autokey option.
Close the current database connection. This command is
automatically called when the DIO object is destroyed.
Return a count of the number of rows in the
specified (or current) table.
Return the current database. If
value is specified, it sets a new
value for the database. In most cases, the DIO object
will automatically connect to the new database when
this option is changed.
objectName ?delete? ?key? (-option | option | ...)
Delete a record from the database where the primary
key matches key.
objectName ?errorinfo? ?value?
errorinfo contains the value of
the last error, if any, to occur while executing a
request. When a request fails for any reason, this
variable is filled with the error message from the SQL
interface package.
objectName ?exec? ?request?
Execute request as an SQL query.
When the exec command is called, the query is
executed, and a DIO result object is returned. From
there, the result object can be used to obtain
information about the query status and records in a
generic way. See
Result
Object Commands
objectName ?fetch? ?key? ?arrayName? (-option | option | ...)
Fetch a record from the database where the primary key
matches key and store the result in
an array called arrayName.
objectName ?forall? ?request? ?arrayName? ?body?
Execute an SQL select request and iteratively
fill the array named arrayName
with elements named with the matching field names, and
values containing the matching values, repeatedly executing
the specified code body
for each row returned.
objectName ?host? ?value?
Return the current host value. If
value is specified, it sets a new
value for the host.
objectName ?insert? ?table? ?arrayName? (-option | option | ...)
Insert fields from arrayName into the specified table in the database.
Return the database interface type, such as
Postgresql or Mysql.
objectName ?keyfield? ?value?
Return the current keyfield. If
value is specified, it sets a new
value for the keyfield. Value can contain
multiple key fields as a Tcl list, if the table has multiple
key fields.
objectName ?keys? ?pattern? (-option | option | ...)
Return a list of keys in the database. If
pattern is specified, only the keys
matching will be returned.
Return the last key that was used from
sequence. If sequence has not been
specified, this command returns an empty string.
objectName ?list? ?request?
Execute request as a SQL query and
return a list of the first column of each record
found.
objectName ?makekey? ?arrayName? ?keyfield?
Given an array containing key-value pairs and an optional
list of key fields (we use the object's keyfield if
none is specified), if we're doing auto keys, create
and return a new key, otherwise if it's a single key,
just return its value from the array, else if there are
multiple keys, return all the keys' values from the
array as a list.
Increment sequence and return the
next key to be used. If sequence has not been
specified, this command returns an empty
string.
Open the connection to the current database. This
command is automatically called from any command which
accesses the database.
objectName ?pass? ?value?
Return the current pass value. If
value is specified, it sets a new
value for the password.
objectName ?port? ?value?
Return the current port value. If value is
specified, it sets a new value for the port.
objectName ?quote? ?string?
Return the specified string quoted in
a way that makes it acceptable as a value in a SQL statement.
objectName ?search? (-option | option | ...)
Search the current table, or the specified table if
-table tableName is specified, for rows matching
one or more fields as key-value pairs, and return
a query result handle.
See
Result Object Commands
For example,
set res [DIO search -table people -firstname Bob]
objectName ?sequence? ?value?
Return the current sequence value. If value is
specified, it sets a new value for the sequence.
objectName ?store? ?arrayName? (-option | option | ...)
Store the contents of arrayName in the
database, where the keys are the field names and the
array's values are the corresponding values. Do an SQL insert
if the corresponding row doesn't exist, or an update
if it does.
The table name must have been previously set
or specified with ?-table?, and the key field(s) must
have been previously set or specified with
?-keyfield?.
Please note that the store method has significantly higher
overhead than
the update or insert methods, so if you know you are
inserting a row rather than updating one, it is advisable
to use the insert method and, likewise, if you know you
are updating rather than inserting, to use the
update method.
objectName ?string? ?request?
Execute request as a SQL query and
return a string containing the first record
found.
objectName ?table? ?value?
Return the current table. If
value is specified, it sets a new
value for the table.
objectName ?update? ?arrayName? (-option | option | ...)
Updates the row matching the contents of
arrayName in the database. The matching
row must already exist. The table can have already been
set or can be specified with ?-table?, and
the key field(s) must either have been set or
specified with ?-keyfield?.
objectName ?user? ?value?
Return the current user value. If
value is specified, it sets a new
value for the user.
Result Object Commands
resultObj ?autocache? ?value?
Return the current autocache value. If
value is specified, it sets a new
value for autocache.
If autocache is true, the result object will
automatically cache rows as you use them. This means
that the first time you execute a forall command, each
row is being cached in the result object itself and
will no longer need to access the SQL result.
Default is true.
Cache the results of the current SQL result in the
result object itself. This means that even if the
database connection is closed and all the results of
the DIO object are lost, this result object will still
maintain a cached copy of its records.
resultObj ?errorcode? ?value?
Return the current errorcode value. If value
is specified, it sets a new value for errorcode.
errorcode contains the current code from the
SQL database which specifies the result of the query
statement which created this object. This variable
can be used to determine the success or failure of a
query.
resultObj ?errorinfo? ?value?
Return the current errorinfo value. If value
is specified, it sets a new value for errorinfo.
If an error occurred during the SQL query, DIO
attempts to set the value of errorinfo to the
resulting error message.
resultObj ?fields? ?value?
Return the current fields value. If
value is specified, it sets a new
value for fields.
fields contains the list of fields
used in this query. The fields are in order of the
fields retrieved for each row.
resultObj ?forall? ?-type? ?varName? ?body?
Execute body over each record in the
result object.
Types:
Create
varName
as an array where the indexes are the names of
the fields in the table and the values are the
values of the current row.
Set
varName
to a list containing key-value pairs of fields
and values from the current row. (-field value
-field value)
Set
varName
to a list that contains the values of the
current row.
resultObj ?next? ?-type? ?varName?
Retrieve the next record in the result object.
Types:
Create
varName
as an array where the indexes are the names of
the fields in the table and the values are the
values of the current row.
Set
varName
to a list containing key-value pairs of fields
and values from the current row. (-field value
-field value)
Set
varName
to a list that contains the values of the
current row.
resultObj ?numrows? ?value?
Return the current numrows value. If value is
specified, it sets a new value for numrows.
numrows is the number of rows in this result.
resultObj ?resultid? ?value?
Return the current resultid value. If value is
specified, it sets a new value for resultid.
resultid in most databases is the result
pointer which was given us by the database. This
variable is not generic and should not really be used,
but it's there if you want it.
resultObj ?rowid? ?value?
Return the current rowid value. If value is
specified, it sets a new value for rowid.
rowid contains the number of the
current result record in the result object. This
variable should not really be accessed outside of the
result object, but it's there if you want it.
