[postgis-users] PostGIS and prepared statement, data_type problem

[Marco Boeringa]

Hi all,

Reading this PostgreSQL page about prepared SQL statements:

https://www.postgresql.org/docs/current/sql-prepare.html

it suggests that 'data_type' is optional, and "will be inferred from the 
context in which the parameter is first referenced" if unspecified.

Now I have attempted to create a prepared SQL statement for doing 
INSERTs, which includes an "ST_GeometryFromText()" function call that 
will get WKT inserted in the geometry field of the target table.

However, this fails with a "could not determine data type of parameter 
$1" error for the geometry field.

Is there something PostGIS functions do not expose to PostgreSQL that 
causes PostgreSQL to fail to "infer from context" the field type? Or is 
this a general issue with PREPAREd statements if they include any 
function call, whether PostGIS or core PostgreSQL, and are you always 
required to specify data type in this context?

Marco