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* Documented the `--query' operation.

This commit is contained in:
Eelco Dolstra 2003-08-13 10:45:01 +00:00
parent b4f88d0ec3
commit c34a153ae5
3 changed files with 232 additions and 2 deletions
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17
doc/manual/bugs.xml
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@ -15,6 +15,23 @@
</para>
</listitem>
<listitem>
<para>
Unify the concepts of successors and substitutes into a general notion
of <emphasis>equivalent expressions</emphasis>. Expressions are
equivalent if they have the same target paths with the same
identifiers. However, even though they are functionally equivalent,
they may differ stronly with respect to their <emphasis>performance
characteristics</emphasis>. For example, realising a slice is more
efficient that realising the derivation from which that slice was
produced. On the other hand, distributing sources may be more
efficient (storage- or bandwidth-wise) than distributing binaries. So
we need to be able to attach weigths or priorities or performance
annotations to expressions; Nix can then choose the most efficient
expression dependent on the context.
</para>
</listitem>
</itemizedlist>
</appendix>

214
doc/manual/nix-reference.xml
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@ -126,6 +126,8 @@
</refsect1>
<!--######################################################################-->
<refsect1>
<title>Operation <option>--install</option></title>
@ -162,6 +164,8 @@
</refsect1>
<!--######################################################################-->
<refsect1>
<title>Operation <option>--delete</option></title>
@ -203,6 +207,216 @@
</refsect1>
<!--######################################################################-->
<refsect1>
<title>Operation <option>--query</option></title>
<refsect2>
<title>Synopsis</title>
<cmdsynopsis>
<command>nix</command>
<group>
<arg><option>--query</option></arg>
<arg><option>-q</option></arg>
</group>
<group>
<group>
<arg><option>--list</option></arg>
<arg><option>-l</option></arg>
</group>
<group>
<arg><option>--requisites</option></arg>
<arg><option>-r</option></arg>
</group>
<group>
<arg><option>--expansion</option></arg>
<arg><option>-e</option></arg>
</group>
<group>
<arg><option>--graph</option></arg>
<arg><option>-g</option></arg>
</group>
</group>
<arg choice='plain' rep='repeat'><replaceable>args</replaceable></arg>
</cmdsynopsis>
</refsect2>
<refsect2>
<title>Description</title>
<para>
The operation <option>--query</option> displays various bits of
information about Nix expressions or paths in the store. The queries
are described in <xref linkend='nixref-queries' />. At most one query
can be specified; the default query is <option>--list</option>.
</para>
</refsect2>
<refsect2 id='nixref-queries'>
<title>Queries</title>
<variablelist>
<varlistentry>
<term><option>--list</option></term>
<listitem>
<para>
Prints out the target paths of the Nix expressions indicated by
the identifiers <replaceable>args</replaceable>. In the case of
a derivation expression, these are the paths that will be
produced by the builder of the expression. In the case of a
slice expression, these are the root paths (which are generally
the paths that were produced by the builder of the derivation
expression of which the slice is a normal form).
</para>
<para>
This query has one option:
</para>
<variablelist>
<varlistentry>
<term><option>--normalise</option></term>
<listitem>
<para>
Causes the target paths of the <emphasis>normal
forms</emphasis> of the expressions to be printed, rather
than the target paths of the expressions themselves.
</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--requisites</option></term>
<listitem>
<para>
Prints out the requisite paths of the Nix expressions indicated
by the identifiers <replaceable>args</replaceable>. The
requisite paths of a Nix expression are the paths that need to be
present in the system to be able to realise the expression. That
is, they form the <emphasis>closure</emphasis> of the expression
in the file system (i.e., no path in the set of requisite paths
points to anything outside the set of requisite paths).
</para>
<para>
The notion of requisite paths is very useful when one wants to
distribute Nix expressions. Since they form a closure, they are
the only paths one needs to distribute to another system to be
able to realise the expression on the other system.
</para>
<para>
This query is generally used to implement various kinds of
distribution. A <emphasis>source distribution</emphasis> is
obtained by distributing the requisite paths of a derivation
expression. A <emphasis>binary distribution</emphasis> is
obtained by distributing the requisite paths of a slice
expression (i.e., the normal form of a derivation expression; you
can directly specify the identifier of the slice expression, or
use <option>--normalise</option> and specify the identifier of a
derivation expression). A <emphasis>cache
distribution</emphasis> is obtained by distributing the
requisite paths of a derivation expression and specifying the
option <option>--include-successors</option>. This will include
not just the paths of a source and binary distribution, but also
all expressions and paths of subterms of the source. This is
useful if one wants to realise on the target system a Nix
expression that is similar but not quite the same as the one
being distributed, since any common subterms will be reused.
</para>
<para>
This query has a number of options:
</para>
<variablelist>
<varlistentry>
<term><option>--normalise</option></term>
<listitem>
<para>
Causes the requisite paths of the <emphasis>normal
forms</emphasis> of the expressions to be printed, rather
than the requisite paths of the expressions themselves.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--exclude-exprs</option></term>
<listitem>
<para>
Excludes the paths of Nix expressions. This causes the
closure property to be lost, that is, the resulting set of
paths is not enough to ensure realisibility.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--include-successors</option></term>
<listitem>
<para>
Also include the requisites of successors (normal forms).
Only the requisites of <emphasis>known</emphasis>
successors are included, i.e., the normal forms of
derivation expressions that have never been normalised will
not be included.
</para>
<para>
Note that not just the successor of a derivation expression
will be included, but also the successors of all input
expressions of that derivation expression. I.e., all
normal forms of subterms involved in the normalisation of
the top-level term are included.
</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--expansion</option></term>
<listitem>
<para>
For each identifier in <replaceable>args</replaceable>, prints
all expansions of that identifier, that is, all paths whose
current content matches the identifier.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--graph</option></term>
<listitem>
<para>
Prints a graph of the closure of the expressions identified by
<replaceable>args</replaceable> in the format of the
<command>dot</command> tool of AT&amp;T's GraphViz package.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect2>
</refsect1>
</refentry>

3
doc/manual/troubleshooting.xml
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@ -35,8 +35,7 @@
</para>
<screen>
$ rm `db_archive -a -h
<replaceable>prefix</replaceable>/var/nix/db`</screen>
$ rm `db_archive -a -h <replaceable>prefix</replaceable>/var/nix/db`</screen>
</sect1>