abstract class %SQL.FDW.Abstract
extends %RegisteredObject, %SQL.StatementResult
Abstract class providing interface for Foreign Data Wrappers.
Foreign Data Wrappers provide the API for interacting with data stored in foreign sources
such as CSV files, external databases, distributed file servers etc.
• parameter PREDICATEPUSHDOWN = 0;
Specifies whether this foreign data wrapper supports pushing logical predicates to its source.
0 by default, overridden to be 1 by the XDBC FDW
• property %AtEnd
as %Boolean;
Whether we are at the end of the entire result set
• property %GetData
as %String [ MultiDimensional ];
Multidimensional property that stores the current row being fetched, where each
node of the property is indexed by column number and the node data is the field value.
This is where the field data is accessed by cached queries and "overrides" the %GetData() method
of the %SQL.StatementResult parent class
• property %ResultSetColumnCount
as %Integer;
• property Buffer
as %List;
The current buffer (batch of rows - a $lb of $lb's)
• property BufferLength
as %Integer;
The size of the buffer (number of characters)
• property BufferPointer
as %Integer;
Maintains the pointer output by $listnext
• property RemainingBuffers
as %Boolean;
Whether there are more buffers (batches of rows) that the source can return
• method %Next(ByRef sc As %Library.Status = $$$OK)
as %Library.Integer
Advance the result set cursor to the next row. Returns 0 if the cursor is at the end of the
result set.. An optional argument contains a %Library.Status value on return. This %Status value
indicates success or failure of the %Next call. %SQLCODE is also set by %Next.
• method CleanUp(StopLanguageServer As %Boolean)
as %Status
Disconnect Gateway, optionally stop External Language Server (costly to start it again).
• method Close()
as %Status
Corresponds to *Close of TVF
• method Execute(Server As %String, FTClassName As %String, Query As %String, Parameters As %List)
as %Status
Corresponds to *Execute of a TVF
• method Fetch(ByRef Row As %List, ByRef AtEnd As %Integer)
as %Status
Corresponds to *Fetch of a TVF
• method GetRequestObject(Server As %String, FTClassName As %String)
as %Library.DynamicObject
Create the request string sent to Java
• classmethod QuoteIdentifier(identifier As %String, supportsDelimitedIdentifiers As %Boolean)
as %String
Quote identifiers appropriately for the data source type that this foreign data wrapper wraps based
on whether delimited identifiers should be supported.
Default implementation returns the identifier as is. It is up to the subclass to implement the behavior
appropriate for the data source type.
• method Reset()
as %Status
Reset the result set back to the first row. Note this may entail a full re-execution depending on the specific
implmentation of the foreign data wrapper.
