Rework on now function implementation

common/src/main/java/org/opensearch/sql/common/utils/QueryContext.java

@@ -24,11 +24,6 @@ public class QueryContext {
    */
   private static final String REQUEST_ID_KEY = "request_id";
 
-  /**
-   * Timestamp when SQL plugin started to process current request.
-   */
-  private static final String REQUEST_PROCESSING_STARTED = "request_processing_started";
-
   /**
    * Generates a random UUID and adds to the {@link ThreadContext} as the request id.
    * <p>
@@ -56,22 +51,6 @@ public static String getRequestId() {
     return id;
   }
 
-  public static void recordProcessingStarted() {
-    ThreadContext.put(REQUEST_PROCESSING_STARTED, LocalDateTime.now().toString());
-  }
-
-  /**
-   * Get recorded previously time indicating when processing started for the current query.
-   * @return A LocalDateTime object
-   */
-  public static LocalDateTime getProcessingStartedTime() {
-    if (ThreadContext.containsKey(REQUEST_PROCESSING_STARTED)) {
-      return LocalDateTime.parse(ThreadContext.get(REQUEST_PROCESSING_STARTED));
-    }
-    // This shouldn't happen outside of unit tests
-    return LocalDateTime.now();
-  }
-
   /**
    * Wraps a given instance of {@link Runnable} into a new one which gets all the
    * entries from current ThreadContext map.

core/src/main/java/org/opensearch/sql/analysis/AnalysisContext.java

@@ -7,9 +7,13 @@
 package org.opensearch.sql.analysis;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import lombok.Getter;
+import lombok.Setter;
+import org.opensearch.sql.expression.Expression;
 import org.opensearch.sql.expression.NamedExpression;
 
 /**
@@ -23,13 +27,27 @@ public class AnalysisContext {
   @Getter
   private final List<NamedExpression> namedParseExpressions;
 
+  /**
+   * Storage for values of functions which return a constant value.
+   * We are storing the values there to use it in sequential calls to those functions.
+   * For example, `now` function should the same value during processing a query.
+   */
+  @Getter
+  @Setter
+  private Map<String, Expression> cachedFunctionValues;
+
   public AnalysisContext() {
     this(new TypeEnvironment(null));
   }
 
+  /**
+   * Class CTOR.
+   * @param environment Env to set to a new instance.
+   */
   public AnalysisContext(TypeEnvironment environment) {
     this.environment = environment;
     this.namedParseExpressions = new ArrayList<>();
+    this.cachedFunctionValues = new HashMap<>();
   }
 
   /**

core/src/main/java/org/opensearch/sql/analysis/ExpressionAnalyzer.java

@@ -27,6 +27,7 @@
 import org.opensearch.sql.ast.expression.EqualTo;
 import org.opensearch.sql.ast.expression.Field;
 import org.opensearch.sql.ast.expression.Function;
+import org.opensearch.sql.ast.expression.FunctionWithCachedValue;
 import org.opensearch.sql.ast.expression.HighlightFunction;
 import org.opensearch.sql.ast.expression.In;
 import org.opensearch.sql.ast.expression.Interval;
@@ -169,6 +170,20 @@ public Expression visitRelevanceFieldList(RelevanceFieldList node, AnalysisConte
         ImmutableMap.copyOf(node.getFieldList())));
   }
 
+  @Override
+  public Expression visitFunctionWithCachedValue(FunctionWithCachedValue node,
+                                                 AnalysisContext context) {
+    var valueName = node.toString();
+    if (context.getCachedFunctionValues().containsKey(valueName)) {
+      return context.getCachedFunctionValues().get(valueName);
+    }
+
+    var value = visitFunction(node, context);
+    value = DSL.literal(value.valueOf(null));
+    context.getCachedFunctionValues().put(valueName, value);
+    return value;
+  }
+
   @Override
   public Expression visitFunction(Function node, AnalysisContext context) {
     FunctionName functionName = FunctionName.of(node.getFuncName());

