HBASE-29974: Persist filter hints across scan circuit breaks

hbase-client/src/main/java/org/apache/hadoop/hbase/filter/Filter.java

@@ -30,6 +30,10 @@
  * <li>{@link #reset()} : reset the filter state before filtering a new row.</li>
  * <li>{@link #filterAllRemaining()}: true means row scan is over; false means keep going.</li>
  * <li>{@link #filterRowKey(Cell)}: true means drop this row; false means include.</li>
+ * <li>{@link #getHintForRejectedRow(Cell)}: if {@code filterRowKey} returned true, optionally
+ * provide a seek hint to skip past the rejected row efficiently.</li>
+ * <li>{@link #getSkipHint(Cell)}: when a cell is structurally skipped (time-range, column, or
+ * version gate) before {@code filterCell} is reached, optionally provide a seek hint.</li>
  * <li>{@link #filterCell(Cell)}: decides whether to include or exclude this Cell. See
  * {@link ReturnCode}.</li>
  * <li>{@link #transformCell(Cell)}: if the Cell is included, let the filter transform the Cell.
@@ -188,6 +192,85 @@ public enum ReturnCode {
    */
   abstract public Cell getNextCellHint(final Cell currentCell) throws IOException;
 
+  /**
+   * Provides a seek hint to bypass row-by-row scanning after {@link #filterRowKey(Cell)} rejects a
+   * row. When {@code filterRowKey} returns {@code true} the scan pipeline would normally iterate
+   * through every remaining cell in the rejected row one-by-one (via {@code nextRow()}) before
+   * moving on. If the filter can determine a better forward position — for example, the next range
+   * boundary in a {@code MultiRowRangeFilter} — it should return that target cell here, allowing
+   * the scanner to seek directly past the unwanted rows.
+   * <p>
+   * Contract:
+   * <ul>
+   * <li>Only called after {@link #filterRowKey(Cell)} has returned {@code true} for the same
+   * {@code firstRowCell}.</li>
+   * <li>Implementations may use state that was set during {@link #filterRowKey(Cell)} (e.g. an
+   * updated range pointer), but <strong>must not</strong> invoke {@link #filterCell(Cell)} logic —
+   * the caller guarantees that {@code filterCell} has not been called for this row.</li>
+   * <li>The returned {@link Cell}, if non-null, must be an
+   * {@link org.apache.hadoop.hbase.ExtendedCell} because filters are evaluated on the server
+   * side.</li>
+   * <li>Returning {@code null} (the default) falls through to the existing {@code nextRow()}
+   * behaviour, preserving full backward compatibility.</li>
+   * <li>For reversed scans ({@link org.apache.hadoop.hbase.client.Scan#isReversed()}), the hint
+   * must point to a <em>smaller</em> row key (earlier in reverse-scan direction). The scanner
+   * validates hint direction and falls back to {@code nextRow()} if the hint does not advance in
+   * the scan direction.</li>
+   * <li><strong>Composite filter limitation:</strong> {@code FilterList}, {@code SkipFilter}, and
+   * {@code WhileMatchFilter} do not currently delegate this method to wrapped sub-filters. Hints
+   * from filters used inside these wrappers will be silently ignored.</li>
+   * </ul>
+   * @param firstRowCell the first cell encountered in the rejected row; contains the row key that
+   *                     was passed to {@code filterRowKey}
+   * @return a {@link Cell} representing the earliest position the scanner should seek to, or
+   *         {@code null} if this filter cannot provide a better position than a sequential skip
+   * @throws IOException in case an I/O or filter-specific failure needs to be signaled
+   * @see #filterRowKey(Cell)
+   */
+  public Cell getHintForRejectedRow(final Cell firstRowCell) throws IOException {
+    return null;
+  }
+
+  /**
+   * Provides a seek hint for cells that are structurally skipped by the scan pipeline
+   * <em>before</em> {@link #filterCell(Cell)} is ever reached. The pipeline short-circuits on
+   * several criteria — time-range mismatch, column-set exclusion, and version-limit exhaustion —
+   * and in each case the filter is bypassed entirely. When an implementation can compute a
+   * meaningful forward position purely from the cell's coordinates (without needing the
+   * {@code filterCell} call sequence), it should return that position here so the scanner can seek
+   * ahead instead of advancing one cell at a time.
+   * <p>
+   * Contract:
+   * <ul>
+   * <li>May be called for cells that have <strong>never</strong> been passed to
+   * {@link #filterCell(Cell)}.</li>
+   * <li>Implementations <strong>must not</strong> modify any filter state; this method is treated
+   * as logically stateless. Only filters whose hint computation is based solely on immutable
+   * configuration (e.g. a fixed column range or a fuzzy-row pattern) should override this.</li>
+   * <li>The returned {@link Cell}, if non-null, must be an
+   * {@link org.apache.hadoop.hbase.ExtendedCell} because filters are evaluated on the server
+   * side.</li>
+   * <li>Returning {@code null} (the default) falls through to the existing structural skip/seek
+   * behaviour, preserving full backward compatibility.</li>
+   * <li>For reversed scans, the returned cell must have a <em>smaller</em> row key (i.e., earlier
+   * in reverse-scan direction) than the {@code skippedCell}. Hints that do not advance in the scan
+   * direction are silently ignored.</li>
+   * <li><strong>Composite filter limitation:</strong> {@code FilterList}, {@code SkipFilter}, and
+   * {@code WhileMatchFilter} do not currently delegate this method to wrapped sub-filters. Hints
+   * from filters used inside these wrappers will be silently ignored.</li>
+   * </ul>
+   * @param skippedCell the cell that was rejected by the time-range, column, or version gate before
+   *                    {@code filterCell} could be consulted
+   * @return a {@link Cell} representing the earliest position the scanner should seek to, or
+   *         {@code null} if this filter cannot provide a better position than the structural hint
+   * @throws IOException in case an I/O or filter-specific failure needs to be signaled
+   * @see #filterCell(Cell)
+   * @see #getNextCellHint(Cell)
+   */
+  public Cell getSkipHint(final Cell skippedCell) throws IOException {
+    return null;
+  }
+
   /**
    * Check that given column family is essential for filter to check row. Most filters always return
    * true here. But some could have more sophisticated logic which could significantly reduce

