Package org.geotools.data.duckdb

Class DuckDBDialect

  • Direct Known Subclasses:
    GeoParquetDialect
    public class DuckDBDialect
extends BasicSQLDialect
    Base SQL Dialect for DuckDB-based datastores. Provides common DuckDB SQL functionality including spatial support.

    This dialect implements the core SQL operations for DuckDB, with a focus on spatial functionality. It provides implementations for:

    • Geometry handling (WKB encoding/decoding, spatial function mapping)
    • SQL type conversions for geometry classes
    • Filter and query translation
    • Extension management (spatial, etc.)
    • Optimized bounds calculations
    • Geometry simplification for rendering

    This base dialect is extended by format-specific dialects like GeoParquetDialect to provide specialized functionality for different data formats while sharing the common DuckDB handling code.

    DuckDB is particularly well-suited for analytical workloads and includes excellent built-in support for spatial operations and columnar file formats like Parquet.

    • Constructor Detail

      • DuckDBDialect

        protected DuckDBDialect​(JDBCDataStore dataStore)

    • Method Detail

      • setScreenMapEnabled

        public void setScreenMapEnabled​(boolean screenMapEnabled)

      • setSimplifyEnabled

        public void setSimplifyEnabled​(boolean simplifyEnabled)

      • getDatabaseInitSql

        public List<String> getDatabaseInitSql()

      • getNameEscape

        public String getNameEscape()
        Description copied from class: SQLDialect
        Returns the string used to escape names.

        This value is used to escape any name in a query. This includes columns, tables, schemas, indexes, etc... If no escape is necessary this method should return the empty string, and never return null.

        This default implementation returns a single double quote ("), subclasses must override to provide a different espcape.

        Overrides:
        getNameEscape in class SQLDialect

      • escapeName

        public String escapeName​(String name)
        Description copied from class: SQLDialect
        Surrounds a name with the SQL escape string.

        If the name contains the SQL escape string, the SQL escape string is duplicated.

        Overrides:
        escapeName in class SQLDialect

      • includeTable

        public boolean includeTable​(String schemaName,
                            String tableName,
                            Connection cx)
                     throws SQLException
        Description copied from class: SQLDialect
        Determines if the specified table should be included in those published by the datastore.

        This method returns true if the table should be published as a feature type, otherwise it returns false. Subclasses should override this method, this default implementation returns true.

        A database connection is provided to the dialect but it should not be closed. However any statements objects or result sets that are instantiated from it must be closed.

        Overrides:
        includeTable in class SQLDialect
        Parameters:
        schemaName - The schema of the table, might be null..
        tableName - The name of the table.
        cx - Database connection.
        Throws:
        SQLException

      • registerSqlTypeToClassMappings

        public void registerSqlTypeToClassMappings​(Map<Integer,​Class<?>> mappings)
        Appends a mapping of Types.STRUCT to java.sql.Struct.class

        Support for struct is limited and results in GeoServer WMS and WFS to interpret it as a String literal. For example, a "bbox" Struct attribute value with SQL type name as STRUCT(xmin FLOAT, xmax FLOAT, ymin FLOAT, ymax FLOAT) will be encoded as <bbox>{xmin=-63.005005, xmax=-63.004997, ymin=-40.81569, ymax=-40.81568}</bbox> by virtue of DuckDBStruct.toString()

        Overrides:
        registerSqlTypeToClassMappings in class SQLDialect

      • registerClassToSqlMappings

        public void registerClassToSqlMappings​(Map<Class<?>,​Integer> mappings)
        Maps Geometry types to Types.OTHER and Struct to Types.STRUCT

        Support for struct is limited and results in GeoServer WMS and WFS to interpret it as a String literal. For example, a "bbox" Struct attribute value with SQL type name as STRUCT(xmin FLOAT, xmax FLOAT, ymin FLOAT, ymax FLOAT) will be encoded as <bbox>{xmin=-63.005005, xmax=-63.004997, ymin=-40.81569, ymax=-40.81568}</bbox> by virtue of DuckDBStruct.toString()

        Overrides:
        registerClassToSqlMappings in class SQLDialect

      • encodePostColumnCreateTable

        public void encodePostColumnCreateTable​(AttributeDescriptor att,
                                        StringBuffer sql)
        Description copied from class: SQLDialect
        Encodes anything post a column in a CREATE TABLE statement.

        This is appended after the column name and type. Subclasses may choose to override this method, the default implementation does nothing.

        Overrides:
        encodePostColumnCreateTable in class SQLDialect
        Parameters:
        att - The attribute corresponding to the column.

      • getGeometrySRID

        public Integer getGeometrySRID​(String schemaName,
                               String tableName,
                               String columnName,
                               Connection cx)
                        throws SQLException
        Description copied from class: SQLDialect
        Returns the spatial reference system identifier (srid) for a particular geometry column.

