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"PostGIS" (Data Connection)

"PostGIS" (Data Connection)

Details

Properties

  • DataConnectionObject[assoc] creates a reference to a data source. The source does not need to exist yet.
  • General keys typically found in assoc are:
  • "ConnectionName""PostGIS"
    "Location"SQL query given as a string
    "Redownload"whether to rerun the query and overwrite cached results
  • Required keys in assoc are:
  • "DatabaseName"string giving the database to access
    "Host"the host servicing the database
  • Typical keys in assoc are:
  • "Port"the server port to access the database
  • Possible forms of "Location" when connecting to a PostGIS database include:
  • "query"SQL query given as a string

    • Account Setting & Authentication

  • Possible values for Authentication are:
  • Automaticattempt to use saved credentials or give a dialog
    "Dialog"give authentication parameters via a dialog
    SystemCredential["key"]retrieve authentication information from secure storage
    SystemCredentialData[…]stored authentication data
    assocprovide explicit credentials
  • Use the form Authentication:>SystemCredential["key"] to delay evaluating securely stored credentials.
  • The following keys are accepted by Authenticationassoc:
  • "Username"username
    "Password"password

    • Examples

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    Basic Examples  (2)

    Create a DataConnectionObject to data from a PostgreSQL query:

    Wolfram Language code: DataConnectionObject[<|"ConnectionName" -> "PostGIS", "Host" -> "geo.example.com", "Port" -> 5432, "DatabaseName" -> "postgistest", "Location" -> "SELECT * FROM cities WHERE NOT (geom_polygon IS NULL) LIMIT 3"|>, Authentication -> <|"Username" -> "user", "Password" -> "pass"|>]

    Retrieve the data using Import:

    Wolfram Language code: Import@DataConnectionObject[<|"ConnectionName" -> "PostGIS", "Host" -> "geo.example.com", "Port" -> 5432, "DatabaseName" -> "postgistest", "Location" -> "SELECT * FROM cities WHERE NOT (geom_polygon IS NULL) LIMIT 3"|>, Authentication -> <|"Username" -> "user", "Password" -> "pass"|>]

    Scope  (1)

    Retrieve data from a PostGIS database:

    Wolfram Language code: data = Import[DataConnectionObject[<|"ConnectionName" -> "PostGIS", "Host" -> "geo.example.com", "Port" -> 5432, "DatabaseName" -> "postgistest", "Location" -> "SELECT entity, geog_polygon, st_buffer(geog_polygon, 1000) FROM cities WHERE NOT (geom_polygon IS NULL) limit 10"|>, Authentication -> <|"Username" -> "user", "Password" -> "pass"|>]]

    Use the polygon data to draw a map of regions around Dresden:

    Wolfram Language code: GeoGraphics[{Green, data[[1, 3]], Red, data[[1, 2]]}]