TRY_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 , ST_ASBINARY 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      |
+----+-----------+