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pgx v5.0.0 Release Notes

Release Date: 2022-09-17 // over 1 year ago

  • 📦 Merged Packages

    github.com/jackc/pgtype, github.com/jackc/pgconn, and github.com/jackc/pgproto3 are now included in the main github.com/jackc/pgx repository. Previously there was confusion as to where issues should be reported, additional 🚀 release work due to releasing multiple packages, and less clear changelogs.

    pgconn

    CommandTag is now an opaque type instead of directly exposing an underlying []byte.

    The return value ResultReader.Values() is no longer safe to retain a reference to after a subsequent call to NextRow() or Close().

    Trace() method adds low level message tracing similar to the PQtrace function in libpq.

    pgconn now uses non-blocking IO. This is a significant internal restructuring, but it should not cause any visible changes on its own. However, it is important in implementing other new features.

    CheckConn() checks a connection's liveness by doing a non-blocking read. This can be used to detect database restarts or network interruptions without executing a query or a ping.

    👍 pgconn now supports pipeline mode.

    🚚 *PgConn.ReceiveResults removed. Use pipeline mode instead.

    ⏱ Timeout() no longer considers context.Canceled as a timeout error. context.DeadlineExceeded still is considered a timeout error.

    pgxpool

    🚚 Connect and ConnectConfig have been renamed to New and NewWithConfig respectively. The LazyConnect option has been removed. Pools always lazily connect.

    pgtype

    📦 The pgtype package has been significantly changed.

    NULL Representation

    Previously, types had a Status field that could be Undefined, Null, or Present. This has been changed to a Valid bool field to harmonize with how database/sql represents NULL and to make the zero value useable.

    Codec and Value Split

    Previously, the type system combined decoding and encoding values with the value types. e.g. Type Int8 both handled encoding and decoding the PostgreSQL representation and acted as a value object. This caused some difficulties when there was not an exact 1 to 1 relationship between the Go types and the PostgreSQL types For example, scanning a 👀 PostgreSQL binary numeric into a Go float64 was awkward (see https://github.com/jackc/pgtype/issues/147). This concepts have been separated. A Codec only has responsibility for encoding and decoding values. Value types are generally defined by implementing an interface that a particular Codec understands (e.g. PointScanner and PointValuer for the PostgreSQL point type).

    Array Types

    All array types are now handled by ArrayCodec instead of using code generation for each new array type. This also 👍 means that less common array types such as point[] are now supported. Array[T] supports PostgreSQL multi-dimensional arrays.

    Composite Types

    Composite types must be registered before use. CompositeFields may still be used to construct and destruct composite values, but any type may now implement CompositeIndexGetter and CompositeIndexScanner to be used as a composite.

    Range Types

    Range types are now handled with types RangeCodec and Range[T]. This allows additional user defined range types to easily be handled. Multirange types are handled similarly with MultirangeCodec and Multirange[T].

    pgxtype

    🚚 LoadDataType moved to *Conn as LoadType.

    Bytea

    The Bytea and GenericBinary types have been replaced. Use the following instead:

    • []byte - For normal usage directly use []byte.
    • DriverBytes - Uses driver memory only available until next database method call. Avoids a copy and an allocation.
    • PreallocBytes - Uses preallocated byte slice to avoid an allocation.
    • UndecodedBytes - Avoids any decoding. Allows working with raw bytes.

    ⬇️ Dropped lib/pq Support

    ✅ pgtype previously supported and was tested against lib/pq. While it will continue to work 👍 in most cases this is no longer supported.

    database/sql Scan

    Previously, most Scan implementations would convert []byte to string automatically to decode a text value. Now 👍 only string is handled. This is to allow the possibility of future binary support in database/sql mode by considering []byte to be binary format and string text format. This change should have no effect for any use with pgx. The previous behavior was only necessary for lib/pq compatibility.

    ➕ Added *Map.SQLScanner to create a sql.Scanner for types such as []int32 and Range[T] that do not implement sql.Scanner directly.

