Avoid writing the status database for read-only commands.

Resolves microsoft/vcpkg#10812

Depends on microsoft#1529
Extracted from  microsoft#1514

Splits database_load_check into database_load, which merely loads the current database, and database_load_collapse, which additionally smashes any outstanding update files.
Splits get_installed_files into get_installed_files and get_installed_files_and_upgrade. The former avoids the format conversion and thus does not need to write.

Reading commands database_load / get_installed_files:
* export
* list
* owns
* package_info
* update

Writing commands which use database_load_collapse / get_installed_files_and_upgrade. Also intend to call database_load_collapse at the end after successful completion so that the status file has all update records merged in where possible.
* build
* ci
* install
* remove
* set-installed
* upgrade

include/vcpkg/base/contractual-constants.h

@@ -344,6 +344,8 @@ namespace vcpkg
     inline constexpr StringLiteral FilePortfileDotCMake = "portfile.cmake";
     inline constexpr StringLiteral FileShare = "share";
     inline constexpr StringLiteral FileStatus = "status";
+    inline constexpr StringLiteral FileStatusNew = "status-new";
+    inline constexpr StringLiteral FileStatusOld = "status-old";
     inline constexpr StringLiteral FileTools = "tools";
     inline constexpr StringLiteral FileUpdates = "updates";
     inline constexpr StringLiteral FileUsage = "usage";

include/vcpkg/vcpkglib.h

@@ -13,8 +13,12 @@
 
 namespace vcpkg
 {
-    StatusParagraphs database_load_check(const Filesystem& fs, const InstalledPaths& installed);
+    // Read the status database
+    StatusParagraphs database_load(const ReadOnlyFilesystem& fs, const InstalledPaths& installed);
+    // Read the status database, and collapse update records into the current status file
+    StatusParagraphs database_load_collapse(const Filesystem& fs, const InstalledPaths& installed);
 
+    // Adds an update record
     void write_update(const Filesystem& fs, const InstalledPaths& installed, const StatusParagraph& p);
 
     struct StatusParagraphAndAssociatedFiles
@@ -24,9 +28,16 @@ namespace vcpkg
     };
 
     std::vector<InstalledPackageView> get_installed_ports(const StatusParagraphs& status_db);
-    std::vector<StatusParagraphAndAssociatedFiles> get_installed_files(const Filesystem& fs,
+
+    // Reads the installed files from the status database.
+    std::vector<StatusParagraphAndAssociatedFiles> get_installed_files(const ReadOnlyFilesystem& fs,
                                                                        const InstalledPaths& installed,
                                                                        const StatusParagraphs& status_db);
+    // Reads the installed files from the status database, converting installed file lists to the current version if
+    // necessary.
+    std::vector<StatusParagraphAndAssociatedFiles> get_installed_files_and_upgrade(const Filesystem& fs,
+                                                                                   const InstalledPaths& installed,
+                                                                                   const StatusParagraphs& status_db);
 
     std::string shorten_text(StringView desc, const size_t length);
 } // namespace vcpkg

src/vcpkg/commands.build.cpp

@@ -132,7 +132,7 @@ namespace vcpkg
         auto& var_provider = *var_provider_storage;
         var_provider.load_dep_info_vars({{spec}}, host_triplet);
 
-        StatusParagraphs status_db = database_load_check(paths.get_filesystem(), paths.installed());
+        StatusParagraphs status_db = database_load_collapse(paths.get_filesystem(), paths.installed());
         auto action_plan = create_feature_install_plan(
             provider,
             var_provider,

src/vcpkg/commands.ci.cpp

@@ -502,7 +502,7 @@ namespace vcpkg
         }
         else
         {
-            StatusParagraphs status_db = database_load_check(paths.get_filesystem(), paths.installed());
+            StatusParagraphs status_db = database_load_collapse(paths.get_filesystem(), paths.installed());
             auto already_installed = adjust_action_plan_to_status_db(action_plan, status_db);
             Util::erase_if(already_installed,
                            [&](auto& spec) { return Util::Sets::contains(split_specs->known, spec); });

src/vcpkg/commands.export.cpp

@@ -596,7 +596,7 @@ namespace vcpkg
                                  Triplet host_triplet)
     {
         (void)host_triplet;
-        const StatusParagraphs status_db = database_load_check(paths.get_filesystem(), paths.installed());
+        const StatusParagraphs status_db = database_load(paths.get_filesystem(), paths.installed());
         const auto opts = handle_export_command_arguments(paths, args, default_triplet, status_db);
 
         // Load ports from ports dirs

src/vcpkg/commands.install.cpp

@@ -224,7 +224,7 @@ namespace vcpkg
         const auto package_dir = paths.package_dir(bcf.core_paragraph.spec);
         Triplet triplet = bcf.core_paragraph.spec.triplet();
         const std::vector<StatusParagraphAndAssociatedFiles> pgh_and_files =
-            get_installed_files(fs, installed, *status_db);
+            get_installed_files_and_upgrade(fs, installed, *status_db);
 
         const SortedVector<std::string> package_files = build_list_of_package_files(fs, package_dir);
         const SortedVector<file_pack> installed_files = build_list_of_installed_files(pgh_and_files, triplet);
@@ -619,6 +619,7 @@ namespace vcpkg
             this_install.current_summary.build_result.emplace(std::move(result));
         }
 
+        database_load_collapse(fs, paths.installed());
         msg::println(msgTotalInstallTime, msg::elapsed = timer.to_string());
         return InstallSummary{std::move(results)};
     }
@@ -1288,7 +1289,7 @@ namespace vcpkg
 
