ft: Add support for PFDEBUG command

internal/errors/errors.go

@@ -19,6 +19,7 @@ const (
 	WrongTypeErr           = "-WRONGTYPE Operation against a key holding the wrong kind of value"
 	WrongTypeHllErr        = "-WRONGTYPE Key is not a valid HyperLogLog string value."
 	InvalidHllErr          = "-INVALIDOBJ Corrupted HLL object detected"
+	HllEncodingErr         = "HLL encoding is not sparse"
 	WorkerNotFoundErr      = "worker with ID %s not found"
 	JSONPathValueTypeErr   = "-WRONGTYPE wrong type of path value - expected string but found integer"
 	HashValueNotIntegerErr = "hash value is not an integer"

internal/eval/commands.go

@@ -896,6 +896,13 @@ var (
 		Arity:    -2,
 		KeySpecs: KeySpecs{BeginIndex: 1},
 	}
+	pfDebugMeta = DiceCmdMeta{
+		Name:     "PFDEBUG",
+		Info:     `PFDEBUG subcommand key`,
+		Eval:     evalPFDEBUG,
+		Arity:    -3,
+		KeySpecs: KeySpecs{BeginIndex: 1},
+	}
 	pfCountCmdMeta = DiceCmdMeta{
 		Name: "PFCOUNT",
 		Info: `PFCOUNT key [key ...]
@@ -1188,6 +1195,7 @@ func init() {
 	DiceCmds["PFADD"] = pfAddCmdMeta
 	DiceCmds["PFCOUNT"] = pfCountCmdMeta
 	DiceCmds["PFMERGE"] = pfMergeCmdMeta
+	DiceCmds["PFDEBUG"] = pfDebugMeta
 	DiceCmds["PING"] = pingCmdMeta
 	DiceCmds["PTTL"] = pttlCmdMeta
 	DiceCmds["QUNWATCH"] = qUnwatchCmdMeta

internal/eval/eval.go

@@ -3,6 +3,7 @@ package eval
 import (
 	"bytes"
 	"crypto/rand"
+	"encoding/base64"
 
 	"errors"
 	"fmt"
@@ -12,6 +13,7 @@ import (
 	"math"
 	"math/big"
 	"math/bits"
+	"reflect"
 	"regexp"
 	"sort"
 	"strconv"
@@ -4108,6 +4110,91 @@ func evalPFMERGE(args []string, store *dstore.Store) []byte {
 	return clientio.RespOK
 }
 
+func evalPFDEBUG(args []string, store *dstore.Store) []byte {
+	if len(args) != 2 {
+		return diceerrors.NewErrArity("PFDEBUG")
+	}
+
+	subcommand := strings.ToUpper(args[0])
+	key := args[1]
+
+	obj := store.Get(key)
+	if obj == nil {
+		return diceerrors.NewErrWithMessage("Key does not exist")
+	}
+
+	hll, ok := obj.Value.(*hyperloglog.Sketch)
+	if !ok {
+		return diceerrors.NewErrWithMessage(diceerrors.WrongTypeHllErr)
+	}
+
+	sparseField := reflect.ValueOf(hll).Elem().FieldByName("sparseList")
+	sparseFieldValue := reflect.NewAt(sparseField.Type(), unsafe.Pointer(sparseField.UnsafeAddr())).Elem()
+
+	var encoding string
+	if sparseFieldValue.IsNil() {
+		encoding = "dense"
+	} else {
+		encoding = "sparse"
+	}
+
+	switch subcommand {
+	case "GETREG":
+		// For call to GETREG, encoding is converted from sparse to dense.
+		// We'll merge a sparse and an empty dense HLL to get a dense HLL
+		// with values of sparse HLL.
+		if encoding == "sparse" {
+			emptyDenseHLL := hyperloglog.NewNoSparse()
+			err := hll.Merge(emptyDenseHLL)
+
+			if err != nil {
+				return diceerrors.NewErrWithMessage(diceerrors.InvalidHllErr)
+			}
+		}
+
+		// registers := reflect.ValueOf(hll).Elem().FieldByName("regs")
+		// registersValue := reflect.NewAt(registers.Type(), unsafe.Pointer(registers.UnsafeAddr())).Elem()
+		data, error := hll.MarshalBinary()
+		if error != nil {
+			return diceerrors.NewErrWithMessage(diceerrors.InvalidHllErr)
+		}
+
+		return clientio.Encode(base64.StdEncoding.EncodeToString(data), false)
+
+	case "DECODE":
+		if encoding != "sparse" {
+			return diceerrors.NewErrWithMessage(diceerrors.HllEncodingErr)
+		}
+
+		data, err := hll.MarshalBinary()
+
+		if err != nil {
+			return diceerrors.NewErrWithMessage(diceerrors.InvalidHllErr)
+		}
+
+		return clientio.Encode(base64.StdEncoding.EncodeToString(data), false)
+
+	case "ENCODING":
+		return clientio.Encode(encoding, false)
+
+	case "TODENSE":
+		changed := 0
+		if encoding == "sparse" {
+			emptyDenseHLL := hyperloglog.NewNoSparse()
+			err := hll.Merge(emptyDenseHLL)
+			changed = 1
+
+			if err != nil {
+				return diceerrors.NewErrWithMessage(diceerrors.InvalidHllErr)
+			}
+		}
+		return clientio.Encode(changed, false)
+
+	default:
+		return diceerrors.NewErrWithMessage(fmt.Sprintf("Unknown PFDEBUG subcommand: %s", subcommand))
+	}
+}
+
 func evalJSONSTRLEN(args []string, store *dstore.Store) []byte {
 	if len(args) < 1 {
 		return diceerrors.NewErrArity("JSON.STRLEN")