XX000: cache lookup failed for type 0 at Npgsql.NpgsqlConnector

Steps to reproduce

We run a stored procedure

CREATE OR REPLACE FUNCTION refresh_table(p_SearchTableName text, p_TableName text, p_IdType int) RETURNS BOOLEAN AS $$
DECLARE    
	drop_statement text;
	create_statement text;
	reporting_table text;
BEGIN
		
	-- remove special characters
	reporting_table :=  regexp_replace(lower(p_TableName), '[^a-z]+', '', 'g');

	drop_statement := 'DROP TABLE IF EXISTS ' || reporting_table || ' cascade';

	create_statement := 'CREATE UNLOGGED TABLE '|| reporting_table || ' (ID serial PRIMARY KEY, '
--... columns ...			
	')' ;


		EXECUTE drop_statement;				
		EXECUTE create_statement;
	RETURN TRUE;
END;
$$ LANGUAGE 'plpgsql'
 SECURITY DEFINER;

then using the same connection we call conn.ReloadTypes();

after that we open a new connection just to be sure and also call conn.ReloadTypes() in case its part of a connection pool and the connection has types cached.

	using (var conn = new NpgsqlConnection(connectionString)) {
				conn.Open();
				//https://stackoverflow.com/questions/51086421/npgsql-postgresexception-0x80004005-xx000-cache-lookup-failed-for-type-20785
				conn.ReloadTypes();
using (var cmd = new NpgsqlCommand(insertSQL, conn)) {
// insert stuff..
...
cmd.ExecuteNonQuery();
// exception thrown here

The issue

Exception thrown: XX000: cache lookup failed for type 0

If you are seeing an exception, include the full exceptions details (message and stack trace).

Exception message:
Stack trace:
XX000: cache lookup failed for type 0 at Npgsql.NpgsqlConnector.<>c__DisplayClass160_0.<<DoReadMessage>g__ReadMessageLong|0>d.MoveNext() --- End of stack trace from previous location where exception was thrown --- 
at Npgsql.NpgsqlDataReader.NextResult(Boolean async, Boolean isConsuming) 
at Npgsql.NpgsqlDataReader.NextResult() at Npgsql.NpgsqlCommand.ExecuteReaderAsync(CommandBehavior behavior, Boolean async, CancellationToken cancellationToken) at Npgsql.NpgsqlCommand.ExecuteNonQuery(Boolean async, CancellationToken cancellationToken) 
at Npgsql.NpgsqlCommand.ExecuteNonQuery() 
at ReportPublisher.PublishEntityTypeAsync[TEntityType,TEntity](String typeName, String type, TEntityType entityType, MiddlewareClient cl, IList`1 entityMeta, CancellationToken cancellationToken)
 or

 Npgsql.PostgresException : XX000: cache lookup failed for type 0at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
 at async Npgsql.NpgsqlConnector.<>c__DisplayClass160_0.<DoReadMessage>g__ReadMessageLong|0(??)
 at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
 at async Npgsql.NpgsqlDataReader.NextResult(??)
 at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
 at Npgsql.NpgsqlDataReader.NextResult()
 at async Npgsql.NpgsqlCommand.ExecuteReaderAsync(??)
 at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
 at async Npgsql.NpgsqlCommand.ExecuteNonQuery(??)
 at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
 at Npgsql.NpgsqlCommand.ExecuteNonQuery()
 at async ReportPublisher.PublishEntityTypeAsync[TEntityType,TEntity](String typeName,String type,TEntityType entityType,MiddlewareClient cl,IList`1 entityMeta,CancellationToken cancellationToken)

### Further technical details

Npgsql version: 5.0.3
PostgreSQL version: PostgreSQL 10.11, compiled by Visual C++ build 1800, 64-bit
Operating system: Windows Server 2019 (azure)

Other details about my project setup:
The code is running in an azure function, so there would be connection pooling.

[vonzshik]

@vllama I did attempt to reproduce the error with the code you’ve provided, but so far no good. Is it possible to make a repro?

[roji]

Closing as no repro was provided.