Merge pull request #1165 from go-kivik/sqlite55

Find/Explain support and other improvements to sqlite driver

Author: flimzy

x/sqlite/TODO.md

@@ -1,28 +1,28 @@
 # SQLite Driver TODO
 
-## Missing Implementations
-
-- [ ] **Explain** (`db.go`) — Currently returns "not implemented"; useful for
-  Mango query debugging.
-- [ ] **Missing options**:
-  - `att_encoding_info` (Get/Changes/Views)
-  - `batch` (Put)
-  - `heartbeat` (Changes)
-  - `execution_stats` (Find)
-
 ## Low Priority (polyfilled by kivik)
 
 - [ ] **BulkDocs** (`db.go`) — kivik emulates via individual Put/CreateDoc.
 - [ ] **Copy** (`db.go`) — kivik emulates via Get+Put.
 
 ## Performance / Code Quality
 
+- [ ] **Find cross-type comparison correctness** (`find.go`) —
+  `selectorToSQL` translates comparison operators (`$lt`, `$lte`, `$gt`,
+  `$gte`, `$eq`) to SQL, but SQLite doesn't support CouchDB's cross-type
+  ordering (null < bool < number < string < array < object). When
+  `selectorComplete=true`, the in-memory filter is skipped, producing
+  incorrect results for cross-type queries.
+- [ ] **`use_index` doesn't influence query execution** (`find.go`) — The hint
+  is validated and triggers a warning if missing, but doesn't guide the
+  query plan.
 - [ ] **Reduce caching** (`README.md`) — Reduce functions run on-demand with no
   intermediate result caching.
-- [ ] **Mango SQL optimization** (`find.go`) — These selectors work via
-  in-memory fallback but aren't translated to SQL: `$not`, `$nor`, `$nin`,
-  `$regex`, `$mod`, `$all`, `$elemMatch`, `$type`, `$size`, `$allMatch`,
-  `$keyMapMatch`.
+- [ ] **Mango SQL optimization** (`find.go`) — These selectors could be
+  translated to SQL for index support but aren't yet: `$size`, `$type`.
+  The remaining operators (`$nin`, `$mod`, `$all`, `$elemMatch`,
+  `$allMatch`, `$keyMapMatch`) aren't indexable in SQLite and are handled
+  adequately by the in-memory fallback.
 - [ ] **Filter in Go instead of SQL** (`query.go:569`) — Local and design
   document filtering during view updates is done in Go after fetching rows,
   rather than in the SQL query.

x/sqlite/createindex_test.go

@@ -43,6 +43,12 @@ func TestCreateIndex(t *testing.T) {
 		name:  "my-index",
 		index: json.RawMessage(`{"fields":["name"]}`),
 	})
+	tests.Add("mixed sort directions", test{
+		ddoc:    "_design/mixed",
+		name:    "mixed",
+		index:   json.RawMessage(`{"fields":[{"name":"asc"},{"age":"desc"}]}`),
+		wantErr: "Sorts currently only support a single direction for all fields",
+	})
 	tests.Add("creates a real SQLite index", func(t *testing.T) any {
 		db := newDB(t)
 		return test{

x/sqlite/db.go

@@ -116,10 +116,6 @@ func (db) Copy(context.Context, string, string, driver.Options) (string, error)
 	return "", errors.New("not implemented")
 }
 
-func (db) Explain(context.Context, any, driver.Options) (*driver.QueryPlan, error) {
-	return nil, errors.New("not implemented")
-}
-
 // errDatabaseNotFound converts a sqlite "no such table"  error into a kivik
 // database not found error
 func (d *db) errDatabaseNotFound(err error) error {