Revert "Binary search the entries when all suffixes have the same length in a leaf block. (#11722)"

This reverts commit 3adec5b1ce.

lucene/CHANGES.txt

@@ -112,9 +112,6 @@ Improvements
 
 * GITHUB#687: speed up IndexSortSortedNumericDocValuesRangeQuery#BoundedDocIdSetIterator
   construction using bkd binary search. (Jianping Weng)
-  
-* GITHUB#11722: Binary search the entries when all suffixes have the same length
-  in a leaf block of the terms dictionary. (zhouhui)
 
 Bug Fixes
 ---------------------

lucene/core/src/java/org/apache/lucene/codecs/lucene90/blocktree/SegmentTermsEnumFrame.java

@@ -75,9 +75,6 @@ final class SegmentTermsEnumFrame {
   // True if all entries are terms
   boolean isLeafBlock;
 
-  // True if all entries have the same length.
-  boolean allEqual;
-
   long lastSubFP;
 
   int nextFloorLabel;
@@ -190,7 +187,7 @@ final class SegmentTermsEnumFrame {
     suffixesReader.reset(suffixBytes, 0, numSuffixBytes);
 
     int numSuffixLengthBytes = ste.in.readVInt();
-    allEqual = (numSuffixLengthBytes & 0x01) != 0;
+    final boolean allEqual = (numSuffixLengthBytes & 0x01) != 0;
     numSuffixLengthBytes >>>= 1;
     if (suffixLengthBytes.length < numSuffixLengthBytes) {
       suffixLengthBytes = new byte[ArrayUtil.oversize(numSuffixLengthBytes, 1)];
@@ -530,9 +527,7 @@ final class SegmentTermsEnumFrame {
 
   // NOTE: sets startBytePos/suffix as a side effect
   public SeekStatus scanToTerm(BytesRef target, boolean exactOnly) throws IOException {
-    return isLeafBlock
-        ? allEqual ? binarySearchTermLeaf(target, exactOnly) : scanToTermLeaf(target, exactOnly)
-        : scanToTermNonLeaf(target, exactOnly);
+    return isLeafBlock ? scanToTermLeaf(target, exactOnly) : scanToTermNonLeaf(target, exactOnly);
   }
 
   private int startBytePos;
@@ -577,6 +572,8 @@ final class SegmentTermsEnumFrame {
 
     assert prefixMatches(target);
 
+    // TODO: binary search when all terms have the same length, which is common for ID fields,
+    // which are also the most sensitive to lookup performance?
     // Loop over each entry (term or sub-block) in this block:
     do {
       nextEnt++;
@@ -649,94 +646,6 @@ final class SegmentTermsEnumFrame {
     return SeekStatus.END;
   }
 
