[killertux]

Summary

• Schema tree refresh (all drivers). The tree cached each level on first expand and never fetched it again. If you expanded a schema while it was empty, then ran CREATE TABLE, the new table never appeared. The empty level also couldn't be expanded again, because descend_or_toggle does nothing when there are no children. A DDL statement only reloaded the autocomplete cache. Reported against Stoolap, but SQLite, Postgres and MySQL behave the same.
  • After DDL, every loaded level still in the tree is introspected again (SchemaPanel::refresh_targets). The cost is bounded by what the user has expanded.
  • populate() now merges into the existing children. Surviving tables keep their node, with their expanded columns/indices subtree, and refreshing a collapsed node doesn't open it.
  • Expanding a level that loaded empty fetches it again, which also picks up tables created by another process.
  • If the selected table is dropped, the selection moves to its parent.
• Bump to 0.19.1 (patch).

Test plan

• cargo fmt && cargo clippy --all-targets -- -D warnings && cargo test: 678 tests pass locally. There are 4 new SchemaPanel tests: a table created after an empty load, re-expanding an empty node, subtree and collapse state kept on refresh, and the selection moving to the parent when the selected table is dropped.
• Manual (tmux, throwaway HOME): expanded an empty stoolap::memory: schema, then ran CREATE TABLE test, CREATE TABLE other and DROP TABLE other. The tree updated after each statement without re-expanding.
• Manual: same flow on sqlite: and Postgres
• Manual: ALTER TABLE … ADD COLUMN with the table's columns expanded. The new column should appear.