hbase-client/src/main/java/org/apache/hadoop/hbase/filter/FilterBase.java

@@ -98,6 +98,28 @@ public Cell getNextCellHint(Cell currentCell) throws IOException {
     return null;
   }
 
+  /**
+   * Filters that cannot provide a seek hint after row-key rejection can inherit this no-op
+   * implementation. Subclasses whose row-key logic (e.g. a range pointer advanced inside
+   * {@link #filterRowKey(Cell)}) makes a better seek target available should override this.
+   * {@inheritDoc}
+   */
+  @Override
+  public Cell getHintForRejectedRow(Cell firstRowCell) throws IOException {
+    return null;
+  }
+
+  /**
+   * Filters that cannot provide a structural-skip seek hint can inherit this no-op implementation.
+   * Subclasses with purely configuration-driven, stateless hint computation (e.g. a fixed column
+   * range or fuzzy-row pattern) may override this to avoid cell-by-cell advancement when the
+   * time-range, column, or version gate fires. {@inheritDoc}
+   */
+  @Override
+  public Cell getSkipHint(Cell skippedCell) throws IOException {
+    return null;
+  }
+
   /**
    * By default, we require all scan's column families to be present. Our subclasses may be more
    * precise. {@inheritDoc}

hbase-server/src/main/java/org/apache/hadoop/hbase/filter/FilterWrapper.java

@@ -95,6 +95,26 @@ public Cell getNextCellHint(Cell currentCell) throws IOException {
     return this.filter.getNextCellHint(currentCell);
   }
 
