Change layer cache logic to target destination layers rather than sources.

In a future commit we'll fingerprint layers to detect changes.
Comparing modification times is not enough since some sources (for
instance Naturvårdsverket's SCI_Rikstackande) are updated on the server
even though no objects are being added; the source layer remains
unchanged but the file differs because of OBJECTID changes we are not
interested in.

Rather than using another cache layer/table for fingerprints, we cache
destination layernames rather than triplets (source_path, archive_member,
layername), along with the time at which the import was started rather
than source_path's mtime.

There is indeed no value in having exact source_path's mtime in the
cache.  What we need is simply a way to detect whether source paths have
been updated in a subsequent run.  Thanks to the shared locks the ctime
of any updated source path will be at least the time when the locks are
released, thereby exceeding the last_updated value.

1 files changed, 1 insertions, 1 deletions

diff --git a/config.yml b/config.yml
index 8fa6ca7..08ee039 100644
--- a/config.yml
+++ b/config.yml
@@ -108,7 +108,7 @@ dataset:
   open-options-publish:
     USER: webmap_guest
 
-  sourcecache-layername: public.sourcecache
+  layercache: public.layercache
 
   # Optional dictionary of default layer creation options, cf.
   # https://gdal.org/drivers/vector/pg.html#layer-creation-options or