        This method is given a direct connection to the database. The connection must not be closed. However any statements or result sets instantiated from the connection must be closed.

        In the event that the srid cannot be determined, this method should return null .

        Overrides:
        getGeometrySRID in class SQLDialect
        Parameters:
        schemaName - The database schema, could be null.
        tableName - The table, never null.
        columnName - The column name, never null
        cx - The database connection.
        Throws:
        SQLException

      • getOptimizedBounds

        public List<ReferencedEnvelope> getOptimizedBounds​(String schema,
                                                   SimpleFeatureType featureType,
                                                   Connection cx)
                                            throws SQLException,
                                                   IOException
        Description copied from class: SQLDialect
        Returns the bounds of all geometry columns in the layer using any approach that proves to be faster than the plain bounds aggregation (e.g., better than the "plain select extent(geom) from table" on PostGIS), or null if none exists or the fast method has not been enabled (e.g., if the fast method is just an estimate of the bounds you probably want the user to enable it manually)
        Overrides:
        getOptimizedBounds in class SQLDialect
        Parameters:
        schema - The database schema, if any, or null
        featureType - The feature type containing the geometry columns whose bounds need to computed. Mind, it may be retyped and thus contain less geometry columns than the table
        Returns:
        a list of referenced envelopes (some of which may be null or empty)
        Throws:
        SQLException
        IOException

      • encodeGeometryColumn

        public void encodeGeometryColumn​(GeometryDescriptor gatt,
                                 String prefix,
                                 int srid,
                                 Hints hints,
                                 StringBuffer sql)
        Description copied from class: SQLDialect
        Encodes the name of a geometry column in a SELECT statement.

        This method should wrap the column name in any functions that are used to retrieve its value. For instance, often it is necessary to use the function asText, or asWKB when fetching a geometry.

        This method must also be sure to properly encode the name of the column with the SQLDialect.encodeColumnName(String, String, StringBuffer) function.

        Example: 

           
   sql.append( "asText(" );
   column( gatt.getLocalName(), sql );
   sql.append( ")" );
        Overrides:
        encodeGeometryColumn in class SQLDialect

      • decodeGeometryValue

        public Geometry decodeGeometryValue​(GeometryDescriptor descriptor,
                                    ResultSet rs,
                                    String column,
                                    GeometryFactory factory,
                                    Connection cx,
                                    Hints hints)
                             throws IOException,
                                    SQLException
        Description copied from class: SQLDialect
        Decodes a geometry value from the result of a query.

        This method is given direct access to a result set. The column parameter is the index into the result set which contains the geometric value.

        An implementation should deserialize the value provided by the result set into Geometry object. For example, consider an implementation which deserializes from well known text: 

           String wkt = rs.getString( column );
   if ( wkt == null ) {
     return null;
   }
   return new WKTReader(factory).read( wkt );
        Note that implementations must handle null values.

        The factory parameter should be used to instantiate any geometry objects.

        Specified by:
        decodeGeometryValue in class SQLDialect
        Throws:
        IOException
        SQLException

      • encodeGeometryValue

        public void encodeGeometryValue​(Geometry value,
                                int dimension,
                                int srid,
                                StringBuffer sql)
                         throws IOException
        Description copied from class: BasicSQLDialect
        Encodes a geometry value in an sql statement.

        An implementations should serialize value into some exchange format which will then be transported to the underlying database. For example, consider an implementation which converts a geometry into its well known text representation: 

           
   sql.append( "GeomFromText('" );
   sql.append( new WKTWriter().write( value ) );
   sql.append( ")" );

        The srid parameter is the spatial reference system identifier of the geometry, or 0 if not known.

        Attention should be paid to emtpy geometries (g.isEmtpy() == true) as they cannot be encoded in WKB and several databases fail to handle them property. Common treatment is to equate them to NULL

        Specified by:
        encodeGeometryValue in class BasicSQLDialect
        Throws:
        IOException

      • isConcreteGeometry

        protected boolean isConcreteGeometry​(Class<?> binding)

      • encodePrimaryKey

        public void encodePrimaryKey​(String column,
                             StringBuffer sql)
        Description copied from class: SQLDialect
        Encodes the primary key definition in a CREATE TABLE statement.

        Subclasses should override this method if need be, the default implementation does the following: 

           
   encodeColumnName( column, sql );
   sql.append( " int PRIMARY KEY" );
        Overrides:
        encodePrimaryKey in class SQLDialect

      • applyLimitOffset

        public void applyLimitOffset​(StringBuffer sql,
                             int limit,
                             int offset)
        Description copied from class: SQLDialect
        Alters the query provided so that limit and offset are natively dealt with. This might mean simply appending some extra directive to the query, or wrapping it into a bigger one.
        Overrides:
        applyLimitOffset in class SQLDialect