Method buildCopyBuf

copy_from.go:217–255

(buf []byte, sd *pgconn.StatementDescription)

}

func (ct *copyFrom) buildCopyBuf(buf []byte, sd *pgconn.StatementDescription) (bool, []byte, error) {
	const sendBufSize = 65536 - 5 // The packet has a 5-byte header
	lastBufLen := 0
	largestRowLen := 0

	for ct.rowSrc.Next() {
		lastBufLen = len(buf)

		values, err := ct.rowSrc.Values()
		if err != nil {
			return false, nil, err
		}
		if len(values) != len(ct.columnNames) {
			return false, nil, fmt.Errorf("expected %d values, got %d values", len(ct.columnNames), len(values))
		}

		buf = pgio.AppendInt16(buf, int16(len(ct.columnNames)))
		for i, val := range values {
			buf, err = encodeCopyValue(ct.conn.typeMap, buf, sd.Fields[i].DataTypeOID, val)
			if err != nil {
				return false, nil, err
			}
		}

		rowLen := len(buf) - lastBufLen
		if rowLen > largestRowLen {
			largestRowLen = rowLen
		}

		// Try not to overflow size of the buffer PgConn.CopyFrom will be reading into. If that happens then the nature of
		// io.Pipe means that the next Read will be short. This can lead to pathological send sizes such as 65531, 13, 65531
		// 13, 65531, 13, 65531, 13.
		if len(buf) > sendBufSize-largestRowLen {
			return true, buf, nil
		}
	}

	return false, buf, nil
}

// CopyFrom uses the PostgreSQL copy protocol to perform bulk data insertion. It returns the number of rows copied and
// an error.