core/src/main/java/org/opensearch/sql/ast/AbstractNodeVisitor.java

@@ -18,6 +18,7 @@
 import org.opensearch.sql.ast.expression.EqualTo;
 import org.opensearch.sql.ast.expression.Field;
 import org.opensearch.sql.ast.expression.Function;
+import org.opensearch.sql.ast.expression.FunctionWithCachedValue;
 import org.opensearch.sql.ast.expression.HighlightFunction;
 import org.opensearch.sql.ast.expression.In;
 import org.opensearch.sql.ast.expression.Interval;
@@ -116,6 +117,10 @@ public T visitRelevanceFieldList(RelevanceFieldList node, C context) {
     return visitChildren(node, context);
   }
 
+  public T visitFunctionWithCachedValue(FunctionWithCachedValue node, C context) {
+    return visitChildren(node, context);
+  }
+
   public T visitUnresolvedAttribute(UnresolvedAttribute node, C context) {
     return visitChildren(node, context);
   }

core/src/main/java/org/opensearch/sql/ast/dsl/AstDSL.java

@@ -22,6 +22,7 @@
 import org.opensearch.sql.ast.expression.EqualTo;
 import org.opensearch.sql.ast.expression.Field;
 import org.opensearch.sql.ast.expression.Function;
+import org.opensearch.sql.ast.expression.FunctionWithCachedValue;
 import org.opensearch.sql.ast.expression.HighlightFunction;
 import org.opensearch.sql.ast.expression.In;
 import org.opensearch.sql.ast.expression.Interval;
@@ -229,6 +230,10 @@ public static Function function(String funcName, UnresolvedExpression... funcArg
     return new Function(funcName, Arrays.asList(funcArgs));
   }
 
+  public static Function functionLikeConstant(String funcName, UnresolvedExpression... funcArgs) {
+    return new FunctionWithCachedValue(funcName, Arrays.asList(funcArgs));
+  }
+
   /**
    * CASE
    *     WHEN search_condition THEN result_expr

core/src/main/java/org/opensearch/sql/ast/expression/FunctionWithCachedValue.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+
+package org.opensearch.sql.ast.expression;
+
+import java.util.List;
+import lombok.EqualsAndHashCode;
+import org.opensearch.sql.ast.AbstractNodeVisitor;
+
+/**
+ * Expression node that holds a function which should be replaced by its constant[1] value.
+ * [1] Constant at execution time.
+ */
+@EqualsAndHashCode(callSuper = false)
+public class FunctionWithCachedValue extends Function {
+
+  public FunctionWithCachedValue(String funcName, List<UnresolvedExpression> funcArgs) {
+    super(funcName, funcArgs);
+  }
+
+  @Override
+  public <R, C> R accept(AbstractNodeVisitor<R, C> nodeVisitor, C context) {
+    return nodeVisitor.visitFunctionWithCachedValue(this, context);
+  }
+}

core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java

@@ -28,10 +28,8 @@
 import java.time.format.TextStyle;
 import java.util.Locale;
 import java.util.concurrent.TimeUnit;
-import java.util.function.Supplier;
 import javax.annotation.Nullable;
 import lombok.experimental.UtilityClass;
-import org.opensearch.sql.common.utils.QueryContext;
 import org.opensearch.sql.data.model.ExprDateValue;
 import org.opensearch.sql.data.model.ExprDatetimeValue;
 import org.opensearch.sql.data.model.ExprIntegerValue;
@@ -104,15 +102,12 @@ public void register(BuiltinFunctionRepository repository) {
 
   /**
    * NOW() returns a constant time that indicates the time at which the statement began to execute.
+   * `fsp` argument support is removed until refactoring to avoid bug where `now()`, `now(x)` and
+   * `now(y) return different values.
    */
-  private LocalDateTime now(@Nullable Integer fsp) {
-    return formatLocalDateTime(QueryContext::getProcessingStartedTime, fsp);
-  }
-
   private FunctionResolver now(FunctionName functionName) {
     return define(functionName,
-        impl(() -> new ExprDatetimeValue(now((Integer)null)), DATETIME),
-        impl((v) -> new ExprDatetimeValue(now(v.integerValue())), DATETIME, INTEGER)
+        impl(() -> new ExprDatetimeValue(formatNow(null)), DATETIME)
     );
   }
 
