LMDB: add utilities that allow to explore LMDB contents - #363
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Intended for debugging and testing purposes
marisn
marked this pull request as ready for review
October 3, 2025 12:31
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What wasn't discussed if all functionality should be wrapped in a single utility or kept as two separate. Both are valid options. Yes, thinking is not my strong point. |
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I personally prefer 2 separate utilities, as you have done. |
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As LMDB stores a binary blob, there are no CLI tools to explore database contents. These two utilities allow to look inside a LMDB cache by listing all keys stored in it and extracting data by key value.
Usage examples
Find out how many tiles are stored in the database:
List all 1296 tile keys (be ware of printing keys for large databases!)
$ mapcache_lmdb_list -d o2016/ orto2016-L-{dim}-0-0-0.xxx orto2016-L-{dim}-0-0-1.xxx ...List all 1296 keys and additionally print tile timestamp and size. Size 4 indicates that it is a blank tile (just RGBA value).
$ mapcache_lmdb_list -d o2016/ -e orto2016-L-{dim}-0-2-1.xxx,2025-09-02T13:41:35Z,4 orto2016-L-{dim}-0-2-2.xxx,2025-09-02T13:41:35Z,1727 ...Extract one tile to a file
$ mapcache_lmdb_get -d o2016/ -k orto2016-L-{dim}-0-2-1.xxx -o my_tile.png Key found. Blank tile, color #ffffffff. Writing description to "my_tile.png" Timestamp: Tue, 02 Sep 2025 13:41:35 GMT $ mapcache_lmdb_get -d o2016/ -k orto2016-L-{dim}-0-2-2.xxx -o my_tile.png Key found. Writing 1727 image bytes to "my_tile.png" Timestamp: Tue, 02 Sep 2025 13:41:35 GMT