SQLite does not have "query caching". It does have a "page cache" that will keep heavily used pages iin memory. There is also the possibility of a file-system/os-level cache. To break down the 1.6 seconds required for the first query, try executing an sql script. In linux this would be along the lines of:
> date; sqlite3 file.db < script.sql;date With script.sql containing: Select strftime('%Y-%m-%d %H:%M:%S.%f'); Select strftime('%Y-%m-%d %H:%M:%S.%f'); .describe adas_link_geometry Select strftime('%Y-%m-%d %H:%M:%S.%f'); .describe idx_adas_link_geometry Select strftime('%Y-%m-%d %H:%M:%S.%f'); Select <your statement>; Select strftime('%Y-%m-%d %H:%M:%S.%f'); Select <your statement>; Select strftime('%Y-%m-%d %H:%M:%S.%f'); Select <your statement>; Select strftime('%Y-%m-%d %H:%M:%S.%f'); This should give you an idea of where the time is being spent. -----Ursprüngliche Nachricht----- Von: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] Im Auftrag von David Ashman - Zone 7 Engineering, LLC Gesendet: Dienstag, 20. März 2018 16:34 An: sqlite-users@mailinglists.sqlite.org Betreff: [EXTERNAL] [sqlite] R*Trees query data cached? Hello - I have a question on SQLite query data buffering. I'm successfully using SQLite v3.22.0 on an embedded ARM processor from ST with SD card. The database file size is about 750MB. The file system is Segger emFile FAT32. I've configured SQLite to use 6MB RAM for heap. I've done some query time benchmarking and found that the very first R*Trees query takes about 1.6 seconds to complete. Each successive R*Trees query (same query string with slightly different search parameters) takes about 11ms to complete. Being new to SQLite and spatial queries, I'm trying to understand the substantial query time differences... does SQLite cache data from each query for future queries? The initial query:SELECT LINK_ID, FROM_REF_ELEVATION, TO_REF_ELEVATION FROM adas_link_geometry, idx_adas_link_geometry WHERE adas_link_geometry.ROWID = idx_adas_link_geometry.id AND minLat > 454760320 AND maxLat < 454800320 AND minLong > -1226807072 AND maxLong < -1226767072; Thanks in advance,Dave _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users ___________________________________________ Gunter Hick | Software Engineer | Scientific Games International GmbH | Klitschgasse 2-4, A-1130 Vienna | FN 157284 a, HG Wien, DVR: 0430013 | (O) +43 1 80100 - 0 May be privileged. May be confidential. Please delete if not the addressee. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users