@@ -135,21 +130,19 @@ private FunctionResolver localtime() {
   /**
    * SYSDATE() returns the time at which it executes.
    */
-  private LocalDateTime sysDate(@Nullable Integer fsp) {
-    return formatLocalDateTime(LocalDateTime::now, fsp);
-  }
-
   private FunctionResolver sysdate() {
     return define(BuiltinFunctionName.SYSDATE.getName(),
-        impl(() -> new ExprDatetimeValue(sysDate(null)), DATETIME),
-        impl((v) -> new ExprDatetimeValue(sysDate(v.integerValue())), DATETIME, INTEGER)
+        impl(() -> new ExprDatetimeValue(formatNow(null)), DATETIME),
+        impl((v) -> new ExprDatetimeValue(formatNow(v.integerValue())), DATETIME, INTEGER)
     );
   }
 
+  /**
+   * Synonym for @see `now`.
+   */
   private FunctionResolver curtime(FunctionName functionName) {
     return define(functionName,
-        impl(() -> new ExprTimeValue(sysDate(null).toLocalTime()), TIME),
-        impl((v) -> new ExprTimeValue(sysDate(v.integerValue()).toLocalTime()), TIME, INTEGER)
+        impl(() -> new ExprTimeValue(formatNow(null).toLocalTime()), TIME)
     );
   }
 
@@ -163,7 +156,7 @@ private FunctionResolver current_time() {
 
   private FunctionResolver curdate(FunctionName functionName) {
     return define(functionName,
-        impl(() -> new ExprDateValue(sysDate(null).toLocalDate()), DATE)
+        impl(() -> new ExprDateValue(formatNow(null).toLocalDate()), DATE)
     );
   }
 
@@ -829,15 +822,13 @@ private ExprValue exprYear(ExprValue date) {
   }
 
   /**
-   * Prepare LocalDateTime value.
-   * @param supplier A function which returns LocalDateTime to format.
+   * Prepare LocalDateTime value. Truncate fractional second part according to the argument.
    * @param fsp argument is given to specify a fractional seconds precision from 0 to 6,
    *            the return value includes a fractional seconds part of that many digits.
    * @return LocalDateTime object.
    */
-  private LocalDateTime formatLocalDateTime(Supplier<LocalDateTime> supplier,
-                                            @Nullable Integer fsp) {
-    var res = supplier.get();
+  private LocalDateTime formatNow(@Nullable Integer fsp) {
+    var res = LocalDateTime.now();
     if (fsp == null) {
       return res;
     }

core/src/test/java/org/opensearch/sql/analysis/ExpressionAnalyzerTest.java

@@ -8,7 +8,9 @@
 
 import static java.util.Collections.emptyList;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.opensearch.sql.ast.dsl.AstDSL.field;
 import static org.opensearch.sql.ast.dsl.AstDSL.function;
 import static org.opensearch.sql.ast.dsl.AstDSL.intLiteral;
@@ -26,6 +28,7 @@
 import com.google.common.collect.ImmutableMap;
 import java.util.Collections;
 import java.util.LinkedHashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Stream;
@@ -47,11 +50,13 @@
 import org.opensearch.sql.common.antlr.SyntaxCheckException;
 import org.opensearch.sql.data.model.ExprTupleValue;
 import org.opensearch.sql.data.model.ExprValueUtils;
+import org.opensearch.sql.data.type.ExprCoreType;
 import org.opensearch.sql.exception.SemanticCheckException;
 import org.opensearch.sql.expression.DSL;
 import org.opensearch.sql.expression.Expression;
 import org.opensearch.sql.expression.FunctionExpression;
 import org.opensearch.sql.expression.HighlightExpression;
+import org.opensearch.sql.expression.LiteralExpression;
 import org.opensearch.sql.expression.config.ExpressionConfig;
 import org.opensearch.sql.expression.window.aggregation.AggregateWindowFunction;
 import org.springframework.context.annotation.Configuration;
@@ -543,47 +548,45 @@ public void match_phrase_prefix_all_params() {
     );
   }
 
