This is a list of the standard Driver Parameters supported by the pgExpress Driver (please check your Delphi help on Driver Parameters for more information on each of them).
Table 2.2. Driver Parameters
Parameter | Obs. |
---|---|
DriverName | |
Database |
Used also to provide Special Params to the pgExpress Driver. This parameter can also be used as
an URL for providing extra host and port info:
host:port/databasePlease check the Installation section for more details. |
User_Name | |
Password | See also the Authentication section. |
BlobSize | This parameter is actually ignored, since PostgreSQL can report the exact Blob field size. |
LocaleCode | See also the Multibyte, UNICODE and Locales section. |
RowsetSize | Only works if the BlockRead param is True. |
HostName |
Name can instead be specified as a member of the Database paramater.
|
RoleName |
Will set a PostgreSQL7.3+ schema (namespace) to log in.
Please check here
for more details. Multiple Schemas can be specified (just as in PostgreSQL) if separated by
collons, such as:
RoleName = public,schema1,schema2 |
ServerCharset | See also Multibyte, UNICODE and Locales. |
Custom String |
This param allows to supply Special Params through
a way other then the traditional, i.e. after the
Database .
D7+ only.
|
ServerPort |
Allows setting the port to connect to. D7+ only.
Can instead be specified as a member of the
|
ConnectionTimeout |
The ConnectionTimeout Special Param
can be used on Delphi 6/7 too, or Kylix.
D7+ only.
|
BlockingMode | If False, asynchronous connections will be used to connect to the server. |
Decimal Separator | Same as ServerDecimalSeparator, but since BDS 2006, it is also supported as a regular dbExpress parameter. It will not work with applications built with older IDEs. |
ConnectionString |
dbExpress applications (BDS 2006+), support a custom connection string, that will be passed directly to
the PQconnectdb() function, and thus supporting anything that function supports.
You can use that parameter instead of Database parameter, User_Name parameter,
etc. Syntax will be the same as of the conninfo parameter of the
PQconnectdb()
function.
|
ErrorResourceFile |
Allows to set the language resource file for the driver. Please refer to
Multilanguage Driver section for more details.
Notes:The behavior for this parameter has changed on pgExpress v3.0. To get the same behavior as the v2.X series, check the Language. |
Trim Char | When True, trailing space chars CHAR fields will be trimmed. VCL/CLX default is False. |
The pgExpress Driver has a few special parameters that can be used to customize its behaviors; we refer to them as "Special Params". Default values are formatted like this.
To set a special param, add it in your dbxconnections(.ini)
file after the database parameter, such as:
[PGEConnection] Database=localhost/template1,TextAsMemo=False,ByteaMode=asVarBytes ...
Table 2.3. Special Params
Key | Values | Meaning | |||||
---|---|---|---|---|---|---|---|
TextAsMemo |
|
If True, the PostgreSQL TEXT fields will be mapped as Blob
(Memo); if False (default), it will be mapped as String. A
VARCHAR field with no length specifier behaves exactly like a TEXT field.
Obs:If mapped as string, a TEXT field will be padded at the maximum string length imposed by dbExpress (~32Kb). | |||||
NumericAsBcd |
| This special param has been deprecated and will be ignored as of pgExpress 4.0. Please refer to BorlandCompatible for a better solution. | |||||
MapUnknownAsString |
| If True, unknown/unsupported field types such as point will be mapped as strings. | |||||
ArrayAsString |
| If True, arrays will be mapped as strings. If False, they will be ignored (hidden). | |||||
ByteaMode |
|
This parameter controls to which type the bytea fields get mapped.
Check Bytea fields as BLOBs for more details. For compatibility with
pre-v3.50 behavior(TVarBytesField , set this to
asVarBytes .
