add bulk getTotalCount and mergeWith to PaginatedStore

Author: richardstartin

src/main/java/com/datadoghq/sketch/ddsketch/store/PaginatedStore.java

@@ -82,6 +82,22 @@ public int getMaxIndex() {
         throw new NoSuchElementException();
     }
 
+    @Override
+    public double getTotalCount() {
+        if (isEmpty()) {
+            return 0D;
+        }
+        double total = 0D;
+        for (double[] page : pages) {
+            if (null != page) {
+                for (double count : page) {
+                    total += count;
+                }
+            }
+        }
+        return total;
+    }
+
     @Override
     public void add(int index, double count) {
         if (count > 0) {
@@ -147,6 +163,84 @@ private void extendTo(int pageIndex) {
         this.pages = Arrays.copyOf(pages, pages.length + aligned(pageIndex - minPageIndex + 1));
     }
 
+    @Override
+    public void mergeWith(Store store) {
+        if (store.isEmpty()) {
+            return;
+        }
+        if (store instanceof PaginatedStore) {
+            mergeWith((PaginatedStore) store);
+        } else {
+            store.getStream().forEach(this::add);
+        }
+    }
+
+    private void mergeWith(PaginatedStore store) {
+        if (isEmpty()) {
+            this.pages = deepCopy(store.pages);
+            this.minPageIndex = store.minPageIndex;
+        } else {
+            int min = minPageIndex;
+            int max = minPageIndex + pages.length;
+            int storeMin = store.minPageIndex;
+            int storeMax = store.minPageIndex + store.pages.length;
+            if (max < storeMin) {
+                extendTo(storeMax);
+                for (int i = 0; i < store.pages.length; ++i) {
+                    double[] page = store.pages[i];
+                    if (null != page) {
+                        pages[i + storeMin - min] = Arrays.copyOf(page, page.length);
+                    }
+                }
+            } else if (min > storeMax) {
+                shiftPagesRight(storeMin);
+                for (int i = 0; i < store.pages.length; ++i) {
+                    double[] page = store.pages[i];
+                    if (null != page) {
+                        pages[i] = Arrays.copyOf(page, page.length);
+                    }
+                }
+            } else if (min < storeMin) {
+                if (storeMax > max) {
+                    extendTo(storeMax);
+                }
+                for (int i = 0; i < store.pages.length; ++i) {
+                    double[] page = store.pages[i];
+                    if (null != page) {
+                        double[] target = pages[i + storeMin - min];
+                        if (null == target) {
+                            pages[i + storeMin - min] = Arrays.copyOf(page, page.length);
+                        } else {
+                            for (int j = 0; j < page.length; ++j) {
+                                target[j] += page[j];
+                            }
+                        }
+                    }
+                }
+            } else {
+                if (min > storeMin) {
+                    shiftPagesRight(storeMin);
+                }
+                if (storeMax > max) {
+                    extendTo(storeMax);
+                }
+                for (int i = 0; i < store.pages.length; ++i) {
+                    double[] page = store.pages[i];
+                    if (null != page) {
+                        double[] target = pages[i];
+                        if (null == target) {
+                            pages[i] = Arrays.copyOf(page, page.length);
+                        } else {
+                            for (int j = 0; j < page.length; ++j) {
+                                target[j] += page[j];
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
     @Override
     public Store copy() {
         return new PaginatedStore(this);

src/test/java/com/datadoghq/sketch/ddsketch/store/PaginatedStoreTest.java

@@ -1,6 +1,5 @@
 package com.datadoghq.sketch.ddsketch.store;
 
-import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;

src/test/java/com/datadoghq/sketch/ddsketch/store/StoreTest.java

@@ -219,6 +219,9 @@ void testMergingFarApart() {
         testMerging(new int[]{ -10000 }, new int[]{ 10000 });
         testMerging(new int[]{ 10000 }, new int[]{ -10000 });
         testMerging(new int[]{ 10000 }, new int[]{ -10000 }, new int[]{ 0 });
+        testMerging(new int[]{ -10000, 10000 }, new int[]{ -5000, 5000 });
+        testMerging(new int[]{ -5000, 5000 }, new int[]{ -10000, 10000 });
+        testMerging(new int[]{ -5000, 10000 }, new int[]{ -10000, 5000 });
         testMerging(new int[]{ 10000, 0 }, new int[]{ -10000 }, new int[]{ 0 });
     }