jpountz commented on code in PR #12841:
URL: https://github.com/apache/lucene/pull/12841#discussion_r1404341416
##########
lucene/core/src/java21/org/apache/lucene/store/MemorySegmentIndexInput.java:
##########
@@ -303,6 +304,30 @@ public byte readByte(long pos) throws IOException {
}
}
+ @Override
+ public void readGroupVInt(long[] docs, int pos) throws IOException {
+ if (curSegment.byteSize() - curPosition < 17) {
+ super.readGroupVInt(docs, pos);
+ return;
+ }
+
+ final int flag = readByte() & 0xFF;
+
+ final int n1Minus1 = flag >> 6;
+ final int n2Minus1 = (flag >> 4) & 0x03;
+ final int n3Minus1 = (flag >> 2) & 0x03;
+ final int n4Minus1 = flag & 0x03;
+
+ docs[pos] = curSegment.get(LAYOUT_LE_INT, curPosition) & MASKS[n1Minus1];
+ curPosition += 1 + n1Minus1;
+ docs[pos + 1] = curSegment.get(LAYOUT_LE_INT, curPosition) &
MASKS[n2Minus1];
+ curPosition += 1 + n2Minus1;
+ docs[pos + 2] = curSegment.get(LAYOUT_LE_INT, curPosition) &
MASKS[n3Minus1];
+ curPosition += 1 + n3Minus1;
+ docs[pos + 3] = curSegment.get(LAYOUT_LE_INT, curPosition) &
MASKS[n4Minus1];
+ curPosition += 1 + n4Minus1;
+ }
Review Comment:
Can you add the same `catch (NullPointerException | IllegalStateException
e)` that `readInt()` and other read methods have, for the case when the index
input is closed?
##########
lucene/core/src/java21/org/apache/lucene/store/MemorySegmentIndexInput.java:
##########
@@ -303,6 +304,30 @@ public byte readByte(long pos) throws IOException {
}
}
+ @Override
+ public void readGroupVInt(long[] docs, int pos) throws IOException {
+ if (curSegment.byteSize() - curPosition < 17) {
+ super.readGroupVInt(docs, pos);
+ return;
+ }
Review Comment:
I don't think we have a test that covers this case well at the moment.
##########
lucene/core/src/java21/org/apache/lucene/store/MemorySegmentIndexInput.java:
##########
@@ -49,6 +49,7 @@ abstract class MemorySegmentIndexInput extends IndexInput
implements RandomAcces
final int chunkSizePower;
final Arena arena;
final MemorySegment[] segments;
+ private static final int[] MASKS = new int[] {0xFF, 0xFFFF, 0xFFFFFF,
0xFFFFFFFF};
Review Comment:
maybe rename to `GROUP_VINT_MASKS` or something along these lines now that
this logic moved to a class which is not only about group vint?
Also in general I prefer having constants before instance members in the
class definition.
##########
lucene/core/src/java/org/apache/lucene/store/DataOutput.java:
##########
@@ -29,6 +29,7 @@
* internal state like file position).
*/
public abstract class DataOutput {
+ BytesRef groupVIntBytes;
Review Comment:
BytesRefBuilder feels like a better fit for how you're using it (using
`length` rather than `offset` to track the number of written bytes). Also let's
make it `private`?
##########
lucene/core/src/test/org/apache/lucene/codecs/lucene99/TestGroupVInt.java:
##########
@@ -31,9 +34,7 @@ public void testEncodeDecode() throws IOException {
long[] values = new long[ForUtil.BLOCK_SIZE];
long[] restored = new long[ForUtil.BLOCK_SIZE];
final int iterations = atLeast(100);
-
- final GroupVIntWriter w = new GroupVIntWriter();
- byte[] encoded = new byte[(int) (Integer.BYTES * ForUtil.BLOCK_SIZE *
1.25)];
+ Directory dir = FSDirectory.open(createTempDir());
Review Comment:
Let's use `newFSDirectory` to add coverage for all Directory implementations?
```suggestion
Directory dir = newFSDirectory(createTempDir());
```
##########
lucene/core/src/java/org/apache/lucene/store/DataOutput.java:
##########
@@ -324,4 +325,45 @@ public void writeSetOfStrings(Set<String> set) throws
IOException {
writeString(value);
}
}
+
+ /**
+ * Encode integers using group-varint. It uses VInt to encode tail values
that are not enough for
+ * a group
+ *
+ * @param values the values to write
+ * @param limit the number of values to write.
+ */
+ public void writeGroupVInts(long[] values, int limit) throws IOException {
+ if (groupVIntBytes == null) {
+ // the maximum size of one group is 4 integers + 1 byte flag.
+ groupVIntBytes = new BytesRef(17);
+ }
+ int off = 0;
+
+ // encode each group
+ while ((limit - off) >= 4) {
+ byte flag = 0;
+ groupVIntBytes.offset = 1;
+ flag |= (encodeGroupValue((int) values[off++]) - 1) << 6;
+ flag |= (encodeGroupValue((int) values[off++]) - 1) << 4;
+ flag |= (encodeGroupValue((int) values[off++]) - 1) << 2;
+ flag |= (encodeGroupValue((int) values[off++]) - 1);
+ groupVIntBytes.bytes[0] = flag;
+ writeBytes(groupVIntBytes.bytes, groupVIntBytes.offset);
+ }
+
+ // tail vints
+ for (; off < limit; off++) {
+ writeVInt((int) values[off]);
Review Comment:
Now that we're moving this to `DataOutput`, we probably need to check these
casts, e.g. with `Math.toIntExact`.
##########
lucene/core/src/java/org/apache/lucene/store/DataInput.java:
##########
@@ -98,6 +98,55 @@ public int readInt() throws IOException {
return ((b4 & 0xFF) << 24) | ((b3 & 0xFF) << 16) | ((b2 & 0xFF) << 8) |
(b1 & 0xFF);
}
+ /**
+ * Read all the group varints, including the tail vints.
+ *
+ * @param docs the array to read ints into.
+ * @param limit the number of int values to read.
+ */
+ public void readGroupVInts(long[] docs, int limit) throws IOException {
+ int i;
+ for (i = 0; i <= limit - 4; i += 4) {
+ readGroupVInt(docs, i);
+ }
+ for (; i < limit; ++i) {
+ docs[i] = readVInt();
+ }
+ }
+
+ /**
+ * Read single group varint. we need a long[] because this is what postings
are using.
+ *
+ * @param docs the array to read ints into.
+ * @param offset the offset in the array to start storing ints.
+ */
+ public void readGroupVInt(long[] docs, int offset) throws IOException {
Review Comment:
Let's make this method private? This would force `MemorySegmentIndexInput`
to copy the logic of `readGroupVInts` but this would also be better
encapsulated?
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