check which well known text can be transformed using geometry::STPolyFromText( - tsql

Question

I have some data which I bulk import into this table structure:
CREATE TABLE #Temp
(
WellKnownText NVARCHAR(MAX)
)
Some of the entries are not valid. So something like this:
SELECT geometry::STPolyFromText(WellKnownText,4326) FROM #Temp
does not work for all rows and thus falls over.
What is the best way to detect which WellKnownText are not valid? I have used MakeValid in the past - so ideally I would like to fix entries as much as possible.
PS:
This does not work:
SELECT * FROM #Temp
WHERE geometry::STPolyFromText(WellKnownText,4326).STIsValid() = 0
PPS:
I chose a loop based approach in the end along those lines:
IF OBJECT_ID('tempdb..#Temp') IS NOT NULL DROP TABLE #Temp;
IF OBJECT_ID('tempdb..#Temp1') IS NOT NULL DROP TABLE #Temp1;
DECLARE #LoopCounter INT = 1;
DECLARE #MaxCounter INT;
DECLARE #Valid BIT;
DECLARE #ValidCounter INT;
DECLARE #WellKnownText NVARCHAR(MAX);
CREATE TABLE #Temp
(
Guid UNIQUEIDENTIFIER,
PostcodeFraction NVARCHAR(50),
WellKnownText NVARCHAR(MAX),
GeoJson NVARCHAR(MAX)
);
CREATE TABLE #Temp1
(
Guid UNIQUEIDENTIFIER,
PostcodeFraction NVARCHAR(50),
WellKnownText NVARCHAR(MAX),
GeoJson NVARCHAR(MAX)
);
BULK INSERT #Temp FROM 'D:\PolygonData.txt' WITH (FIELDTERMINATOR = '\t', FIRSTROW = 2, ROWTERMINATOR = '\n');
ALTER TABLE #Temp ADD Id INT IDENTITY(1,1);
SELECT #MaxCounter = MAX(Id) FROM #Temp
SET #ValidCounter = 0;
WHILE(#LoopCounter <= #MaxCounter)
BEGIN
BEGIN TRY
SELECT #WellKnownText = WellKnownText FROM #Temp WHERE Id = #LoopCounter;
SET #Valid = GEOMETRY::STGeomFromText(#WellKnownText,4326).STIsValid();
SET #ValidCounter = #ValidCounter + 1;
END TRY
BEGIN CATCH
SET #Valid = 0;
END CATCH
IF(#Valid = 1)
BEGIN
INSERT INTO #TEMP1
SELECT Guid, PostcodeFraction, WellKnownText, GeoJson FROM #Temp WHERE Id = #LoopCounter;
END
SET #LoopCounter = #LoopCounter + 1;
END
PRINT #ValidCounter;
SELECT * FROM #TEMP1;

Answer 1

As requested in the comments, some possible solutions
I guess you're really looking for a function that can be CROSS APPLYed, something like
SELECT * FROM #Temp T
CROSS APPLY IsWKTValidFunc(T.WellKnownText, 4326) F
WHERE F.IsValid = <somecondition>
(Or even added to as computed column to give you a flag that's set on inserting your WKT)
Stored Proc
https://gis.stackexchange.com/questions/66642/detecting-invalid-wkt-in-text-column-in-sql-server has a simple SP that wraps GEOMETREY::STGeomFromText in a try catch block.
However, stored procs cannot be CROSS APPLYed (or called from a UDF that can be) so this would result in a cursor based solution.
UDF
A UDF can be cross applied, but can't have a TRY-CATCH block. You also can't call the above SP from a UDF. So not much use there.
CLR UDF
Wrap the GEOMETREY::STGeomFromText call in a CLR UDF that can be CROSS APPLIED, can have try catch and other error checking, rules etc, and return a flag indicating valid text. I haven't tried this one out but this sounds like the best option if CLR is enabled in your environment.
Hope this gives you some ideas. Feedback in the comments to these suggestions appreciated.