I've been trying to troubleshoot the cause of this PostGIS recheck bug we have reported by two people so far. The last test was a nice simple repeatable one that triggered the issue:
https://trac.osgeo.org/postgis/ticket/3418 from what I have seen this only affects cases where we are doing a distance check between two points, which we actually don't need to enable recheck for anyway, but trying to disable that seems like just shoving the real problem under the covers. Where it errors is this line 272 in src/backend/executor/nodeIndexscan https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/exe cutor/nodeIndexscan.c;h=3143bd94ec4499fba94b41693538b785c4b32e6c;hb=HEAD#l27 2 /* 259 * Was the ORDER BY value returned by the index accurate? The 260 * recheck flag means that the index can return inaccurate values, 261 * but then again, the value returned for any particular tuple 262 * could also be exactly correct. Compare the value returned by 263 * the index with the recalculated value. (If the value returned 264 * by the index happened to be exact right, we can often avoid 265 * pushing the tuple to the queue, just to pop it back out again.) 266 */ 267 cmp = cmp_orderbyvals(node->iss_OrderByValues, 268 node->iss_OrderByNulls, 269 scandesc->xs_orderbyvals, 270 scandesc->xs_orderbynulls, 271 node); 272 if (cmp < 0) 273 elog(ERROR, "index returned tuples in wrong order"); 274 else if (cmp == 0) 275 was_exact = true; 276 else 277 was_exact = false; If things are out of order, why isn't just going to was_exact = false good enough? I'm not sure if the mistake is in our PostGIS code or something in PostgreSQL recheck logic. If I change the elog(ERROR ...) to a elog(NOTICE, the answers are correct and sort order is right. Under what conditions would cmp return less than 0? I tried following the code in cmp_orderbyvals, but got lost and trying to put elog notices in to see what the distance is returning (I probably did it wrong), just ended up crashing by backend. Thanks for any thoughts, Regina -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
