# 5.4.1 (June 18, 2023)

* Fix: concurrency bug with pgtypeDefaultMap and simple protocol (Lev Zakharov)
* Add TxOptions.BeginQuery to allow overriding the default BEGIN query

# 5.4.0 (June 14, 2023)

* Replace platform specific syscalls for non-blocking IO with more traditional goroutines and deadlines. This returns to the v4 approach with some additional improvements and fixes. This restores the ability to use a pgx.Conn over an ssh.Conn as well as other non-TCP or Unix socket connections. In addition, it is a significantly simpler implementation that is less likely to have cross platform issues.
* Optimization: The default type registrations are now shared among all connections. This saves about 100KB of memory per connection. `pgtype.Type` and `pgtype.Codec` values are now required to be immutable after registration. This was already necessary in most cases but wasn't documented until now. (Lev Zakharov)
* Fix: Ensure pgxpool.Pool.QueryRow.Scan releases connection on panic
* CancelRequest: don't try to read the reply (Nicola Murino)
* Fix: correctly handle bool type aliases (Wichert Akkerman)
* Fix: pgconn.CancelRequest: Fix unix sockets: don't use RemoteAddr()
* Fix: pgx.Conn memory leak with prepared statement caching (Evan Jones)
* Add BeforeClose to pgxpool.Pool (Evan Cordell)
* Fix: various hstore fixes and optimizations (Evan Jones)
* Fix: RowToStructByPos with embedded unexported struct
* Support different bool string representations (Lev Zakharov)
* Fix: error when using BatchResults.Exec on a select that returns an error after some rows.
* Fix: pipelineBatchResults.Exec() not returning error from ResultReader
* Fix: pipeline batch results not closing pipeline when error occurs while reading directly from results instead of using
    a callback.
* Fix: scanning a table type into a struct
* Fix: scan array of record to pointer to slice of struct
* Fix: handle null for json (Cemre Mengu)
* Batch Query callback is called even when there is an error
* Add RowTo(AddrOf)StructByNameLax (Audi P. Risa P)

# 5.3.1 (February 27, 2023)

* Fix: Support v4 and v5 stdlib in same program (Tomáš Procházka)
* Fix: sql.Scanner not being used in certain cases
* Add text format jsonpath support
* Fix: fake non-blocking read adaptive wait time

# 5.3.0 (February 11, 2023)

* Fix: json values work with sql.Scanner
* Fixed / improved error messages (Mark Chambers and Yevgeny Pats)
* Fix: support scan into single dimensional arrays
* Fix: MaxConnLifetimeJitter setting actually jitter (Ben Weintraub)
* Fix: driver.Value representation of bytea should be []byte not string
* Fix: better handling of unregistered OIDs
* CopyFrom can use query cache to avoid extra round trip to get OIDs (Alejandro Do Nascimento Mora)
* Fix: encode to json ignoring driver.Valuer
* Support sql.Scanner on renamed base type
* Fix: pgtype.Numeric text encoding of negative numbers (Mark Chambers)
* Fix: connect with multiple hostnames when one can't be resolved
* Upgrade puddle to remove dependency on uber/atomic and fix alignment issue on 32-bit platform
* Fix: scanning json column into **string
* Multiple reductions in memory allocations
* Fake non-blocking read adapts its max wait time
* Improve CopyFrom performance and reduce memory usage
* Fix: encode []any to array
* Fix: LoadType for composite with dropped attributes (Felix Röhrich)
* Support v4 and v5 stdlib in same program
* Fix: text format array decoding with string of "NULL"
* Prefer binary format for arrays

# 5.2.0 (December 5, 2022)

* `tracelog.TraceLog` implements the pgx.PrepareTracer interface. (Vitalii Solodilov)
* Optimize creating begin transaction SQL string (Petr Evdokimov and ksco)
* `Conn.LoadType` supports range and multirange types (Vitalii Solodilov)
* Fix scan `uint` and `uint64` `ScanNumeric`. This resolves a PostgreSQL `numeric` being incorrectly scanned into `uint` and `uint64`.

# 5.1.1 (November 17, 2022)

* Fix simple query sanitizer where query text contains a Unicode replacement character.
* Remove erroneous `name` argument from `DeallocateAll()`. Technically, this is a breaking change, but given that method was only added 5 days ago this change was accepted. (Bodo Kaiser)

# 5.1.0 (November 12, 2022)

* Update puddle to v2.1.2. This resolves a race condition and a deadlock in pgxpool.
* `QueryRewriter.RewriteQuery` now returns an error. Technically, this is a breaking change for any external implementers, but given the minimal likelihood that there are actually any external implementers this change was accepted.
* Expose `GetSSLPassword` support to pgx.
* Fix encode `ErrorResponse` unknown field handling. This would only affect pgproto3 being used directly as a proxy with a non-PostgreSQL server that included additional error fields.
* Fix date text format encoding with 5 digit years.
* Fix date values passed to a `sql.Scanner` as `string` instead of `time.Time`.
* DateCodec.DecodeValue can return `pgtype.InfinityModifier` instead of `string` for infinite values. This now matches the behavior of the timestamp types.
* Add domain type support to `Conn.LoadType()`.
* Add `RowToStructByName` and `RowToAddrOfStructByName`. (Pavlo Golub)
* Add `Conn.DeallocateAll()` to clear all prepared statements including the statement cache. (Bodo Kaiser)

# 5.0.4 (October 24, 2022)

* Fix: CollectOneRow prefers PostgreSQL error over pgx.ErrorNoRows
* Fix: some reflect Kind checks to first check for nil
* Bump golang.org/x/text dependency to placate snyk
* Fix: RowToStructByPos on structs with multiple anonymous sub-structs (Baptiste Fontaine)
* Fix: Exec checks if tx is closed

# 5.0.3 (October 14, 2022)

* Fix `driver.Valuer` handling edge cases that could cause infinite loop or crash

# v5.0.2 (October 8, 2022)

* Fix date encoding in text format to always use 2 digits for month and day
* Prefer driver.Valuer over wrap plans when encoding
* Fix scan to pointer to pointer to renamed type
* Allow scanning NULL even if PG and Go types are incompatible

# v5.0.1 (September 24, 2022)

* Fix 32-bit atomic usage
* Add MarshalJSON for Float8 (yogipristiawan)
* Add `[` and `]` to text encoding of `Lseg`
* Fix sqlScannerWrapper NULL handling

# v5.0.0 (September 17, 2022)

## 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.

Previously, a type that implemented `driver.Valuer` would have the `Value` method called even on a nil pointer. All nils
whether typed or untyped now represent `NULL`.

### 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](https://github.com/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 https://github.com/shopspring/decimal and https://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.
* `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.
