pgx/CHANGELOG.md

Unreleased v5

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.

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.

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 significantly reduced the amount of code and the compiled binary size. 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

load data type moved to conn

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

• Extracted integrations with github.com/shopspring/decimal and github.com/gofrs/uuid to https://github.com/jackc/pgx-shopspring-decimal and https://github.com/jackc/pgx-gofrs-uuid respectively. This trims the pgx dependency tree.

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.
• 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.

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.

3rd Party Logger Integration

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