more fine grained dependency tracking #813

with the initial implementation of DbSchemaResultCacheMetaExtension phpstan-dba learned to invalidate the whole phpstan result cache when the external schema changes.

this means all code, no matter whether it depends on the database schema has to be re-analyzed.

with #810 phpstan-dba learned to re-analyse only such code which depends on the database schema. that way not all code needed to be re-analyzed.

for the future we could improve this even more:

Step 1: track which database tables are referenced from which code. build a schema-hash per database table instead of per the whole schema. re-analyze only code relevant to the tables which was changed

Step 2 (even more fine grained) : track which table-columns are referenced from which code. when columns change in the db-schema re-analyze only the code which depends on the changed column(s). this needs to be aware of implicit references like SELECT * etc.