The client sends a Query packet to run a SQL command or query directly, i.e. without a prepared statement or cursor/portal.
String packetType: "Query"
String query : the text of the SQL command or query
String getQuery(): same as getting the query attribute directly, present for backward compatibility
void setQuery(String): same as setting the query attribute directly, present for backward compatibility
A common use of query filters is to reject or modify certain queries.