New in version v3.50.
| |||||
Int8Mode |
|
Notes:
| |||||
QuoteObjects |
|
If True, quote objects names. To this setting to take effect, the connection must be reopened
(if already opened of course). An example of unquoted and quoted query:
Example 2.1. Quoted and unquoted queries select typname from pg_type; -- unquoted version select "typname" from "pg_type"; -- quoted version Please note that quoted objects names are case sensitive for PostgreSQL. The query above written like this would fail:
| |||||
TypesCachingMode |
|
This setting will control how often the types from PostgreSQL will be loaded and mapped into
VCL/CLX types. Of course the less times they are loaded, the faster the application
will be. The default setting should be OK for most applications (unless you do types
manipulation).
Obs:The PostgreSQL database has a flexible types support; that means we must retrieve the types information before we know what each type name means. This information is retrieved from the pg_type catalog and then mapped into actual dbExpress/VCL types by the pgExpress driver. Please refer to your PostgreSQL documentation for more details. | |||||
GetExtendedFieldsInformation |
|
If True, will retrieve extra information about the fields in a table (for single
table queries). That will allow the pgExpress Driver to determine if a field can be null
(ISQLCursor. ) or
are automatically generated by a sequence the server
(ISQLCursor. ).
Few applications should need this setting and they can be manually added to the
TFields list representing each physical field. Since this will
add a new query overhead for each cursor (TDataset ) retrieved, slowing
down the operation, it's adviced not to use it unless you need the information (for instance,
on situations where you don't know the structure of the table that is going to be open).
| |||||
ServerDecimalSeparator | (char) |
The pgExpress Driver should automatically detect your locale settings and use the appropriate decimal separator. However, if you want to force some specific value, this options is available. Set it to the char you want to be the decimal separator (usually either "." or ",").
However, since the ServerDecimalSeparator = \,
Another exemple:
ServerDecimalSeparator = .
See also ServerDecimalSeparator. | |||||
BlockRead |
|
If True, the pgExpress Driver will use Fetch Cursors to
retrieve the records from the server.
The standard It is required to use this parameter to read the records in blocks since the pgExpress Driver will have to use a totally different method to retrieve the records from the server. Please refer to the section for more details. | |||||
UseQualifiedNames |
|
If True, the pgExpress Driver will return qualified names on metadata retrieving, such as public.MyTable, pg_catalog.abstime, etc. This option will only work PostgreSQL 7.3 which supports schemas. | |||||
RestrictedNameSpace |
| Controls which metadata is retrieved. If True, only objects in the current namespace search path will be retrieved. If False, all objects will be retrieved, regardless of which namespace they are in. | |||||
RequireSSL |
|
If True, will only make a connection to the server in SSL mode. This option
will only work with a SSL enabled libpq (currently only under Linux ).
| |||||
ShowOID |
|
If True, the pgExpress Driver will return the OID
field in the list of fields for a table
(ISQLConnection. See also this FAQ entry on OIDs usage with pgExpress. | |||||
ConnectionTimeout | X |
Allows to specify connection timeouts (X in seconds).
It needs libpq v7.3 or above (included with pgExpress Driver). This
parameter is an integer value.
| |||||
AutoRecover |
|
If True, the pgExpress Driver will automatically try to detect if the connection has been broken
and recover it automatically and continue processing. If it is sucessful, the whole operation
is fully transparent to the user. If not, an appropriate error message will be displayed.
