Cadcorp View Geometry

A read-only view of a database table that has a column of item geometry, stored as Binary Large Objects (BLOBs). 

Feature table and feature code can be assigned during import by aliasing data columns.

Compatibility:

• Cadcorp SIS Desktop
• Cadcorp SIS Desktop Express
• Cadcorp SIS ActiveX Modeller
• Cadcorp SIS ActiveX Manager
• Cadcorp SIS ActiveX Viewer
• Cadcorp GeognoSIS

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Dataset Properties

• Attributes: _attributes$
  A list of attributes held by the dataset.
  
  
• Blob format: _blobFormat$
  A description of the format of blobs used to represent items,
  
  
• Class name: _class$
  The class name of the dataset.
  
  
• Column aliases: _aliases$
  A comma-separated list of column aliases in the dataset's recordset.
  
  
• Column names: _columns$
  A comma-separated list of column names in the dataset's recordset.
  
  
• Coordinate Reference System: _projection$
  The dataset Coordinate Reference System in Open Geospatial Consortium (OGC) Well-Known-Text format. (Notice that some SIS Coordinate Reference System objects are not supported in OGC.)
  
  
• Description: _DESC$
  A textual description of the object.
  
  
• EPSG Code: _epsg&
  The matching EPSG code, if any.
  
  
• Editable: _bEditable&
  Is the dataset editable?
  
  
• Feature table: _featureTable$
  The Feature Table which dataset items with no Feature Table of their own use when their Feature code is set. This Feature Table is also used to get information about available feature codes, and to create a default Feature Filter.
  
  Note: This does not override the Feature Table on an item.
  
  
• Fetch size: _fetchSize&
  The size of a SQL fetch used when retrieving a Blob string from the database table, in the range 1KB (1024) to 1MB (1024*1024).
  
  This value is only used when the _MaxBlobSize& property is set to 0, and the database cannot tell Cadcorp SIS Desktop how long the Blob string is. In this case, Cadcorp SIS Desktop will get chunks of bytes, where the starting chunk size is this value, until the whole Blob string has been read. Each subsequent chunk size is twice the previous chunk size. For example, if this value is set to 4KB (4096), then the chunk sizes will be 4KB, 8KB, 16KB, 32KB, etc., until the whole Blob string has been read.
  
  Care should be taken when setting this value, because the wrong value, either too large or too small, could have a significant effect on Blob loading times.
  
  Note: If this value is 0 then the default fetch size will be used (currently 64KB).
  
  
• Layers: _layers$
  The set of all values the Layer property for all items in the dataset.
  
  
• Maximum Blob size: _MaxBlobSize&
  The maximum length of a Blob string in the database table, in the range 1KB (1024) to 4MB (4*1024*1024).
  
  If this value is set to 0 then Blob strings of any size can be read and written, with no limit other than available memory.
  
  
• Maximum number of open Gateways: _nMaxGatewayOpen&
  The maximum number of Gateway sub-datasets a dataset should attempt to open simultaneously.
  
  
• Maximum range per SQL SELECT: _MaxRangePerSql&
  Controls the number of SQL SELECT-s used when a database-based dataset which uses a Spatial Reference asks the dataset for items within a view.
  
  
• Modified: _bModified&
  Has the dataset been modified?
  
  
• Name: _name$
  The dataset name. For a file-based dataset this will be the filename.
  
  
• Next item id: _idNextItem&
  The Item ID which will be used for the next Item created in this dataset.
  
  
• Notes: _notes$
  User notes on dataset.
  
  
• Number of Items: _nItems&
  The number of items in the dataset.
  
  
• Scale: _scale#
  The dataset scale.
  
  
• Service name: _service$
  The name of the service.
  
  
• Size: _size&
  The amount of memory, in bytes, that the dataset uses.
  
  
• SQL WHERE expression: _where$
  The SQL WHERE expression in a dataset's recordset.
  
  
• Table names: _tables$
  A comma-separated list of table names in a database dataset's recordset.
  
  
• Textual Blobs: _bTextBlob&
  Are item blobs in ASCII text format, or binary? This affects how Cadcorp SIS Desktop communicates with the dataset's database.
  
  
• User name: _user$
  This reports: _name$, _DESC$, _crs$, _epsg&, _loadTime#.
  
  
• report: _report$
  This reports: _name$, _DESC$, _crs$, _epsg&, _loadTime#.
  

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