sqlite> explain query plan select max(utc_time) from RequestLog;
0|0|0|SEARCH TABLE RequestLog USING COVERING INDEX key (~1 rows) # very fast

sqlite> explain query plan select min(utc_time) from RequestLog;
0|0|0|SEARCH TABLE RequestLog USING COVERING INDEX key (~1 rows) # very fast

sqlite> explain query plan select min(utc_time), max(utc_time) from RequestLog;
0|0|0|SCAN TABLE RequestLog (~8768261 rows) # will be very very slow

当我分别使用min和时max，它可以完美地工作。但是，出于某些原因，当我同时选择min和时，sqlite将“忘记”索引max。有什么我可以做的配置（我Analyze已经用过了，将无法使用）？或对此行为有任何解释吗？

编辑1

sqlite> .schema

CREATE TABLE FixLog(
                    app_id text,  __key__id INTEGER,
                    secret text, trace_code text, url text,
                    action text,facebook_id text,ip text,
                    tw_time datetime,time datetime,
                    tag text,to_url text,
                    from_url text,referer text,weight integer,
                    Unique(app_id, __key__id)
                    );
CREATE INDEX key4 on FixLog(action);
CREATE INDEX time on FixLog(time desc);
CREATE INDEX tw_time on FixLog(tw_time desc);



sqlite> explain query select min(time) from FixLog;
0|0|0|SEARCH TABLE FixLog USING COVERING INDEX time (~1 rows)
sqlite> explain query select max(time) from FixLog;
0|0|0|SEARCH TABLE FixLog USING COVERING INDEX time (~1 rows)
sqlite> explain query plan select max(time), min(time) from FixLog;
0|0|0|SCAN TABLE FixLog (~1000000 rows)