-  // Target's prefix matches this block's prefix;
-  // And all suffixes have the same length in this block,
-  // we binary search the entries check if the suffix matches.
-  public SeekStatus binarySearchTermLeaf(BytesRef target, boolean exactOnly) throws IOException {
-    // if (DEBUG) System.out.println("    binarySearchTermLeaf: block fp=" + fp + " prefix=" +
-    // prefix + "
-    // nextEnt=" + nextEnt + " (of " + entCount + ") target=" + brToString(target) + " term=" +
-    // brToString(term));
-
-    assert nextEnt != -1;
-
-    ste.termExists = true;
-    subCode = 0;
-
-    if (nextEnt == entCount) {
-      if (exactOnly) {
-        fillTerm();
-      }
-      return SeekStatus.END;
-    }
-
-    assert prefixMatches(target);
-
-    suffix = suffixLengthsReader.readVInt();
-    int start = nextEnt;
-    int end = entCount - 1;
-    // Binary search the entries (terms) in this leaf block:
-    int cmp = 0;
-    while (start <= end) {
-      int mid = (start + end) / 2;
-      nextEnt = mid + 1;
-      startBytePos = mid * suffix;
-      suffixesReader.setPosition(startBytePos + suffix);
-
-      // Binary search bytes in the suffix, comparing to the target
-      cmp =
-          Arrays.compareUnsigned(
-              suffixBytes,
-              startBytePos,
-              startBytePos + suffix,
-              target.bytes,
-              target.offset + prefix,
-              target.offset + target.length);
-      if (cmp < 0) {
-        start = mid + 1;
-      } else if (cmp > 0) {
-        end = mid - 1;
-      } else {
-        // Exact match!
-
-        // This cannot be a sub-block because we
-        // would have followed the index to this
-        // sub-block from the start:
-
-        assert ste.termExists;
-        fillTerm();
-        // if (DEBUG) System.out.println("        found!");
-        return SeekStatus.FOUND;
-      }
-    }
-
-    // It is possible (and OK) that terms index pointed us
-    // at this block, but, we searched the entire block and
-    // did not find the term to position to.  This happens
-    // when the target is after the last term in the block
-    // (but, before the next term in the index).  EG
-    // target could be foozzz, and terms index pointed us
-    // to the foo* block, but the last term in this block
-    // was fooz (and, eg, first term in the next block will
-    // bee fop).
-    // if (DEBUG) System.out.println("      block end");
-    SeekStatus seekStatus = end < entCount - 1 ? SeekStatus.NOT_FOUND : SeekStatus.END;
-    if (exactOnly || seekStatus == SeekStatus.NOT_FOUND) {
-      // If binary search ended at the less term, we need to advance to the greater term.
-      if (cmp < 0) {
-        startBytePos += suffix;
-        suffixesReader.skipBytes(suffix);
-        nextEnt++;
-      }
-      fillTerm();
-    }
-
-    // TODO: not consistent that in the
-    // not-exact case we don't next() into the next
-    // frame here
-    return seekStatus;
-  }
-
   // Target's prefix matches this block's prefix; we
   // scan the entries check if the suffix matches.
   public SeekStatus scanToTermNonLeaf(BytesRef target, boolean exactOnly) throws IOException {

lucene/test-framework/src/java/org/apache/lucene/tests/index/BasePostingsFormatTestCase.java

@@ -367,57 +367,6 @@ public abstract class BasePostingsFormatTestCase extends BaseIndexFileFormatTest
     dir.close();
   }
 
-  public void testBinarySearchTermLeaf() throws Exception {
-    Directory dir = newDirectory();
-
-    IndexWriterConfig iwc = newIndexWriterConfig(null);
-    iwc.setCodec(getCodec());
-    iwc.setMergePolicy(newTieredMergePolicy());
-    IndexWriter iw = new IndexWriter(dir, iwc);
-
-    for (int i = 100000; i <= 100400; i++) {
-      // only add odd number
-      if (i % 2 == 1) {
-        Document document = new Document();
-        document.add(new StringField("id", i + "", Field.Store.NO));
-        iw.addDocument(document);
-      }
-    }
-    iw.commit();
-    iw.forceMerge(1);
-
-    DirectoryReader reader = DirectoryReader.open(iw);
-    TermsEnum termsEnum = getOnlyLeafReader(reader).terms("id").iterator();
-    // test seekExact
-    for (int i = 100000; i <= 100400; i++) {
-      BytesRef target = new BytesRef(i + "");
-      if (i % 2 == 1) {
-        assertTrue(termsEnum.seekExact(target));
-        assertEquals(termsEnum.term(), target);
-      } else {
-        assertFalse(termsEnum.seekExact(target));
-      }
-    }
-    // test seekCeil
-    for (int i = 100000; i < 100400; i++) {
-      BytesRef target = new BytesRef(i + "");
-      if (i % 2 == 1) {
-        assertEquals(SeekStatus.FOUND, termsEnum.seekCeil(target));
-        assertEquals(termsEnum.term(), target);
-        if (i <= 100397) {
-          assertEquals(new BytesRef(i + 2 + ""), termsEnum.next());
-        }
-      } else {
-        assertEquals(SeekStatus.NOT_FOUND, termsEnum.seekCeil(target));
-        assertEquals(new BytesRef(i + 1 + ""), termsEnum.term());
-      }
-    }
-    assertEquals(SeekStatus.END, termsEnum.seekCeil(new BytesRef(100400 + "")));
-    reader.close();
-    iw.close();
-    dir.close();
-  }
-
   // tests that level 2 ghost fields still work
   public void testLevel2Ghosts() throws Exception {
     Directory dir = newDirectory();