Improve precision of CURRENT_TIMESTAMP on Java 9+ and change its return type to…

Improve precision of CURRENT_TIMESTAMP on Java 9+ and change its return type to required by standard

h2/src/docsrc/help/help.csv

@@ -3956,8 +3956,13 @@ CURRENT_TIME()
 { CURRENT_TIMESTAMP [ ( [ int ] ) ] | NOW( [ int ] ) }
 ","
 Returns the current timestamp.
-The precision parameter for nanoseconds precision is optional.
-This method always returns the same value within a transaction.
+If fractional seconds precision is specified it should be from 0 to 9, 9 is default.
+The specified value can be used only to limit precision of a result.
+The actual maximum available precision depends on operating system and JVM and can be 3 (milliseconds) or higher.
+Higher precision is not available before Java 9.
+CURRENT_TIMESTAMP returns timestamp with time zone, its time zone offset is set to a current time zone offset.
+NOW() returns the local timestamp without time zone information.
+These methods always return the same value within a transaction.
 ","
 CURRENT_TIMESTAMP()
 "

h2/src/java9/src/org/h2/util/CurrentTimestamp.java

+/*
+ * Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
+ * and the EPL 1.0 (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.util;
+
+import java.time.Instant;
+
+import org.h2.value.ValueTimestampTimeZone;
+
+public final class CurrentTimestamp {
+
+    /**
+     * Returns current timestamp.
+     *
+     * @return current timestamp
+     */
+    public static ValueTimestampTimeZone get() {
+        Instant now = Instant.now();
+        long second = now.getEpochSecond();
+        int nano = now.getNano();
+        /*
+         * This code intentionally does not support properly dates before UNIX
+         * epoch and time zone offsets with seconds because such support is not
+         * required for current dates.
+         */
+        int offsetSec = DateTimeUtils.getTimeZone().getOffset(second * 1_000 + nano / 1_000_000) / 1000;
+        second += offsetSec;
+        return ValueTimestampTimeZone.fromDateValueAndNanos(
+                DateTimeUtils.dateValueFromAbsoluteDay(second / DateTimeUtils.SECONDS_PER_DAY),
+                second % DateTimeUtils.SECONDS_PER_DAY * 1_000_000_000 + nano, (short) (offsetSec / 60));
+    }
+
+    private CurrentTimestamp() {
+    }
+
+}

h2/src/main/org/h2/engine/Session.java

@@ -48,6 +48,7 @@ import org.h2.table.Table;
 import org.h2.table.TableFilter;
 import org.h2.table.TableType;
 import org.h2.util.ColumnNamerConfiguration;
+import org.h2.util.CurrentTimestamp;
 import org.h2.util.SmallLRUCache;
 import org.h2.util.Utils;
 import org.h2.value.Value;
@@ -55,6 +56,7 @@ import org.h2.value.ValueArray;
 import org.h2.value.ValueLong;
 import org.h2.value.ValueNull;
 import org.h2.value.ValueString;
+import org.h2.value.ValueTimestampTimeZone;
 
 /**
  * A session represents an embedded database connection. When using the server
@@ -114,7 +116,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
     private volatile long cancelAtNs;
     private boolean closed;
     private final long sessionStart = System.currentTimeMillis();
-    private long transactionStart;
+    private ValueTimestampTimeZone transactionStart;
     private long currentCommandStart;
     private HashMap<String, Value> variables;
     private HashSet<ResultInterface> temporaryResults;
@@ -666,7 +668,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
         tablesToAnalyze = null;
 
         currentTransactionName = null;
-        transactionStart = 0;
+        transactionStart = null;
         if (transaction != null) {
             try {
                 // increment the data mod count, so that other sessions
@@ -773,7 +775,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
     public void rollback() {
         checkCommitRollback();
         currentTransactionName = null;
-        transactionStart = 0;
+        transactionStart = null;
         boolean needCommit = undoLog.size() > 0 || transaction != null;
         if(needCommit) {
             rollbackTo(null, false);
@@ -1128,7 +1130,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
     public void rollbackToSavepoint(String name) {
         checkCommitRollback();
         currentTransactionName = null;
-        transactionStart = 0;
+        transactionStart = null;
         if (savepoints == null) {
             throw DbException.get(ErrorCode.SAVEPOINT_IS_INVALID_1, name);
         }
@@ -1453,9 +1455,9 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
         return sessionStart;
     }
 
