diff options
Diffstat (limited to 'src/backend/nodes/tidbitmap.c')
| -rw-r--r-- | src/backend/nodes/tidbitmap.c | 37 |
1 files changed, 25 insertions, 12 deletions
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c index c47d5849ef7..acfe6b263c6 100644 --- a/src/backend/nodes/tidbitmap.c +++ b/src/backend/nodes/tidbitmap.c @@ -265,7 +265,6 @@ TIDBitmap * tbm_create(long maxbytes, dsa_area *dsa) { TIDBitmap *tbm; - long nbuckets; /* Create the TIDBitmap struct and zero all its fields */ tbm = makeNode(TIDBitmap); @@ -273,17 +272,7 @@ tbm_create(long maxbytes, dsa_area *dsa) tbm->mcxt = CurrentMemoryContext; tbm->status = TBM_EMPTY; - /* - * Estimate number of hashtable entries we can have within maxbytes. This - * estimates the hash cost as sizeof(PagetableEntry), which is good enough - * for our purpose. Also count an extra Pointer per entry for the arrays - * created during iteration readout. - */ - nbuckets = maxbytes / - (sizeof(PagetableEntry) + sizeof(Pointer) + sizeof(Pointer)); - nbuckets = Min(nbuckets, INT_MAX - 1); /* safety limit */ - nbuckets = Max(nbuckets, 16); /* sanity limit */ - tbm->maxentries = (int) nbuckets; + tbm->maxentries = (int) tbm_calculate_entries(maxbytes); tbm->lossify_start = 0; tbm->dsa = dsa; tbm->dsapagetable = InvalidDsaPointer; @@ -1546,3 +1535,27 @@ pagetable_free(pagetable_hash *pagetable, void *pointer) tbm->dsapagetableold = InvalidDsaPointer; } } + +/* + * tbm_calculate_entries + * + * Estimate number of hashtable entries we can have within maxbytes. + */ +long +tbm_calculate_entries(double maxbytes) +{ + long nbuckets; + + /* + * Estimate number of hashtable entries we can have within maxbytes. This + * estimates the hash cost as sizeof(PagetableEntry), which is good enough + * for our purpose. Also count an extra Pointer per entry for the arrays + * created during iteration readout. + */ + nbuckets = maxbytes / + (sizeof(PagetableEntry) + sizeof(Pointer) + sizeof(Pointer)); + nbuckets = Min(nbuckets, INT_MAX - 1); /* safety limit */ + nbuckets = Max(nbuckets, 16); /* sanity limit */ + + return nbuckets; +} |