I am getting: No function matches the given name and argument types when executing poytgis function with psycopg2

Question

I am trying to execute a function which comes from an extension (postgis) with psycopg2.

import psycopg2

AFRICA = "africa"
ANTARCTICA = "antarctica"
ASIA = "asia"
AUSTRALIA_OCEANIA = "australia-oceania"
CENTRAL_AMERICA = "central-america"
EUROPE = "europe"
NORTH_AMERICA = "north-america"
SOUTH_AMERICA = "south-america"

SCHEMAS = [AFRICA, ANTARCTICA, ASIA, AUSTRALIA_OCEANIA,
           CENTRAL_AMERICA, EUROPE, NORTH_AMERICA, SOUTH_AMERICA]

def createCentroidTableFromPolygon(fromTable, toTable):
    return f"""
        CREATE TABLE IF NOT EXISTS {toTable} AS
        SELECT ST_Centroid(geom) AS geom, way_id, osm_type, name FROM {fromTable};
    """

for schema in SCHEMAS:    
    conn = psycopg2.connect(
        host='localhost',
        database='world',
        user="postgres",
        password="postgres",
        port=5432,
        options=f"-c search_path={schema}"
    )

    for i, table in enumerate(TABLES):
        # https://stackoverflow.com/questions/57116846/run-postgresql-functions-in-python-and-gets-error
        with conn:
            with conn.cursor() as cursor:
                # this works!
                cursor.execute(f"""SELECT * FROM {table} LIMIT 10""")
                print(cursor.fetchall())

                # this throws an error
                cursor.execute(createCentroidTableFromPolygon(
                table, FROM_POLY_TABLES[i]))

This gives me

psycopg2.errors.UndefinedFunction: function st_centroid(public.geometry) does not exist
LINE 3: SELECT ST_Centroid(geom) AS geom, way_id, osm_type, name…
HINT: No function matches the given name and argument types. You might need to add explicit type casts.

The extension postgis is installe on the database world though.

SELECT * FROM pg_extension;

When I try to run this function in pgAdmin, it works without a problem…

Asked By: four-eyes

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Source

Answer 1

This is the solution https://gis.stackexchange.com/questions/324386/psycopg2-programmingerror-function-does-not-exist

Andre Silva:

All calls to PostGIS functions must be schema qualified: schema_name.function (source).
To bypass writing the schema every time a PostGIS function is used, map the schema where PostGIS is (probably public) to the search_path (see here). As admin:

ALTER DATABASE <database_name> SET search_path TO schema1,schema2;

Moreover, make sure the private user has the necessary privileges in the database to proceed with the analysis (take a look here).

I solved it like this:

def createCentroidTableFromPolygon(fromTable, toTable):
    return f"""
    CREATE TABLE IF NOT EXISTS {toTable} AS
    SELECT public.ST_Centroid(geom) AS geom, way_id, osm_type, name FROM {fromTable};
    """

Answered By: four-eyes

I am getting: No function matches the given name and argument types when executing poytgis function with psycopg2

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