    Number Type Fields Include Bit size

    Int2, Int4, Int8, Float4, Float8, and Uint32 fields now include bit size. e.g. Int is renamed to Int64. This matches the convention set by database/sql. In addition, for comparable types like pgtype.Int8 and 👕 sql.NullInt64 the structures are identical. This means they can be directly converted one to another.

    3rd Party Type Integrations

    Other Changes

    • Bit and Varbit are both replaced by the Bits type.
    • CID, OID, OIDValue, and XID are replaced by the Uint32 type.
    • Hstore is now defined as map[string]*string.
    • 🚚 JSON and JSONB types removed. Use []byte or string directly.
    • 🚚 QChar type removed. Use rune or byte directly.
    • 🚚 Inet and Cidr types removed. Use netip.Addr and netip.Prefix directly. These types are more memory efficient than the previous net.IPNet.
    • 🚚 Macaddr type removed. Use net.HardwareAddr directly.
    • 📇 Renamed pgtype.ConnInfo to pgtype.Map.
    • 📇 Renamed pgtype.DataType to pgtype.Type.
    • 📇 Renamed pgtype.None to pgtype.Finite.
    • RegisterType now accepts a *Type instead of Type.
    • Assorted array helper methods and types made private.

    stdlib

    • ✂ Removed AcquireConn and ReleaseConn as that functionality has been built in since Go 1.13.

    ⬇️ Reduced Memory Usage by Reusing Read Buffers

    Previously, the connection read buffer would allocate large chunks of memory and never reuse them. This allowed transferring ownership to anything such as scanned values without incurring an additional allocation and memory copy. 📌 However, this came at the cost of overall increased memory allocation size. But worse it was also possible to pin large chunks of memory by retaining a reference to a small value that originally came directly from the read buffer. Now ownership remains with the read buffer and anything needing to retain a value must make a copy.

    Query Execution Modes

    Control over automatic prepared statement caching and simple protocol use are now combined into query execution mode. 📚 See documentation for QueryExecMode.

    QueryRewriter Interface and NamedArgs

    👍 pgx now supports named arguments with the NamedArgs type. This is implemented via the new QueryRewriter interface which 👍 allows arbitrary rewriting of query SQL and arguments.

    RowScanner Interface

    The RowScanner interface allows a single argument to Rows.Scan to scan the entire row.

    Rows Result Helpers

    • CollectRows and RowTo* functions simplify collecting results into a slice.
    • CollectOneRow collects one row using RowTo* functions.
    • ForEachRow simplifies scanning each row and executing code using the scanned values. ForEachRow replaces QueryFunc.

    Tx Helpers

    Rather than every type that implemented Begin or BeginTx methods also needing to implement BeginFunc and BeginTxFunc these methods have been converted to functions that take a db that implements Begin or BeginTx.

    👌 Improved Batch Query Ergonomics

    🏗 Previously, the code for building a batch went in one place before the call to SendBatch, and the code for reading the results went in one place after the call to SendBatch. This could make it difficult to match up the query and the code to handle the results. Now Queue returns a QueuedQuery which has methods Query, QueryRow, and Exec which can be used to register a callback function that will handle the result. Callback functions are called automatically when BatchResults.Close is called.

    SendBatch Uses Pipeline Mode When Appropriate

    Previously, a batch with 10 unique parameterized statements executed 100 times would entail 11 network round trips. 1 for each prepare / describe and 1 for executing them all. Now pipeline mode is used to prepare / describe all statements in a single network round trip. So it would only take 2 round trips.

    🌲 Tracing and Logging

    📦 Internal logging support has been replaced with tracing hooks. This allows custom tracing integration with tools like OpenTelemetry. Package tracelog provides an adapter for pgx v4 loggers to act as a tracer.

    All integrations with 3rd party loggers have been extracted to separate repositories. This trims the pgx dependency tree.