readerWg   sync.WaitGroup
}

// Read - reads single record.
func (r *Reader) Read(dst sql.Record) (sql.Record, error) {
	v, ok := <-r.decoded
	if !ok {
		if r.err != nil && *r.err != nil {
			return nil, errJSONParsingError(*r.err)
		}
		return nil, io.EOF
	}
	dstRec, ok := dst.(*Record)
	if !ok {
		dstRec = &Record{}
	}
	dstRec.object = v
	return dstRec, nil
}

// Close - closes underlying reader.

//
//	// Now, we need an io.Reader that can access
//	// the ETag computed over the content.
//	reader := etag.Wrap(encryptedContent, content)
func Wrap(wrapped, content io.Reader) io.Reader {
	if t, ok := content.(Tagger); ok {
		return wrapReader{
			Reader: wrapped,
			Tagger: t,
		}
	}
	return wrapReader{
		Reader: wrapped,
	}
}

// A Reader wraps an io.Reader and computes the

	if beginner, ok := db.ConnPool.(TxBeginner); ok {
		tx, err := beginner.BeginTx(ctx, opt)
		return &PreparedStmtTX{PreparedStmtDB: db, Tx: tx}, err
	}

	beginner, ok := db.ConnPool.(ConnPoolBeginner)
	if !ok {
		return nil, ErrInvalidTransaction
	}

	connPool, err := beginner.BeginTx(ctx, opt)
	if err != nil {
		return nil, err
	}
	if tx, ok := connPool.(Tx); ok {

		builder.WriteString(" HAVING ")
		Where{Exprs: groupBy.Having}.Build(builder)
	}
}

// MergeClause merge group by clause
func (groupBy GroupBy) MergeClause(clause *Clause) {
	if v, ok := clause.Expression.(GroupBy); ok {
		copiedColumns := make([]Column, len(v.Columns))
		copy(copiedColumns, v.Columns)
		groupBy.Columns = append(copiedColumns, groupBy.Columns...)

		copiedHaving := make([]Expression, len(v.Having))

	if globalEndpoints.Legacy() {
		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrNotImplemented), r.URL)
		return
	}

	z, ok := objectAPI.(*erasureServerPools)
	if !ok || len(z.serverPools) == 1 {
		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrNotImplemented), r.URL)
		return
	}

	if z.IsDecommissionRunning() {

// present.
func kmsKeyIDFromMetadata(metadata map[string]string) string {
	const ARNPrefix = crypto.ARNPrefix
	if len(metadata) == 0 {
		return ""
	}
	kmsID, ok := metadata[crypto.MetaKeyID]
	if !ok {
		return ""
	}
	if strings.HasPrefix(kmsID, ARNPrefix) {
		return kmsID
	}
	return ARNPrefix + kmsID
}

// DecryptETags decryptes the ETag of all ObjectInfos using the KMS.
//

	if err := m.send(msg); err != nil {
		return nil, err
	}
	if debugReqs {
		fmt.Println(m.MuxID, m.parent.String(), "SEND")
	}
	// Wait for response or context.
	select {
	case v, ok := <-ch:
		if !ok {
			return nil, ErrDisconnected
		}
		if debugReqs && v.Err != nil {
			v.Err = fmt.Errorf("%d %s RESP ERR: %w", m.MuxID, m.parent.String(), v.Err)
		}
		return v.Msg, v.Err
	case <-ctx.Done():

		for tgt := range tgtKV {
			ckvs := c[subSys][tgt]
			for _, kv := range cp[subSys][Default] {
				_, ok := c[subSys][tgt].Lookup(kv.Key)
				if !ok {
					ckvs.Set(kv.Key, kv.Value)
				}
			}
			if _, ok := cp[subSys]; !ok {
				rnSubSys, ok := renamedSubsys[subSys]
				if !ok {
					// A config subsystem was removed or server was downgraded.
					continue
				}

	default:
		err = sys.store.LoadUser(ctx, accessKey)
		loadUserCalled = true
	}

	u, ok = sys.store.GetUser(accessKey)
	if !ok && !loadUserCalled {
		err = sys.store.LoadUser(ctx, accessKey)
		loadUserCalled = true

		u, ok = sys.store.GetUser(accessKey)
	}

	if !ok && loadUserCalled && err != nil {
		iamLogOnceIf(ctx, err, accessKey)

		// return 503 to application

		if collPath.isDescendantOf(path) {
			if v, ok := h.metricsData.mgMap[collPath]; ok {
				matchingMG[collPath] = v
			} else if v, ok := h.metricsData.bucketMGMap[collPath]; ok {
				matchingMG[collPath] = v
			}
		}
	}

	if len(matchingMG) == 0 {
		return nil
	}

	var metrics []metricDisplay
	for _, collectorPath := range h.metricsData.collectorPaths {
		if mg, ok := matchingMG[collectorPath]; ok {