CopyFrom had to create a prepared statement to get the OIDs of the data
types that were going to be copied into the table. Every COPY operation
required an extra round trips to retrieve the type information. There
was no way to customize this behavior.
By leveraging the QueryExecMode feature, like in `Conn.Query`, users can
specify if they want to cache the prepared statements, execute
them on every request (like the old behavior), or bypass the prepared
statement relying on the pgtype.Map to get the type information.
The `QueryExecMode` behave exactly like in `Conn.Query` in the way the
data type OIDs are fetched, meaning that:
- `QueryExecModeCacheStatement`: caches the statement.
- `QueryExecModeCacheDescribe`: caches the statement and assumes they do
not change.
- `QueryExecModeDescribeExec`: gets the statement description on every
execution. This is like to the old behavior of `CopyFrom`.
- `QueryExecModeExec` and `QueryExecModeSimpleProtocol`: maintain the
same behavior as before, which is the same as `QueryExecModeDescribeExec`.
It will keep getting the statement description on every execution
The `QueryExecMode` can only be set via
`ConnConfig.DefaultQueryExecMode`, unlike `Conn.Query` there's no
support for specifying the `QueryExecMode` via optional arguments
in the function signature.
Allows Tracelog to log the Prepare queiries.
Fixes#1383
Unit tests:
* added logger.Clear method to cleanup old log messages
* added logger.FilterByMsg to get only specific logs for assertions. When quieries are executed using different query exec methods prepare query can be not executed. So we can get different number of logs using different exec methods.
Alejandro Do Nascimento Mora
Vitalii Solodilov
Jack Christensen