  Based on the early-year observations from Neil Gehrels \emph{Swift}
Observatory, \cite{liang07} performed a systematic analysis for the shallow
decay component of gamma-ray bursts (GRBs) X-ray afterglow, in order to explore
its physical origin. Here we revisit the analysis with an updated sample (with
Swift/XRT GRBs between February 2004 and July 2017). We find that with a larger
sample, 1) the distributions of the characteristic properties of the shallow
decay phase (e.g. $t_{b}$ , $S_{X}$, $\Gamma_{X,1}$, and $\alpha_{X,1}$) still
accords with normal or lognormal distribution; 2) $\Gamma_{X,1}$ and
$\Gamma_{\gamma}$ still show no correlation, but the tentative correlations of
durations, energy fluences, and isotropic energies between the gamma-ray and
X-ray phases still exist; 3) for most GRBs, there is no significant spectral
evolution between the shallow decay segment and its follow-up segment, and the
latter is usually consistent with the external-shock models; 4) assuming that
the central engine has a power-law luminosity release history as
$L(t)=L_{0}(\frac{t}{t_{0}})^{-q}$, we find that the value $q$ is mainly
distributed between -0.5 and 0.5, with an average value of 0.16$\pm$ 0.12; 5)
the tentative correlation between $E_{\rm{iso},X}$ and $t'_{b}$ disappears, so
that the global 3-parameter correlation ($E_{\rm{iso},X}-E'_{p}-t'_{b}$)
becomes less significant; 6) the anti-correlation between $L_{X}$ and $t'_{b}$
and the three-parameter correlation ($E_{\rm{iso},\gamma}-L_{X}-t_{b}$) indeed
exist with a high confidence level. Overall, our results are generally
consistent with \cite{liang07}, confirming their suggestion that the shallow
decay segment in most bursts is consistent with an external forward shock
origin, probably due to a continuous energy injection from a long-lived central
engine.
