Make sure to handle microsecond resolution as PostgreSQL does

Fixes #1165

PostgreSQL has microsecond resolution for timestamps.
When converting from text, if the nanoseconds part after microseconds is strictly bigger than 499, PostgreSQL server rounds up to the next microsecond.

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

Author: tsegismont

vertx-pg-client/src/main/java/io/vertx/pgclient/impl/codec/DataTypeCodec.java

@@ -22,12 +22,12 @@
 import io.netty.buffer.Unpooled;
 import io.netty.handler.codec.DecoderException;
 import io.vertx.core.buffer.Buffer;
+import io.vertx.core.internal.buffer.BufferInternal;
 import io.vertx.core.internal.logging.Logger;
 import io.vertx.core.internal.logging.LoggerFactory;
 import io.vertx.core.json.Json;
 import io.vertx.core.json.JsonArray;
 import io.vertx.core.json.JsonObject;
-import io.vertx.core.internal.buffer.BufferInternal;
 import io.vertx.pgclient.data.*;
 import io.vertx.pgclient.impl.util.UTF8StringEndDetector;
 import io.vertx.sqlclient.Tuple;
@@ -1086,6 +1086,13 @@ private static OffsetTime textDecodeTIMETZ(int index, int len, ByteBuf buff) {
       DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss G", Locale.US));
 
   private static void binaryEncodeTIMESTAMP(LocalDateTime value, ByteBuf buff) {
+    // Make sure to handle microsecond resolution as PostgreSQL does when it converts textual representation of timestamps.
+    // Over 499 nanos after the microsecond, round up to the next microsecond.
+    // Otherwise, do nothing and the nanos after the microsecond will be truncated below.
+    int nanosAfterMicro = value.getNano() % 1000;
+    if (nanosAfterMicro > 499) {
+      value = value.plusNanos(1000 - nanosAfterMicro);
+    }
     if (value.compareTo(LDT_PLUS_INFINITY) >= 0) {
       value = LDT_PLUS_INFINITY;
     } else if (value.compareTo(LDT_MINUS_INFINITY) <= 0) {

vertx-pg-client/src/test/java/io/vertx/tests/pgclient/data/DateTimeTypesExtendedCodecTest.java

@@ -4,9 +4,9 @@
 import io.vertx.ext.unit.TestContext;
 import io.vertx.pgclient.PgConnection;
 import io.vertx.pgclient.data.Interval;
-import io.vertx.tests.sqlclient.ColumnChecker;
 import io.vertx.sqlclient.Row;
 import io.vertx.sqlclient.Tuple;
+import io.vertx.tests.sqlclient.ColumnChecker;
 import org.junit.Test;
 
 import java.time.*;
@@ -628,4 +628,35 @@ private <T> void testDecodeDataTimeGeneric(TestContext ctx,
         }));
     }));
   }
+
+  @Test
+  public void testClientHandlesTimestampResolutionLikeServer(TestContext ctx) {
+    // PostgreSQL has microsecond resolution for timestamps.
+    // When converting from text, if the nanoseconds part after microseconds is strictly bigger than 499,
+    // PostgreSQL server rounds up to the next microsecond.
+    Async over499 = ctx.async();
+    PgConnection.connect(vertx, options).onComplete(ctx.asyncAssertSuccess(conn -> {
+      conn.prepare("SELECT '2025-12-31 23:59:59.999999773'::timestamp WHERE '2025-12-31 23:59:59.999999773'::timestamp = $1::timestamp").onComplete(
+        ctx.asyncAssertSuccess(p -> {
+          p.query()
+            .execute(Tuple.of(LocalDateTime.parse("2025-12-31T23:59:59.999999773"))).onComplete(ctx.asyncAssertSuccess(result -> {
+              ctx.assertEquals(1, result.size());
+              ctx.assertEquals(LocalDateTime.parse("2026-01-01T00:00:00.000000"), result.iterator().next().getLocalDateTime(0));
+              over499.complete();
+            }));
+        }));
+    }));
+    Async under499 = ctx.async();
+    PgConnection.connect(vertx, options).onComplete(ctx.asyncAssertSuccess(conn -> {
+      conn.prepare("SELECT '2025-12-31 23:59:59.999999227'::timestamp WHERE '2025-12-31 23:59:59.999999227'::timestamp = $1::timestamp").onComplete(
+        ctx.asyncAssertSuccess(p -> {
+          p.query()
+            .execute(Tuple.of(LocalDateTime.parse("2025-12-31T23:59:59.999999227"))).onComplete(ctx.asyncAssertSuccess(result -> {
+              ctx.assertEquals(1, result.size());
+              ctx.assertEquals(LocalDateTime.parse("2025-12-31T23:59:59.999999"), result.iterator().next().getLocalDateTime(0));
+              under499.complete();
+            }));
+        }));
+    }));
+  }
 }