Categories:: Geospatial functions, Conversion functions

TRY_TO_GEOMETRY¶

Parses an input and returns a value of type GEOMETRY.

This function is identical to TO_GEOMETRY except that it returns NULL when TO_GEOMETRY would return an error.

See also:: TO_GEOMETRY

Syntax¶

Use one of the following:

TRY_TO_GEOMETRY( <varchar_expression> [ , <srid> ] [ , <allow_invalid> ] )

TRY_TO_GEOMETRY( <binary_expression> [ , <srid> ] [ , <allow_invalid> ] )

TRY_TO_GEOMETRY( <variant_expression> [ , <srid> ] [ , <allow_invalid> ] )

Arguments¶

Required:

varchar_expression

The argument must be a string expression that represents a valid geometric object in one of the following formats:

WKT (well-known text).
WKB (well-known binary) in hexadecimal format (without a leading 0x).
EWKT (extended well-known text).
EWKB (extended well-known binary) in hexadecimal format (without a leading 0x).
GeoJSON.

binary_expression

The argument must be a binary expression in WKB or EWKB format.

variant_expression

The argument must be an OBJECT in GeoJSON format.

Optional:

srid: The integer value of the SRID to use.

allow_invalid: If TRUE, specifies that the function returns a GEOGRAPHY or GEOMETRY object, even when the input shape isn’t valid and can’t be repaired. For more information, see Specifying how invalid geospatial shapes are handled.

Returns¶

The function returns a value of type GEOMETRY or NULL when TO_GEOMETRY would return an error.

Usage notes¶

Returns NULL if the input can’t be parsed as the appropriate supported format (WKT, WKB, EWKT, EWKB, GeoJSON).
For GeoJSON, WKT, and WKB input, if the srid argument is not specified, the resulting GEOMETRY object has the SRID set to 0.

Examples¶

This shows a simple use of the TRY_TO_GEOMETRY function with VARCHAR data:

SELECT TRY_TO_GEOMETRY('INVALID INPUT');

+----------------------------------+
| TRY_TO_GEOMETRY('INVALID INPUT') |
%----------------------------------%
| NULL                             |
+----------------------------------+

Create a temporary table and insert rows with GEOMETRY values:

CREATE OR REPLACE TEMP TABLE demo_to_geometry AS
SELECT
  1                                                     AS id,
  'POINT(10 20)'                                        AS wkt_col,         -- VARCHAR (WKT)
  'SRID=32633;POINT(500000.0 4649776.22)'               AS ewkt_col,        -- VARCHAR (EWKT)
  ST_ASWKB(TO_GEOMETRY('LINESTRING(0 0, 1 1)'))         AS wkb_bin_col,     -- BINARY (WKB)
  PARSE_JSON('{"type":"Point","coordinates":[10,20]}')  AS geojson_col,     -- VARIANT (GeoJSON)
  TO_GEOGRAPHY('POINT(-122.35 37.55)')                  AS geog_col,        -- GEOGRAPHY
  'POLYGON((0 0,2 2,2 0,0 2,0 0))'                      AS invalid_wkt_col, -- invalid shape
  0                                                     AS srid0,           -- SRID columns to show positional args
  3857                                                  AS srid_col,
  TRUE                                                  AS allow_true,      -- allow_invalid flags from columns
  FALSE                                                 AS allow_false
UNION ALL
SELECT
  2,
  'LINESTRING(0 0, 10 10)',
  'SRID=32633;POINT(389866.35 5819003.03)',
  ST_ASWKB(TO_GEOMETRY('POINT(2 3)')),
  PARSE_JSON('{"type":"LineString","coordinates":[[0,0],[1,1]]}'),
  TO_GEOGRAPHY('LINESTRING(-124.2 42,-120.01 41.99)'),
  'POLYGON((0 0,1 1,1 0,0 1,0 0))',
  0,
  3857,
  TRUE,
  FALSE;

This table has columns with data types that the TO_GEOMETRY function accepts as inputs in the following formats:

VARCHAR (WKT/WKB and hex/EWKT/EWKB/GeoJSON)
BINARY (WKB/EWKB)
VARIANT (GeoJSON object)
GEOGRAPHY

Optional srid and allow_invalid values can follow any of these formats. The St_Aswkb function generates valid WKB BINARY values.

The following example tries to convert VARCHAR values in the invalid_wkt_col column to GEOMETRY values, but the shapes aren’t valid:

ALTER SESSION SET GEOMETRY_OUTPUT_FORMAT='EWKT';

SELECT id, TRY_TO_GEOMETRY(invalid_wkt_col) AS g_or_null
  FROM demo_to_geometry;

+----+-----------+
| ID | G_OR_NULL |
|----+-----------|
|  1 | NULL      |
|  2 | NULL      |
+----+-----------+