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authorJohn Firebaugh <john.firebaugh@gmail.com>2016-02-09 17:19:27 -0800
committerJohn Firebaugh <john.firebaugh@gmail.com>2016-02-10 15:40:20 -0800
commitdb3620c58f0c3351e26b0e3bcfd23ff414f829a1 (patch)
treee8def564e12307a997270b66a4ed46b68f5e13a4 /include/mbgl/util/constants.hpp
parent591012401072e63b89071787d90bf5ae4362dca1 (diff)
downloadqtlocation-mapboxgl-db3620c58f0c3351e26b0e3bcfd23ff414f829a1.tar.gz
[core] Implement an eviction policy for OfflineDatabase
When inserting an cached resource, or removing a region, remove least-recently used resources and tiles, not used by offline regions, until the used database size, as calculated by multiplying the number of in-use pages by the page size, is less than the maximum cache size minus 5 times the page size. In addition, OfflineDatabase may be configured to ignore cache puts of individual resources larger than a certain size. This policy is similar but not identical to the former SQLiteCache policy: * It accounts for offline, by exempting resources required by offline regions from eviction. * It must delete from two tables (resources and tiles), rather than one. Currently the strategy is naive: evict 50 rows at a time from each table. * It makes maximumCacheSize and maximumCacheEntrySize completely independent. The SQLiteCache implementation evicted when `usedSize > maximumCacheSize - 2 * maximumCacheEntrySize`. This evicts when `usedSize > maximumCacheSize - 5 * pageSize`. * It uses a non-unlimited default value for maximumCacheSize: 50 MB. We should have always had a limit in place; "a cache without an eviction policy is a resource leak".
Diffstat (limited to 'include/mbgl/util/constants.hpp')
-rw-r--r--include/mbgl/util/constants.hpp3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/mbgl/util/constants.hpp b/include/mbgl/util/constants.hpp
index 24f4b5ee72..667e2f8497 100644
--- a/include/mbgl/util/constants.hpp
+++ b/include/mbgl/util/constants.hpp
@@ -21,6 +21,9 @@ extern const double PITCH_MAX;
extern const double MIN_ZOOM;
extern const double MAX_ZOOM;
+extern const uint64_t DEFAULT_MAX_CACHE_SIZE;
+extern const uint64_t DEFAULT_MAX_CACHE_ENTRY_SIZE;
+
} // namespace util
namespace debug {