How is a pgfplotstable table stored internally?

Question

I'm writing some lua code that outputs a table saved to a file that is then read by \pgfplotstableread{myfile.dat}\mytable. I'd like to avoid two steps: saving to a file and reading with \pgfplotstableread. So, my option is to "write" directly \mytable on lua side. But I don't know how tables are stored internally by pgfplotstable. I did some experiment:

\documentclass{article}
\usepackage{pgfplotstable}

\pgfplotstableread[col sep=comma]{
Name, Age, stDev
Adam, 15, 3
Eve, 12, 1
}\mytable

\begin{document}

\show\mytable

\end{document}

This results in:

> \mytable=macro:
->\pgfpl@@ {Name}\pgfpl@@ {Age}\pgfpl@@ {stDev}.

So I guess the other lines are stored in other macros. My question is how?

Answer 1

According to the comments in pgfplotstableshared.code.tex (line 31-53)

% This file provides a high-level table manipulation and typesetting
% package.
%
%
% ---------------------------------------------
%  Implementation notes for programmers:
% ---------------------------------------------
%
%  The table data structure consists of
%  1. A name which must be a valid TeX macro like '\table'
%  2. A column list in the \pgfplotslist format.
%   In fact, the column list is stored in the table's name:
%     \pgfplotslistnewempty\table
%  3. A "file name" stored in
%     \csname\string<\namemacro>@@table@name\endcsname
%  4. A "scan line length" number stored in
%         \csname\string<\namemacro>@@table@scanline\endcsname
%         It contains the value of \pgfplotsscanlinelength which has
%         been identified right after \pgfplotstableread.
%  5. foreach column, there is a list of row-values (a row-vector) in
%  the \pgfplotslist format named
%         \csname\string<\namemacro>@<column name>\endcsname
%

we can write the following test

\documentclass{article}
\usepackage{pgfplotstable}
\pgfplotstableread[col sep=comma]{
Name, Age, stDev
Adam, 15, 3
Eve, 12, 1
}\mytable

\begin{document}
\begin{itemize}\makeatletter\ttfamily

\item[2] \string\mytable \\
\meaning\mytable

\item[3] file name \\
\expandafter\meaning\csname\string\mytable @@table@name\endcsname

\item[4] scan line length \\
\expandafter\meaning\csname\string\mytable @@table@scanline\endcsname

\item[5] column Name \\
\expandafter\meaning\csname\string\mytable @Name\endcsname

\item[5] column Age \\
\expandafter\meaning\csname\string\mytable @Age\endcsname

\item[5] column stDev \\
\expandafter\meaning\csname\string\mytable @stDev\endcsname

\end{itemize}
\end{document}

This gives us