-  private static Stream<Arguments> functionNames() {
-    var dsl = new DSL(new ExpressionConfig().functionRepository());
-    return Stream.of(
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::now,
-            "now", true),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::current_timestamp,
-            "current_timestamp", true),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::localtimestamp,
-            "localtimestamp", true),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::localtime,
-            "localtime", true),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::sysdate,
-            "sysdate", true),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::curtime,
-            "curtime", true),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::current_time,
-            "current_time", true),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::curdate,
-            "curdate", false),
-        Arguments.of((Function<Expression[], FunctionExpression>)dsl::current_date,
-            "current_date", false));
-  }
-
-  @ParameterizedTest(name = "{1}")
-  @MethodSource("functionNames")
-  public void now_like_functions(Function<Expression[], FunctionExpression> function,
-                                 String name,
-                                 Boolean hasFsp) {
-    assertAnalyzeEqual(
-        function.apply(new Expression[]{}),
-        AstDSL.function(name));
-
-    if (hasFsp) {
-      assertAnalyzeEqual(
-          function.apply(new Expression[]{DSL.ref("integer_value", INTEGER)}),
-          AstDSL.function(name, field("integer_value")));
-
-      assertAnalyzeEqual(
-          function.apply(new Expression[]{DSL.literal(3)}),
-          AstDSL.function(name, intLiteral(3)));
-    }
+  @Test
+  public void functionLikeConstant_calculated_on_analyze() {
+    // Actually, we can call any function as functionLikeConstant to be calculated on analyze stage
+    assertTrue(analyze(AstDSL.functionLikeConstant("now")) instanceof LiteralExpression);
+    assertTrue(analyze(AstDSL.functionLikeConstant("localtime")) instanceof LiteralExpression);
+  }
+
+  @Test
+  public void function_isnt_calculated_on_analyze() {
+    assertTrue(analyze(function("now")) instanceof FunctionExpression);
+    assertTrue(analyze(AstDSL.function("localtime")) instanceof FunctionExpression);
+  }
+
+  @Test
+  public void functionLikeConstant_returns_constant_cached_value() {
+    var values = List.of(analyze(AstDSL.functionLikeConstant("now")),
+        analyze(AstDSL.functionLikeConstant("now")), analyze(AstDSL.functionLikeConstant("now")));
+    assertTrue(values.stream().allMatch(v ->
+        v.valueOf(null) == analyze(AstDSL.functionLikeConstant("now")).valueOf(null)));
+  }
+
+  @Test
+  public void function_returns_non_constant_value() {
+    // Even a function returns the same values - they are calculated on each call
+    // `sysdate()` which returns `LocalDateTime.now()` shouldn't be cached and should return always
+    // different values
+    var values = List.of(analyze(function("sysdate")), analyze(function("sysdate")),
+        analyze(function("sysdate")), analyze(function("sysdate")));
+    var referenceValue = analyze(function("sysdate")).valueOf(null);
+    assertTrue(values.stream().noneMatch(v -> v.valueOf(null) == referenceValue));
+  }
+
+  @Test
+  public void now_as_a_function_not_cached() {
+    // // We can call `now()` as a function, in that case nothing should be cached
+    var values = List.of(analyze(function("now")), analyze(function("now")),
+        analyze(function("now")), analyze(function("now")));
+    var referenceValue = analyze(function("now")).valueOf(null);
+    assertTrue(values.stream().noneMatch(v -> v.valueOf(null) == referenceValue));
   }
 
   @Test