FNC_GeomSetWKTClob Function | C Library Functions | Teradata Vantage - 17.10 - FNC_GeomSetWKTClob - Advanced SQL Engine - Teradata Database

Teradata Vantageā„¢ - SQL External Routine Programming

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1147-171K
Language
English (United States)

Set the value of a Geometry type using a Well-Known Text (WKT) CLOB represented by a LOB_RESULT_LOCATOR.

Syntax

void
FNC_GeomGetWKTClob(GEO_HANDLE          geoHandle,
                   LOB_RESULT_LOCATOR  geoClob,
                   int                 srid)

Syntax Elements

geoHandle
A handle to a Geometry type that is defined to be a return value for a UDF/UDM or an INOUT/OUT parameter to an external stored procedure.
geoClob
LOB locator for the WKT CLOB containing the return value for the ST_Geometry type in the Latin character set.
srid
Spatial Reference System Identifier of the Geometry to be set.

Usage Notes

The FNC_GeomSetWKTClob function sets the ST_Geometry return/OUT/INOUT parameter value using a LOB result locator. The ST_Geometry Handle geoHandle is passed as input along with a LOB result locator geoClob.. The geoClob locator value is obtained by calling FNC_GeomGetResultWKTClob, and LOB FNC routines are used to append the WKT value to the CLOB. It is then passed to the FNC_GeomSetWKTClob routine. The CLOB should be in the Latin character set.

The CLOB returned by this routine must contain well-formed WKT data else the FNC routine will return an error ERRAMPFNCUDTBADARG.

FNC_GeomSetWKTClob should be used only with a LOB-based ST_Geometry value. Otherwise a 7579 error is generated: FNC_GeomSetWKTClob is only valid for LOB-based ST_Geometry values. Use FNC_GeomSetWKT() instead.

Example: Using FNC_GeomGetResultWKTClob and FNC_GeomSetWKTClob to retrieve and set the value of a return ST_Geometry

The following function takes an ST_Geometry parameter and returns an ST_Geometry that has the same value. It first retrieves the Well-Known Text format from the input geometry. It then retrieves the LOB result locator from the return ST_Geometry, appends the WKT to the CLOB, and then sets the CLOB into the return ST_Geometry.

REPLACE FUNCTION geo_wkt(p1 ST_Geometry)
RETURNS ST_Geometry
SPECIFIC geo_wkt
NO SQL
PARAMETER STYLE SQL
DETERMINISTIC
LANGUAGE C
EXTERNAL NAME 'CS!geo_wkt!geo_wkt.c!F!geo_wkt';

#define SQL_TEXT Latin_Text
#include <sqltypes_td.h>
#include <string.h>

void geo_wkt( GEO_HANDLE  *geo_in,
              GEO_HANDLE  *geo_out,
              int         *indicator_geo_in,
              int         *indicator_geo_out,
              char        sqlstate[6],
              SQL_TEXT    extname[129],
              SQL_TEXT    specific_name[129],
              SQL_TEXT    error_message[257])
{
    LOB_RESULT_LOCATOR geoClob_out;
    LOB_LOCATOR geoClob_in;
    BYTE buffer[64000];
    LOB_CONTEXT_ID id;
    FNC_LobLength_t actlen;
    int trunc_err = 0;
    FNC_LobLength_t clob_length;
    int srid = -1;
    int max_length, max_length2, numLobs, numLobs2;

    /* If input is null set return value to null. */
    if (*indicator_geo_in == -1 )
    {
        *indicator_geo_out = -1;
        return;
    }
    /* Get the Input Geometry Info */
     FNC_GetGeometryInfo(*geo_in,&max_length, &numLobs);

    /* Get the Output Geometry Info */
     FNC_GetGeometryInfo(*geo_out,&max_length2, &numLobs2);

    /* 
     * Copy geo_in ST_Geometry value to geo_out ST_Geometry value.
     *
     */
 
    if(numLobs ==1 && numLobs2==1)
    {
     /* Get the LOB_RESULT_LOCATOR of geo_out. */
      FNC_GeomGetResultWKTClob(*geo_out, &geoClob_out); 

     /* Get the LOB_LOCATOR and srid of the input ST_Geometry value. */
      FNC_GeomGetWKTClob(*geo_in, &geoClob_in, &srid); 

     FNC_LobOpen(geoClob_in, &id, 0, 0);

     clob_length = FNC_GetLobLength(geoClob_in);

     while (FNC_LobRead(id, buffer, clob_length, &actlen) == 0 && !trunc_err)
         trunc_err = FNC_LobAppend(geoClob_out, buffer, actlen, &actlen);

     FNC_LobClose(id);

     /* Set the return ST_Geometry value */
      FNC_GeomSetWKTClob(*geo_out, geoClob_out, srid);  
    }
}