NoteThis feature is avaiable only on the registered version of the driver. | |||||
RetainCursor |
|
Controls the Retaining Cursors behavior. If True, the pgExpress Driver will retain the cursor for the previous SELECT statement and return it if a previous dataset record is acessed again, instead of running the whole query again (dbExpress behavior). No matter how many times the same query is run again, always the same result set is returned (from the internal cache). NoteThis setting will be ignored if Fetch Cursors are being used. | |||||
BlobWriting |
| If True, the pgExpress Driver will allow Blob (Large Objects) writes. Blob writing is a delicate issue; just activate this setting if you read Section 6.7.1, “Large Objects (BLOBs)”. Registered users only. | |||||
LogDeclareFetch |
|
If True, the pgExpress Driver will log (into An example of unfiltered output (LogDeclareFetch=False): Starting transaction for DECLARE/FETCH Starting transaction >> BEGIN; >> DECLARE pgeCursor CURSOR for select * from pg_type; >> FETCH 50 FROM pgeCursor >> FETCH 50 FROM pgeCursor >> FETCH 50 FROM pgeCursor >> FETCH 50 FROM pgeCursor >> FETCH 50 FROM pgeCursor Closing cursor pgeCursor >> CLOSE pgeCursor Ending DECLARE/FETCH transaction Rolling back transaction >> ROLLBACK;
The same operation, but filtered (LogDeclareFetch=True): >> BEGIN; Rolling back transaction >> ROLLBACK;
For more info on DECLARE/FETCH cursors, check Section 6.2, “Fetch Cursors”. Registered users only since depends on Section 6.2, “Fetch Cursors” | |||||
Language | (none) | If empty, the pgExpress Driver will assume the language to be used is English. Otherwise, it is one of the entries of the Supported languages table table. | |||||
Borland Compatible | False | If True, the pgExpress Driver will try to be more compatible with the behavior of Codegear dbExpress drivers, mapping NUMERIC values like Codegear does. | |||||
UnicodeAsWideChar | False |
If True, the pgExpress Driver will map string (CHAR,
VARCHAR, TEXT) fields
as TWideString , when using UNICODE client charset.
Note
This parameter is only meaningful for dbExpress protocol 3.0 and later applications, whose can map to
| |||||
DBX4Compatible | (auto) |
If True, the pgExpress Driver will get into dbExpress 4 compatibility mode. Among other things,
NUMERIC/DECIMAL fields will be mapped as TBcdField instead of
TFMTBcdField. Please read ??? for further information.
NoteThis parameter is only meaningful for dbExpress protocol 3.0 and later applications, running under dbExpress 4. |
On older pgExpress Driver versions, these parameters used go into the dbxdrivers(.ini)
file. But since version 1.5, they go
after the Database
parameter in the dbxconnections(.ini)
parameter,
separated by commas. On Delphi 7 or later, they can also go on the
Custom String
parameter.
Example 2.2. Special Parameters usage
[OfficeServer] Database = sales,TextAsMemo = False, Int8Mode = AsString [PGEConnection] Database = sales, ArrayAsString = False, QuoteObjects = True, GetExtendedFieldsInformation = False
On Delphi 7, using the new Custom String
section (works the same way as above, but this section was made for using with special
params):
Example 2.3. Special parameters usage with the Custom String
param
[PGEConnection] Database = sales Custom String = ArrayAsString = False, QuoteObjects = True, GetExtendedFieldsInformation = False
If you don't want to use any special parameters (as most users will), specify the Database parameter alone, normally:
[OfficeServer] Database = sales
Of course these parameters could also go in the
property as any other TSQLConnections
.
Paramsdbxconnections(.ini)
parameter:
SQLConnection1.Params.Add('Database = sales,TextAsMemo = False,Int8Mode = AsString');
Or on Delphi 7, using the new Custom String
section:
SQLConnection1.Params.Add('Custom String = ArrayAsString = False, QuoteObjects = True, GetExtendedFieldsInformation = False ');
Unhappily, due to the way dbExpress was designed on Delphi 6 and
Kylix 1/2/3
, there can't be real custom parameters from VCL/CLX to the driver, so misusing
the Database
parameter was a “hack” that
we had to do to allow custom params. Even on Delphi 7 only a
single Custom parameter (“Custom String”) can be specified.
"Custom Info" are methods that can be used to retrieve information from the driver that otherwise
could not be retrieved. They will only work with Delphi 7 or newer which
implements the eConnCustomInfo
interface.
For easy implementation of these interfaces, please use the corresponding functions from the
pgeDriverUtils.pas
unit.
Table 2.4. Custom Info Interfaces
Information | Meaning | Function |
---|---|---|
GetPGVersion | Returns the PostgreSQL server version as a float. | GetPGVersion |
TTY | Allows setting or retrieving file or TTY for optional debug output from the backend server. Set before connecting. | GetTTY |
BackendPID | Will retrieve the PID of the process of the connection in the backend server. | GetBackendPID |
Online |
Will return True if a connection to the server
exists. This implements the eCommOnline
interface.
| GetOnline |