forked from lix-project/lix
![Eelco Dolstra](/assets/img/avatar_default.png)
* Open all database tables (Db objects) at initialisation time, not every time they are used. This is necessary because tables have to outlive all transactions that refer to them.
80 lines
1.8 KiB
C++
80 lines
1.8 KiB
C++
#ifndef __GLOBALS_H
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#define __GLOBALS_H
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#include <string>
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#include "db.hh"
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using namespace std;
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extern Database nixDB;
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/* Database tables. */
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/* dbPath2Id :: Path -> FSId
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Each pair (p, id) records that path $p$ contains an expansion of
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$id$. */
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extern TableId dbPath2Id;
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/* dbId2Paths :: FSId -> [Path]
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A mapping from ids to lists of paths. */
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extern TableId dbId2Paths;
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/* dbSuccessors :: FSId -> FSId
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Each pair $(id_1, id_2)$ in this mapping records the fact that a
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successor of an fstate expression stored in a file with identifier
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$id_1$ is stored in a file with identifier $id_2$.
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Note that a term $y$ is successor of $x$ iff there exists a
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sequence of rewrite steps that rewrites $x$ into $y$.
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*/
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extern TableId dbSuccessors;
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/* dbSubstitutes :: FSId -> [FSId]
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Each pair $(id, [ids])$ tells Nix that it can realise any of the
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fstate expressions referenced by the identifiers in $ids$ to
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generate a path with identifier $id$.
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The main purpose of this is for distributed caching of derivates.
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One system can compute a derivate with hash $h$ and put it on a
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website (as a Nix archive), for instance, and then another system
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can register a substitute for that derivate. The substitute in
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this case might be an fstate expression that fetches the Nix
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archive.
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*/
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extern TableId dbSubstitutes;
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/* Path names. */
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/* nixStore is the directory where we generally store atomic and
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derived files. */
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extern string nixStore;
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extern string nixDataDir; /* !!! fix */
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/* nixLogDir is the directory where we log various operations. */
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extern string nixLogDir;
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/* nixDBPath is the path name of our Berkeley DB environment. */
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extern string nixDBPath;
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/* Open the database environment. */
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void openDB();
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/* Create the required database tables. */
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void initDB();
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#endif /* !__GLOBALS_H */
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