-    public long getTransactionStart() {
-        if (transactionStart == 0) {
-            transactionStart = System.currentTimeMillis();
+    public ValueTimestampTimeZone getTransactionStart() {
+        if (transactionStart == null) {
+            transactionStart = CurrentTimestamp.get();
         }
         return transactionStart;
     }

h2/src/main/org/h2/expression/Function.java

@@ -63,7 +63,6 @@ import org.h2.value.ValueLong;
 import org.h2.value.ValueNull;
 import org.h2.value.ValueResultSet;
 import org.h2.value.ValueString;
-import org.h2.value.ValueTime;
 import org.h2.value.ValueTimestamp;
 import org.h2.value.ValueTimestampTimeZone;
 import org.h2.value.ValueUuid;
@@ -300,11 +299,11 @@ public class Function extends Expression implements FunctionCall {
         addFunctionNotDeterministic("CURTIME", CURTIME,
                 0, Value.TIME);
         addFunctionNotDeterministic("CURRENT_TIMESTAMP", CURRENT_TIMESTAMP,
-                VAR_ARGS, Value.TIMESTAMP);
+                VAR_ARGS, Value.TIMESTAMP_TZ);
         addFunctionNotDeterministic("SYSDATE", CURRENT_TIMESTAMP,
-                VAR_ARGS, Value.TIMESTAMP);
+                VAR_ARGS, Value.TIMESTAMP_TZ);
         addFunctionNotDeterministic("SYSTIMESTAMP", CURRENT_TIMESTAMP,
-                VAR_ARGS, Value.TIMESTAMP);
+                VAR_ARGS, Value.TIMESTAMP_TZ);
         addFunctionNotDeterministic("NOW", NOW,
                 VAR_ARGS, Value.TIMESTAMP);
         addFunction("DATEADD", DATE_ADD,
@@ -823,28 +822,22 @@ public class Function extends Expression implements FunctionCall {
         }
         case CURDATE:
         case CURRENT_DATE: {
-            long now = session.getTransactionStart();
-            // need to normalize
-            result = ValueDate.fromMillis(now);
+            result = session.getTransactionStart().convertTo(Value.DATE);
             break;
         }
         case CURTIME:
         case CURRENT_TIME: {
-            long now = session.getTransactionStart();
-            // need to normalize
-            result = ValueTime.fromMillis(now);
+            result = session.getTransactionStart().convertTo(Value.TIME);
+            break;
+        }
+        case NOW: {
+            Value vt = session.getTransactionStart().convertTo(Value.TIMESTAMP);
+            result = v0 == null ? vt : vt.convertScale(false, v0.getInt());
             break;
         }
-        case NOW:
         case CURRENT_TIMESTAMP: {
-            long now = session.getTransactionStart();
-            ValueTimestamp vt = ValueTimestamp.fromMillis(now);
-            if (v0 != null) {
-                Mode mode = database.getMode();
-                vt = (ValueTimestamp) vt.convertScale(
-                        mode.convertOnlyToSmallerScale, v0.getInt());
-            }
-            result = vt;
+            ValueTimestampTimeZone vt = session.getTransactionStart();
+            result = v0 == null ? vt : vt.convertScale(false, v0.getInt());
             break;
         }
         case DATABASE:

h2/src/main/org/h2/table/Column.java

@@ -21,20 +21,16 @@ import org.h2.message.DbException;
 import org.h2.result.Row;
 import org.h2.schema.Schema;
 import org.h2.schema.Sequence;
-import org.h2.util.DateTimeUtils;
 import org.h2.util.MathUtils;
 import org.h2.util.StringUtils;
 import org.h2.value.DataType;
 import org.h2.value.Value;
-import org.h2.value.ValueDate;
 import org.h2.value.ValueEnum;
 import org.h2.value.ValueInt;
 import org.h2.value.ValueLong;
 import org.h2.value.ValueNull;
 import org.h2.value.ValueString;
 import org.h2.value.ValueTime;
-import org.h2.value.ValueTimestamp;
-import org.h2.value.ValueTimestampTimeZone;
 import org.h2.value.ValueUuid;
 
