Why is my Go database/sql Query Significantly Slower Than a Direct Postgres psql Query?

Querying Using database/sql Significantly Slower Than Querying the Database Directly

Despite using identical queries, there is a noticeable performance discrepancy between executing a query directly using Postgres' psql utility and using the database/sql package in a Go application. This discrepancy, where queries that take milliseconds in psql take tens of milliseconds in Go, could be attributed to specific factors in the implementation.

Understanding database/sql Connections

database/sql initializes a connection pool for establishing connections to the database, rather than creating a single connection. The initial delay in query execution in database/sql is because the pool begins with zero open connections. The first query must establish a connection to the server before executing the SQL statement.

Subsequent queries also face delays as the connection from the first query has not been released back to the pool. This means that each subsequent query needs to create a new connection before executing the query.

Releasing Connections Back to the Pool

To resolve the performance discrepancy, ensure that connections are released back to the pool after each query. Releasing a connection involves retaining the primary return value of db.Query and subsequently calling the Close method on it.

Initializing the Pool with an Open Connection

To mitigate the initial delay, call Ping on the connection pool immediately after initialization. This ensures that at least one connection is available in the pool.

Prepared Statements

Although simple queries without arguments are executed as expected, queries with arguments in database/sql actually create and execute prepared statements under the hood. Prepared statements offer performance benefits when executing the same query multiple times with different arguments.

Addressing Additional Latency

Besides connection management and prepared statements, there may be additional latency factors to consider:

• Network latency: The delay caused by data transfer over the network between the application and the database.
• Server load: The database server's workload can affect query execution times.

By addressing these factors and implementing the recommendations provided, the performance of queries using database/sql can be significantly improved, making it comparable to querying the database directly.

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