diff options
Diffstat (limited to 'src/backend/access/gist/gistbuild.c')
| -rw-r--r-- | src/backend/access/gist/gistbuild.c | 32 |
1 files changed, 23 insertions, 9 deletions
diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c index 988896d289f..eb39c667c15 100644 --- a/src/backend/access/gist/gistbuild.c +++ b/src/backend/access/gist/gistbuild.c @@ -323,8 +323,8 @@ gistInitBuffering(GISTBuildState *buildstate) * calculating levelStep is very close to Arge et al's formula. For a * large B, our formula gives a value that is 2x higher. * - * The average size of a subtree of depth n can be calculated as a - * geometric series: + * The average size (in pages) of a subtree of depth n can be calculated + * as a geometric series: * * B^0 + B^1 + B^2 + ... + B^n = (1 - B^(n + 1)) / (1 - B) * @@ -353,14 +353,28 @@ gistInitBuffering(GISTBuildState *buildstate) * the hash table. */ levelStep = 1; - while ( - /* subtree must fit in cache (with safety factor of 4) */ - (1 - pow(avgIndexTuplesPerPage, (double) (levelStep + 1))) / (1 - avgIndexTuplesPerPage) < effective_cache_size / 4 - && - /* each node in the lowest level of a subtree has one page in memory */ - (pow(maxIndexTuplesPerPage, (double) levelStep) < (maintenance_work_mem * 1024) / BLCKSZ) - ) + for (;;) { + double subtreesize; + double maxlowestlevelpages; + + /* size of an average subtree at this levelStep (in pages). */ + subtreesize = + (1 - pow(avgIndexTuplesPerPage, (double) (levelStep + 1))) / + (1 - avgIndexTuplesPerPage); + + /* max number of pages at the lowest level of a subtree */ + maxlowestlevelpages = pow(maxIndexTuplesPerPage, (double) levelStep); + + /* subtree must fit in cache (with safety factor of 4) */ + if (subtreesize > effective_cache_size / 4) + break; + + /* each node in the lowest level of a subtree has one page in memory */ + if (maxlowestlevelpages > ((double) maintenance_work_mem * 1024) / BLCKSZ) + break; + + /* Good, we can handle this levelStep. See if we can go one higher. */ levelStep++; } |