         // create the plan
         msg::println(msgComputingInstallPlan);
-        StatusParagraphs status_db = database_load_check(fs, paths.installed());
+        StatusParagraphs status_db = database_load_collapse(fs, paths.installed());
 
         // Note: action_plan will hold raw pointers to SourceControlFileLocations from this map
         auto action_plan = create_feature_install_plan(provider, var_provider, specs, status_db, create_options);

src/vcpkg/commands.list.cpp

@@ -1,4 +1,5 @@
 #include <vcpkg/base/contractual-constants.h>
+#include <vcpkg/base/files.h>
 #include <vcpkg/base/strings.h>
 #include <vcpkg/base/util.h>
 
@@ -103,7 +104,7 @@ namespace vcpkg
         msg::default_output_stream = OutputStream::StdErr;
         const ParsedArguments options = args.parse_arguments(CommandListMetadata);
 
-        const StatusParagraphs status_paragraphs = database_load_check(paths.get_filesystem(), paths.installed());
+        const StatusParagraphs status_paragraphs = database_load(paths.get_filesystem(), paths.installed());
         auto installed_ipv = get_installed_ports(status_paragraphs);
 
         const auto output_json = Util::Sets::contains(options.switches, SwitchXJson);

src/vcpkg/commands.owns.cpp

@@ -1,3 +1,5 @@
+#include <vcpkg/base/files.h>
+
 #include <vcpkg/commands.owns.h>
 #include <vcpkg/statusparagraphs.h>
 #include <vcpkg/vcpkgcmdarguments.h>
@@ -8,7 +10,7 @@ using namespace vcpkg;
 
 namespace
 {
-    void search_file(const Filesystem& fs,
+    void search_file(const ReadOnlyFilesystem& fs,
                      const InstalledPaths& installed,
                      const std::string& file_substr,
                      const StatusParagraphs& status_db)
@@ -46,7 +48,7 @@ namespace vcpkg
     void command_owns_and_exit(const VcpkgCmdArguments& args, const VcpkgPaths& paths)
     {
         const auto parsed = args.parse_arguments(CommandOwnsMetadata);
-        const StatusParagraphs status_db = database_load_check(paths.get_filesystem(), paths.installed());
+        const StatusParagraphs status_db = database_load(paths.get_filesystem(), paths.installed());
         search_file(paths.get_filesystem(), paths.installed(), parsed.command_arguments[0], status_db);
         Checks::exit_success(VCPKG_LINE_INFO);
     }

src/vcpkg/commands.package-info.cpp

@@ -61,7 +61,7 @@ namespace vcpkg
         auto& fs = paths.get_filesystem();
         if (installed)
         {
-            const StatusParagraphs status_paragraphs = database_load_check(fs, paths.installed());
+            const StatusParagraphs status_paragraphs = database_load(fs, paths.installed());
             std::set<PackageSpec> specs_written;
             std::vector<PackageSpec> specs_to_write;
             for (auto&& arg : options.command_arguments)

src/vcpkg/commands.remove.cpp

@@ -150,7 +150,7 @@ namespace
 
     std::vector<std::string> valid_arguments(const VcpkgPaths& paths)
     {
-        const StatusParagraphs status_db = database_load_check(paths.get_filesystem(), paths.installed());
+        const StatusParagraphs status_db = database_load(paths.get_filesystem(), paths.installed());
         auto installed_packages = get_installed_ports(status_db);
 
         return Util::fmap(installed_packages, [](auto&& pgh) -> std::string { return pgh.spec().to_string(); });
@@ -183,7 +183,7 @@ namespace vcpkg
         }
         const ParsedArguments options = args.parse_arguments(CommandRemoveMetadata);
 
-        StatusParagraphs status_db = database_load_check(paths.get_filesystem(), paths.installed());
+        StatusParagraphs status_db = database_load_collapse(paths.get_filesystem(), paths.installed());
         std::vector<PackageSpec> specs;
         if (Util::Sets::contains(options.switches, SwitchOutdated))
         {
@@ -301,6 +301,7 @@ namespace vcpkg
             }
         }
 
+        database_load_collapse(fs, paths.installed());
         Checks::exit_success(VCPKG_LINE_INFO);
     }
 }

src/vcpkg/commands.set-installed.cpp

@@ -211,7 +211,7 @@ namespace vcpkg
         }
 
         // currently (or once) installed specifications
-        auto status_db = database_load_check(fs, paths.installed());
+        auto status_db = database_load_collapse(fs, paths.installed());
         adjust_action_plan_to_status_db(action_plan, status_db);
 
         print_plan(action_plan, paths.builtin_ports_directory());

src/vcpkg/commands.update.cpp

@@ -65,7 +65,7 @@ namespace vcpkg
         msg::println(msgLocalPortfileVersion);
 
         auto& fs = paths.get_filesystem();
-        const StatusParagraphs status_db = database_load_check(fs, paths.installed());
+        const StatusParagraphs status_db = database_load(fs, paths.installed());
 
         auto registry_set = paths.make_registry_set();
         PathsPortFileProvider provider(*registry_set,

src/vcpkg/commands.upgrade.cpp

@@ -76,7 +76,7 @@ namespace vcpkg
         const CreateUpgradePlanOptions create_upgrade_plan_options{
             nullptr, host_triplet, paths.packages(), unsupported_port_action};
 
-        StatusParagraphs status_db = database_load_check(paths.get_filesystem(), paths.installed());
+        StatusParagraphs status_db = database_load_collapse(paths.get_filesystem(), paths.installed());
 
         // Load ports from ports dirs
         auto& fs = paths.get_filesystem();