+  /**
+   * Delegates to the wrapped filter's {@link Filter#getHintForRejectedRow(Cell)} so that the scan
+   * pipeline can seek directly past a rejected row rather than iterating cell-by-cell via
+   * {@code nextRow()}. {@inheritDoc}
+   */
+  @Override
+  public Cell getHintForRejectedRow(Cell firstRowCell) throws IOException {
+    return this.filter.getHintForRejectedRow(firstRowCell);
+  }
+
+  /**
+   * Delegates to the wrapped filter's {@link Filter#getSkipHint(Cell)} so that the scan pipeline
+   * can seek ahead when a cell is structurally skipped before {@code filterCell} is reached.
+   * {@inheritDoc}
+   */
+  @Override
+  public Cell getSkipHint(Cell skippedCell) throws IOException {
+    return this.filter.getSkipHint(skippedCell);
+  }
+
   @Override
   public boolean filterRowKey(Cell cell) throws IOException {
     if (filterAllRemaining()) return true;

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RegionScannerImpl.java

@@ -33,6 +33,7 @@
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellComparator;
 import org.apache.hadoop.hbase.CellUtil;
+import org.apache.hadoop.hbase.DoNotRetryIOException;
 import org.apache.hadoop.hbase.ExtendedCell;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.KeyValue;
@@ -86,6 +87,7 @@ public class RegionScannerImpl implements RegionScanner, Shipper, RpcCallback {
 
   protected final byte[] stopRow;
   protected final boolean includeStopRow;
+  protected final boolean reversed;
   protected final HRegion region;
   protected final CellComparator comparator;
 
@@ -130,6 +132,7 @@ private static boolean hasNonce(HRegion region, long nonce) {
     defaultScannerContext = ScannerContext.newBuilder().setBatchLimit(scan.getBatch()).build();
     this.stopRow = scan.getStopRow();
     this.includeStopRow = scan.includeStopRow();
+    this.reversed = scan.isReversed();
     this.operationId = scan.getId();
 
     // synchronize on scannerReadPoints so that nobody calculates
@@ -504,11 +507,18 @@ private boolean nextInternal(List<? super ExtendedCell> results, ScannerContext
           if (isFilterDoneInternal()) {
             return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
           }
+          // HBASE-29974: ask the filter for a seek hint so we can jump directly past the rejected
+          // row instead of iterating through its cells one-by-one via nextRow().
+          ExtendedCell rowHint = getHintForRejectedRow(current);
           // Typically the count of rows scanned is incremented inside #populateResult. However,
           // here we are filtering a row based purely on its row key, preventing us from calling
-          // #populateResult. Thus, perform the necessary increment here to rows scanned metric
+          // #populateResult. Thus, perform the necessary increment here to rows scanned metric.
+          // Placed after getHintForRejectedRow so that a buggy filter throwing DNRIOE doesn't
+          // leave the metric incremented for a row that was never actually processed.
           incrementCountOfRowsScannedMetric(scannerContext);
-          boolean moreRows = nextRow(scannerContext, current);
+          boolean moreRows = (rowHint != null)
+            ? nextRowViaHint(scannerContext, current, rowHint)
+            : nextRow(scannerContext, current);
           if (!moreRows) {
             return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
           }
@@ -750,6 +760,94 @@ protected boolean nextRow(ScannerContext scannerContext, Cell curRowCell) throws
       || this.region.getCoprocessorHost().postScannerFilterRow(this, curRowCell);
   }
 
