From e99bb79e505f7af40376b7ee0ad8547b0e9ed370 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 24 Aug 2011 23:50:25 -0400 Subject: [PATCH] Fix pgstatindex() to give consistent results for empty indexes. For an empty index, the pgstatindex() function would compute 0.0/0.0 for its avg_leaf_density and leaf_fragmentation outputs. On machines that follow the IEEE float arithmetic standard with any care, that results in a NaN. However, per report from Rushabh Lathia, Microsoft couldn't manage to get this right, so you'd get a bizarre error on Windows. Fix by forcing the results to be NaN explicitly, rather than relying on the division operator to give that or the snprintf function to print it correctly. I have some doubts that this is really the most useful definition, but it seems better to remain backward-compatible with those platforms for which the behavior wasn't completely broken. Back-patch to 8.2, since the code is like that in all current releases. --- contrib/pgstattuple/pgstatindex.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/contrib/pgstattuple/pgstatindex.c b/contrib/pgstattuple/pgstatindex.c index 83b50bb432..9a7af67778 100644 --- a/contrib/pgstattuple/pgstatindex.c +++ b/contrib/pgstattuple/pgstatindex.c @@ -234,9 +234,17 @@ pgstatindex(PG_FUNCTION_ARGS) values[j] = palloc(32); snprintf(values[j++], 32, INT64_FORMAT, indexStat.deleted_pages); values[j] = palloc(32); - snprintf(values[j++], 32, "%.2f", 100.0 - (double) indexStat.free_space / (double) indexStat.max_avail * 100.0); + if (indexStat.max_avail > 0) + snprintf(values[j++], 32, "%.2f", + 100.0 - (double) indexStat.free_space / (double) indexStat.max_avail * 100.0); + else + snprintf(values[j++], 32, "NaN"); values[j] = palloc(32); - snprintf(values[j++], 32, "%.2f", (double) indexStat.fragments / (double) indexStat.leaf_pages * 100.0); + if (indexStat.leaf_pages > 0) + snprintf(values[j++], 32, "%.2f", + (double) indexStat.fragments / (double) indexStat.leaf_pages * 100.0); + else + snprintf(values[j++], 32, "NaN"); tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc), values);