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https://github.com/NixOS/nix.git
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188ed75d54
Hook into the evaluation to cache to cache the evaluation of flake members (stuff like `(builtins.getCache foo).bar.baz`). Also replaces the old eval cache that was used at the cli level.
148 lines
3 KiB
C++
148 lines
3 KiB
C++
/**
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* caching for a tree-like data structure (like Nix values)
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*
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* The cache is an sqlite db whose rows are the nodes of the tree, with a
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* pointer to their parent (except for the root of course)
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*/
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#pragma once
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#include "sync.hh"
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#include "hash.hh"
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#include "symbol-table.hh"
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#include <functional>
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#include <variant>
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namespace nix::tree_cache {
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struct AttrDb;
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class Cursor;
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class Cache : public std::enable_shared_from_this<Cache>
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{
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private:
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friend class Cursor;
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/**
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* The database holding the cache
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*/
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std::shared_ptr<AttrDb> db;
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SymbolTable & symbols;
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/**
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* Distinguished symbol indicating the root of the tree
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*/
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const Symbol rootSymbol;
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public:
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Cache(
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const Hash & useCache,
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SymbolTable & symbols
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);
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static std::shared_ptr<Cache> tryCreate(const Hash & useCache, SymbolTable & symbols);
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Cursor * getRoot();
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/**
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* Flush the cache to disk
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*/
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void commit();
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};
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enum AttrType {
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Unknown = 0,
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Attrs = 1,
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String = 2,
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Bool = 3,
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Int = 4,
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Double = 5,
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Thunk = 6,
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Missing = 7, // Missing fields of attribute sets
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Failed = 8,
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};
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struct attributeSet_t {};
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struct unknown_t {};
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struct thunk_t {};
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struct failed_t { string error; };
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struct missing_t { Symbol attrName; };
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typedef uint64_t AttrId;
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typedef std::pair<AttrId, Symbol> AttrKey;
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typedef std::pair<std::string, std::vector<std::pair<Path, std::string>>> string_t;
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typedef std::variant<
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attributeSet_t,
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string_t,
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unknown_t,
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thunk_t,
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missing_t,
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failed_t,
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bool,
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int64_t,
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double
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> AttrValue;
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struct RawValue {
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AttrType type;
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std::optional<std::string> value;
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std::vector<std::pair<Path, std::string>> context;
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std::string serializeContext() const;
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static const RawValue fromVariant(const AttrValue&);
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AttrValue toVariant() const;
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};
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/**
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* View inside the cache.
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*
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* A `Cursor` represents a node in the cached tree (be it a leaf or not)
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*/
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class Cursor : public std::enable_shared_from_this<Cursor>
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{
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/**
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* The overall cache of which this cursor is a view
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*/
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ref<Cache> root;
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typedef std::optional<std::pair<Cursor&, Symbol>> Parent;
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std::optional<AttrId> parentId;
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Symbol label;
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std::pair<AttrId, AttrValue> cachedValue;
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/**
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* Get the identifier for this node in the database
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*/
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AttrKey getKey();
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public:
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using Ref = Cursor*;
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// Create a new cache entry
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Cursor(ref<Cache> root, const Parent & parent, const AttrValue&);
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// Build a cursor from an existing cache entry
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Cursor(ref<Cache> root, const Parent & parent, const AttrId& id, const AttrValue&);
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AttrValue getCachedValue();
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void setValue(const AttrValue & v);
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Ref addChild(const Symbol & attrPath, const AttrValue & v);
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Ref findAlongAttrPath(const std::vector<Symbol> & attrPath);
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Ref maybeGetAttr(const Symbol & attrPath);
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std::vector<std::string> getChildren();
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std::optional<std::vector<std::string>> getChildrenAtPath(const std::vector<Symbol> & attrPath);
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};
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}
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