+  /**
+   * Fast-path alternative to {@link #nextRow} used when the filter has provided a seek hint via
+   * {@link org.apache.hadoop.hbase.filter.Filter#getHintForRejectedRow(Cell)}. Instead of iterating
+   * through every cell in the rejected row one-by-one, this method issues a single seek to jump
+   * directly to the filter's suggested position ({@code requestSeek} for forward scans,
+   * {@code backwardSeek} for reversed scans).
+   * <p>
+   * The skipping-row mode flag is set around the seek so that block-level size tracking continues
+   * to function (consistent with {@link #nextRow}), and the filter state is reset afterwards so the
+   * next row starts with a clean filter context.
+   * <p>
+   * <strong>Stop-row invariant:</strong> This method does not validate that {@code hint} falls
+   * within the scan's stop row. If the hint overshoots, the next iteration's
+   * {@link #shouldStop(Cell)} check catches it and returns NO_MORE_VALUES. One wasted seek may
+   * occur, but correctness is maintained.
+   * <p>
+   * <strong>Metrics note:</strong> The rows-scanned metric is incremented once by the caller for
+   * the rejected row. Rows physically skipped by the seek are not individually counted — this
+   * reflects the fact that no per-row work was done for those rows.
+   * <p>
+   * <strong>Coprocessor note:</strong> {@code postScannerFilterRow} is invoked once with
+   * {@code curRowCell}, not once per skipped row. Coprocessors counting filtered rows should be
+   * aware of this semantic when the hint path is used.
+   * @param scannerContext scanner context used for limit tracking
+   * @param curRowCell     the first cell of the row that was rejected by {@code filterRowKey};
+   *                       passed to the coprocessor hook for observability
+   * @param hint           the validated {@link ExtendedCell} returned by the filter; the scanner
+   *                       will seek to this position
+   * @return {@code true} if scanning should continue, {@code false} if a coprocessor requests an
+   *         early stop (mirrors the contract of {@link #nextRow})
+   * @throws IOException if the seek or the coprocessor hook signals a failure
+   */
+  private boolean nextRowViaHint(ScannerContext scannerContext, Cell curRowCell, ExtendedCell hint)
+    throws IOException {
+    assert this.joinedContinuationRow == null : "Trying to go to next row during joinedHeap read.";
+
+    int difference = comparator.compareRows(hint, curRowCell);
+    if ((!reversed && difference > 0) || (reversed && difference < 0)) {
+      scannerContext.setSkippingRow(true);
+      if (reversed) {
+        // ReversedKeyValueHeap does not support requestSeek; use backwardSeek
+        // to position at-or-before the hint within the target row.
+        // seekToPreviousRow would skip past the hint row entirely.
+        this.storeHeap.backwardSeek(hint);
+      } else {
+        this.storeHeap.requestSeek(hint, true, true);
+      }
+      scannerContext.setSkippingRow(false);
+
+      resetFilters();
+
+      return this.region.getCoprocessorHost() == null
+        || this.region.getCoprocessorHost().postScannerFilterRow(this, curRowCell);
+    }
+
+    return nextRow(scannerContext, curRowCell);
+  }
+
+  /**
+   * Asks the current {@link org.apache.hadoop.hbase.filter.FilterWrapper} for a seek hint to use
+   * after a row has been rejected by {@link #filterRowKey}. If the wrapped filter overrides
+   * {@link org.apache.hadoop.hbase.filter.Filter#getHintForRejectedRow(Cell)}, this returns its
+   * answer as an {@link ExtendedCell}; otherwise returns {@code null}.
+   * <p>
+   * The returned cell is validated to be an {@link ExtendedCell} because filters run on the server
+   * side and the scanner infrastructure requires {@code ExtendedCell} references.
+   * @param rowCell the first cell of the rejected row (same cell passed to {@code filterRowKey})
+   * @return a validated {@link ExtendedCell} seek target, or {@code null} if the filter provides no
+   *         hint
+   * @throws DoNotRetryIOException if the filter returns a non-{@link ExtendedCell} instance
+   * @throws IOException           if the filter signals an I/O failure
+   */
+  private ExtendedCell getHintForRejectedRow(Cell rowCell) throws IOException {
+    if (filter == null) {
+      return null;
+    }
+    Cell hint = filter.getHintForRejectedRow(rowCell);
+    if (hint == null) {
+      return null;
+    }
+    if (!(hint instanceof ExtendedCell)) {
+      throw new DoNotRetryIOException(
+        "Incorrect filter implementation: the Cell returned by getHintForRejectedRow "
+          + "is not an ExtendedCell. Filter class: " + filter.getClass().getName());
+    }
+    return (ExtendedCell) hint;
+  }
+
   protected boolean shouldStop(Cell currentRowCell) {
     if (currentRowCell == null) {
       return true;