 /**
@@ -361,16 +357,13 @@ public class Column {
                     if (dt.decimal) {
                         value = ValueInt.get(0).convertTo(type);
                     } else if (dt.type == Value.TIMESTAMP) {
-                        value = ValueTimestamp.fromMillis(session.getTransactionStart());
+                        value = session.getTransactionStart().convertTo(Value.TIMESTAMP);
                     } else if (dt.type == Value.TIMESTAMP_TZ) {
-                        long ms = session.getTransactionStart();
-                        value = ValueTimestampTimeZone.fromDateValueAndNanos(
-                                DateTimeUtils.dateValueFromDate(ms),
-                                DateTimeUtils.nanosFromDate(ms), (short) 0);
+                        value = session.getTransactionStart();
                     } else if (dt.type == Value.TIME) {
                         value = ValueTime.fromNanos(0);
                     } else if (dt.type == Value.DATE) {
-                        value = ValueDate.fromMillis(session.getTransactionStart());
+                        value = session.getTransactionStart().convertTo(Value.DATE);
                     } else {
                         value = ValueString.get("").convertTo(type);
                     }

h2/src/main/org/h2/util/CurrentTimestamp.java

+/*
+ * Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
+ * and the EPL 1.0 (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.util;
+
+import org.h2.value.ValueTimestampTimeZone;
+
+public final class CurrentTimestamp {
+
+    /*
+     * Signatures of methods should match with
+     * h2/src/java9/src/org/h2/util/CurrentTimestamp.java and precompiled
+     * h2/src/java9/precompiled/org/h2/util/CurrentTimestamp.class.
+     */
+
+    /**
+     * Returns current timestamp.
+     *
+     * @return current timestamp
+     */
+    public static ValueTimestampTimeZone get() {
+        long ms = System.currentTimeMillis();
+        /*
+         * This code intentionally does not support properly dates before UNIX
+         * epoch and time zone offsets with seconds because such support is not
+         * required for current dates.
+         */
+        int offset = DateTimeUtils.getTimeZone().getOffset(ms);
+        ms += offset;
+        return ValueTimestampTimeZone.fromDateValueAndNanos(
+                DateTimeUtils.dateValueFromAbsoluteDay(ms / DateTimeUtils.MILLIS_PER_DAY),
+                ms % DateTimeUtils.MILLIS_PER_DAY * 1_000_000, (short) (offset / 60_000));
+    }
+
+    private CurrentTimestamp() {
+    }
+
+}

h2/src/main/org/h2/util/DateTimeUtils.java

@@ -112,7 +112,7 @@ public class DateTimeUtils {
      *
      * @return local time zone
      */
-    private static TimeZone getTimeZone() {
+    static TimeZone getTimeZone() {
         TimeZone tz = timeZone;
         if (tz == null) {
             timeZone = tz = TimeZone.getDefault();
@@ -506,7 +506,7 @@ public class DateTimeUtils {
                 if (withTimeZone) {
                     if (tz != UTC) {
                         long millis = convertDateTimeValueToMillis(tz, dateValue, nanos / 1_000_000);
-                        tzMinutes = (short) (tz.getOffset(millis) / 1000 / 60);
+                        tzMinutes = (short) (tz.getOffset(millis) / 60_000);
                     }
                 } else {
                     long millis = convertDateTimeValueToMillis(tz, dateValue, nanos / 1_000_000);