Adding hstore support. map[string]string will encode to hstores and throw errors on hstores with NULL values, and there is now a NullHstore type that is basically map[string]NullString and will both accept and decode NULL values properly

values.go

@@ -1,10 +1,12 @@
 package pgx
 
 import (
+	"bytes"
 	"encoding/hex"
 	"fmt"
 	"math"
 	"strconv"
+	"strings"
 	"time"
 	"unsafe"
 )
@@ -419,6 +421,81 @@ func (n NullTime) Encode(w *WriteBuf, oid Oid) error {
 	return encodeTimestampTz(w, n.Time)
 }
 
+// NullHstore represents an hstore that can be null or have null values
+// associated with its keys.  NullHstore implements the Scanner and TextEncoder
+// interfaces so it may be used both as an argument to Query[Row] and a
+// destination for Scan for prepared and unprepared queries.
+//
+// If Valid is false, then the value of the entire hstore column is NULL
+// If any of the NullString values in Store has Valid set to false, the key
+// appears in the hstore column, but its value is explicitly set to NULL
+type NullHstore struct {
+	Store map[string]NullString
+	Valid bool
+}
+
+func (h *NullHstore) Scan(vr *ValueReader) error {
+	//oid for hstore not standardized, so we check its type name
+	if vr.Type().DataTypeName != "hstore" {
+		vr.Fatal(ProtocolError(fmt.Sprintf("Cannot decode type %s into map[string]string", vr.Type().DataTypeName)))
+		return nil
+	}
+
+	if vr.Len() == -1 {
+		h.Valid = false
+		return nil
+	}
+
+	switch vr.Type().FormatCode {
+	case TextFormatCode:
+		store, err := parseHstoreToNullHstore(vr.ReadString(vr.Len()))
+		if err != nil {
+			vr.Fatal(ProtocolError(fmt.Sprintf("Can't decode hstore column: %v", err)))
+			return nil
+		}
+		h.Valid = true
+		h.Store = store
+		return nil
+	case BinaryFormatCode:
+		vr.Fatal(ProtocolError("Can't decode binary hstore"))
+		return nil
+	default:
+		vr.Fatal(ProtocolError(fmt.Sprintf("Unknown field description format code: %v", vr.Type().FormatCode)))
+		return nil
+	}
+}
+
+func (h NullHstore) FormatCode() int16 { return TextFormatCode }
+
+func (h NullHstore) Encode(w *WriteBuf, oid Oid) error {
+	var buf bytes.Buffer
+
+	if !h.Valid {
+		w.WriteInt32(-1)
+		return nil
+	}
+
+	i := 0
+	for k, v := range h.Store {
+		i++
+		ks := strings.Replace(k, `\`, `\\`, -1)
+		ks = strings.Replace(ks, `"`, `\"`, -1)
+		if v.Valid {
+			vs := strings.Replace(v.String, `\`, `\\`, -1)
+			vs = strings.Replace(vs, `"`, `\"`, -1)
+			buf.WriteString(fmt.Sprintf(`"%s"=>"%s"`, ks, vs))
+		} else {
+			buf.WriteString(fmt.Sprintf(`"%s"=>NULL`, ks))
+		}
+		if i < len(h.Store) {
+			buf.WriteString(", ")
+		}
+	}
+	w.WriteInt32(int32(buf.Len()))
+	w.WriteBytes(buf.Bytes())
+	return nil
+}
+
 func decodeBool(vr *ValueReader) bool {
 	if vr.Len() == -1 {
 		vr.Fatal(ProtocolError("Cannot decode null into bool"))
@@ -1045,6 +1122,60 @@ func encodeTimestamp(w *WriteBuf, value interface{}) error {
 	return encodeText(w, s)
 }
 
+func decodeHstore(vr *ValueReader) map[string]string {
+	//oid for hstore not standardized, so we check its type name
+	if vr.Type().DataTypeName != "hstore" {
+		vr.Fatal(ProtocolError(fmt.Sprintf("Cannot decode type %s into map[string]string", vr.Type().DataTypeName)))
+		return nil
+	}
+
+	if vr.Len() == -1 {
+		vr.Fatal(ProtocolError("Cannot decode null into map[string]string"))
+		return nil
+	}
+
+	switch vr.Type().FormatCode {
+	case TextFormatCode:
+		m, err := parseHstoreToMap(vr.ReadString(vr.Len()))
+		if err != nil {
+			vr.Fatal(ProtocolError(fmt.Sprintf("Can't decode hstore column: %v", err)))
+			return nil
+		}
+		return m
+	case BinaryFormatCode:
+		vr.Fatal(ProtocolError("Can't decode binary hstore"))
+		return nil
+	default:
+		vr.Fatal(ProtocolError(fmt.Sprintf("Unknown field description format code: %v", vr.Type().FormatCode)))
+		return nil
+	}
+}
+
+func encodeHstore(w *WriteBuf, value interface{}) error {
+	var buf bytes.Buffer
+
+	h, ok := value.(map[string]string)
+	if !ok {
+		return fmt.Errorf("Expected map[string]string, received %T", value)
+	}
+
+	i := 0
+	for k, v := range h {
+		i++
+		ks := strings.Replace(k, `\`, `\\`, -1)
+		ks = strings.Replace(ks, `"`, `\"`, -1)
+		vs := strings.Replace(v, `\`, `\\`, -1)
+		vs = strings.Replace(vs, `"`, `\"`, -1)
+		buf.WriteString(fmt.Sprintf(`"%s"=>"%s"`, ks, vs))
+		if i < len(h) {
+			buf.WriteString(", ")
+		}
+	}
+	w.WriteInt32(int32(buf.Len()))
+	w.WriteBytes(buf.Bytes())
+	return nil
+}
+
 func decode1dArrayHeader(vr *ValueReader) (length int32, err error) {
 	numDims := vr.ReadInt32()
 	if numDims == 0 {