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Add explicit FieldValue canonicalization #1178

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Merged
merged 7 commits into from
Feb 1, 2020
Merged

Add explicit FieldValue canonicalization #1178

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9ad59dc
Add explicit FieldValue canonicalization
schmidt-sebastian Jan 30, 2020
a3f3b79
Feedback
schmidt-sebastian Jan 31, 2020
cc39419
Update ProtoValues.java
schmidt-sebastian Jan 31, 2020
2ef1826
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schmidt-sebastian Jan 31, 2020
b3b6a77
Merge
schmidt-sebastian Jan 31, 2020
5b1d303
Update ProtoValues.java
schmidt-sebastian Feb 1, 2020
51d8684
Revert Collections.sort()
schmidt-sebastian Feb 1, 2020
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89 changes: 89 additions & 0 deletions firebase-firestore/src/main/java/com/google/firebase/firestore/model/value/ProtoValues.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

// TODO(mrschmidt): Make package-private
Expand Down Expand Up @@ -249,4 +250,92 @@ private static int compareMaps(MapValue left, MapValue right) {
// Only equal if both iterators are exhausted.
return Util.compareBooleans(iterator1.hasNext(), iterator2.hasNext());
}

/** Generate the canonical ID for the provided field value (as used in Target serialization). */
public static String canonicalId(Value value) {
StringBuilder builder = new StringBuilder();
stringifyValue(builder, value);
return builder.toString();
}

// TODO(mrschmidt): Use in target serialization and migrate all existing TargetData
private static void stringifyValue(StringBuilder builder, Value value) {
switch (value.getValueTypeCase()) {
case NULL_VALUE:
builder.append("null");
break;
case BOOLEAN_VALUE:
builder.append(value.getBooleanValue());
break;
case INTEGER_VALUE:
builder.append(value.getIntegerValue());
break;
case DOUBLE_VALUE:
builder.append(value.getDoubleValue());
break;
case TIMESTAMP_VALUE:
stringifyTimestamp(builder, value.getTimestampValue());
break;
case STRING_VALUE:
builder.append(value.getStringValue());
break;
case BYTES_VALUE:
builder.append(Util.toDebugString(value.getBytesValue()));
break;
case REFERENCE_VALUE:
// TODO(mrschmidt): Use document key only
builder.append(value.getReferenceValue());
break;
case GEO_POINT_VALUE:
stringifyGeoPoint(builder, value.getGeoPointValue());
break;
case ARRAY_VALUE:
stringifyArray(builder, value.getArrayValue());
break;
case MAP_VALUE:
stringifyObject(builder, value.getMapValue());
break;
default:
throw fail("Invalid value type: " + value.getValueTypeCase());
}
}

private static void stringifyTimestamp(StringBuilder builder, Timestamp timestamp) {
builder.append(String.format("time(%s,%s)", timestamp.getSeconds(), timestamp.getNanos()));
}

private static void stringifyGeoPoint(StringBuilder builder, LatLng latLng) {
builder.append(String.format("geo(%s,%s)", latLng.getLatitude(), latLng.getLongitude()));
}

private static void stringifyObject(StringBuilder builder, MapValue mapValue) {
// Even though MapValue are likely sorted correctly based on their insertion order (e.g. when
// received from the backend), local modifications can bring elements out of order. We need to
// re-sort the elements to ensure that canonical IDs are independent of insertion order.
SortedMap<String, Value> sortedMap = new TreeMap<>(mapValue.getFieldsMap());
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Building a binary tree to sort the entries is pretty wasteful in terms of memory allocation. It's also pessimistic because building the tree is always going to cost O(n lg(n)). An alternative would be to collect the keys into an ArrayList and sort that. That has the benefit of allocating less memory and also runs in O(n) if the list is already sorted.

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I went through different implementations for optimize for both runtime complexity and readability. While I still think that using large Maps here is kind of an anti-pattern (especially given our lack of truncation support), adding an extra line here to pre-sort the keys (and performing a key-based lookup on the HashMap) might be a worthy tradeoff. Updated.


builder.append("{");
boolean first = true;
for (Map.Entry<String, Value> entry : sortedMap.entrySet()) {
if (!first) {
builder.append(",");
} else {
first = false;
}
builder.append(entry.getKey()).append(":");
stringifyValue(builder, entry.getValue());
}
builder.append("}");
}

private static void stringifyArray(StringBuilder builder, ArrayValue arrayValue) {
builder.append("[");
for (int i = 0; i < arrayValue.getValuesCount(); ++i) {
stringifyValue(builder, arrayValue.getValues(i));
if (i != arrayValue.getValuesCount() - 1) {
builder.append(",");
}
}
builder.append("]");
}
}
31 changes: 31 additions & 0 deletions firebase-firestore/src/test/java/com/google/firebase/firestore/model/FieldValueTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
import com.google.firebase.firestore.model.protovalue.ObjectValue;
import com.google.firebase.firestore.model.protovalue.PrimitiveValue;
import com.google.firebase.firestore.model.value.FieldValue;
import com.google.firebase.firestore.model.value.ProtoValues;
import com.google.firebase.firestore.model.value.ServerTimestampValue;
import com.google.firebase.firestore.testutil.ComparatorTester;
import com.google.firestore.v1.Value;
Expand Down Expand Up @@ -366,6 +367,36 @@ public void testValueOrdering() {
.testCompare();
}

@Test
public void testCanonicalIds() {
assertCanonicalId(wrap(null), "null");
assertCanonicalId(wrap(true), "true");
assertCanonicalId(wrap(false), "false");
assertCanonicalId(wrap(1), "1");
assertCanonicalId(wrap(1.0), "1.0");
assertCanonicalId(wrap(new Timestamp(30, 60)), "time(30,60)");
assertCanonicalId(wrap("a"), "a");
assertCanonicalId(wrap(blob(1, 2, 3)), "010203");
assertCanonicalId(
wrapRef(dbId("p1", "d1"), key("c1/doc1")), "projects/p1/databases/d1/documents/c1/doc1");
assertCanonicalId(wrap(new GeoPoint(30, 60)), "geo(30.0,60.0)");
assertCanonicalId(wrap(Arrays.asList(1, 2, 3)), "[1,2,3]");
assertCanonicalId(wrap(map("a", 1, "b", 2, "c", "3")), "{a:1,b:2,c:3}");
assertCanonicalId(
wrap(map("a", Arrays.asList("b", map("c", new GeoPoint(30, 60))))),
"{a:[b,{c:geo(30.0,60.0)}]}");
}

@Test
public void testObjectCanonicalIdsIgnoreSortOrder() {
assertCanonicalId(wrap(map("a", 1, "b", 2, "c", "3")), "{a:1,b:2,c:3}");
assertCanonicalId(wrap(map("c", 3, "b", 2, "a", "1")), "{a:1,b:2,c:3}");
}

private void assertCanonicalId(PrimitiveValue fieldValue, String expectedCanonicalId) {
assertEquals(expectedCanonicalId, ProtoValues.canonicalId(fieldValue.toProto()));
}

private ObjectValue setField(ObjectValue objectValue, String fieldPath, PrimitiveValue value) {
return objectValue.toBuilder().set(field(fieldPath), value.toProto()).build();
}
Expand Down