update

Author: mutianf

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/readrows/LargeRowPaginationUtil.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.cloud.bigtable.data.v2.stub.readrows;
+
+import com.google.api.core.InternalApi;
+import com.google.cloud.bigtable.data.v2.models.Filters;
+
+/**
+ * A paginator for fetching extremely large rows from Bigtable chunk by chunk to avoid the 256MB gRPC size limit.
+ * It yields Filters that chunk the row by cell limits and handles limit halving if FAILED_PRECONDITION occurs.
+ */
+@InternalApi("For internal usage only")
+public class LargeRowPaginator {
+    private int currentLimit;
+    private int currentOffset;
+    private boolean hasMore;
+
+    public LargeRowPaginator(int initialLimit) {
+        this.currentLimit = initialLimit;
+        this.currentOffset = 0;
+        this.hasMore = true;
+    }
+
+    /**
+     * Yields the filter required to fetch the next chunk of cells for the large row.
+     */
+    public Filters.Filter getNextFilter() {
+        Filters.ChainFilter chain = Filters.FILTERS.chain();
+        if (currentOffset > 0) {
+            chain.filter(Filters.FILTERS.offset().cellsPerRow(currentOffset));
+        }
+        chain.filter(Filters.FILTERS.limit().cellsPerRow(currentLimit));
+        return chain;
+    }
+
+    /**
+     * Advances the internal offset. Call this after a successful Bigtable API call.
+     * @param cellsReadInLastChunk The number of cells returned in the last chunk.
+     * @return true if there are potentially more cells to fetch.
+     */
+    public boolean advance(int cellsReadInLastChunk) {
+        this.currentOffset += cellsReadInLastChunk;
+        
+        // If we read fewer cells than requested, we've hit the end of the row.
+        if (cellsReadInLastChunk < currentLimit) {
+            this.hasMore = false;
+        }
+        return this.hasMore;
+    }
+
+    /**
+     * Call this if the Bigtable API call fails with a FAILED_PRECONDITION due to size limits.
+     * It reduces the batch size to fetch a smaller chunk on the next attempt.
+     */
+    public void halveLimit() {
+        this.currentLimit /= 2;
+        if (this.currentLimit == 0) {
+            throw new RuntimeException("Cannot divide limit further. A single cell might be too large.");
+        }
+    }
+
+    public boolean hasNext() {
+        return this.hasMore;
+    }
+}