addition 3 centriods and check overflow

src/query/inc/tdigest.h

@@ -27,7 +27,7 @@
 #endif
 
 #define COMPRESSION 400
-#define GET_CENTROID(compression)  (ceil(compression * M_PI / 2) + 1)
+#define GET_CENTROID(compression)  (ceil(compression * M_PI / 2) + 1 + 3) // addition 3 centroid
 #define GET_THRESHOLD(compression) (7.5 + 0.37 * compression - 2e-4 * pow(compression, 2))
 #define TDIGEST_SIZE(compression)  (sizeof(TDigest) + sizeof(SCentroid)*GET_CENTROID(compression) + sizeof(SPt)*GET_THRESHOLD(compression))
 

src/query/src/tdigest.c

@@ -78,7 +78,9 @@ static void mergeCentroid(SMergeArgs *args, SCentroid *merge) {
             args->weight_so_far / args->t->total_weight);
 
     if (k2 - args->k1 > 1 && c->weight > 0) {
+        if(args->idx + 1 < args->t->size) { // check avoid overflow
             args->idx++; 
+        }
         args->k1 = INTEGRATED_LOCATION(args->t->compression,
                 (args->weight_so_far - merge->weight) / args->t->total_weight);
     }