Add REGEXP_REPLACE function.

docs/querying/math-expr.md

@@ -84,6 +84,7 @@ The following built-in functions are available.
 |parse_long|parse_long(string[, radix]) parses a string as a long with the given radix, or 10 (decimal) if a radix is not provided.|
 |regexp_extract|regexp_extract(expr, pattern[, index]) applies a regular expression pattern and extracts a capture group index, or null if there is no match. If index is unspecified or zero, returns the substring that matched the pattern. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern.|
 |regexp_like|regexp_like(expr, pattern) returns whether `expr` matches regular expression `pattern`. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern. |
+|regexp_replace|regexp_replace(expr, pattern, replacement) replaces all instances of a regular expression pattern with a given replacement string. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern.|
 |contains_string|contains_string(expr, string) returns whether `expr` contains `string` as a substring. This method is case-sensitive.|
 |icontains_string|contains_string(expr, string) returns whether `expr` contains `string` as a substring. This method is case-insensitive.|
 |replace|replace(expr, pattern, replacement) replaces pattern with replacement|

docs/querying/sql-functions.md

@@ -1141,6 +1141,15 @@ Applies a regular expression to the string expression and returns the _n_th matc
 
 Returns true or false signifying whether the regular expression finds a match in the string expression.
 
+## REGEXP_REPLACE
+
+`REGEXP_REPLACE(<CHARACTER>, <CHARACTER>, <CHARACTER>)`
+
+**Function type:** [Scalar, string](sql-scalar.md#string-functions)
+
+Replaces all occurrences of a regular expression in a string expression with a replacement string. The replacement
+string may refer to capture groups using `$1`, `$2`, etc.
+
 ## REPEAT
 
 `REPEAT(<CHARACTER>, [<INTEGER>])`

docs/querying/sql-scalar.md

@@ -103,6 +103,7 @@ String functions accept strings, and return a type appropriate to the function.
 |`POSITION(needle IN haystack [FROM fromIndex])`|Returns the index of `needle` within `haystack`, with indexes starting from 1. The search will begin at `fromIndex`, or 1 if `fromIndex` is not specified. If `needle` is not found, returns 0.|
 |`REGEXP_EXTRACT(expr, pattern, [index])`|Apply regular expression `pattern` to `expr` and extract a capture group, or `NULL` if there is no match. If index is unspecified or zero, returns the first substring that matched the pattern. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern. Note: when `druid.generic.useDefaultValueForNull = true`, it is not possible to differentiate an empty-string match from a non-match (both will return `NULL`).|
 |`REGEXP_LIKE(expr, pattern)`|Returns whether `expr` matches regular expression `pattern`. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern. Similar to [`LIKE`](sql-operators.md#logical-operators), but uses regexps instead of LIKE patterns. Especially useful in WHERE clauses.|
+|`REGEXP_REPLACE(expr, pattern, replacement)`|Replaces all occurrences of regular expression `pattern` within `expr` with `replacement`. The replacement string may refer to capture groups using `$1`, `$2`, etc. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern.|
 |`CONTAINS_STRING(expr, str)`|Returns true if the `str` is a substring of `expr`.|
 |`ICONTAINS_STRING(expr, str)`|Returns true if the `str` is a substring of `expr`. The match is case-insensitive.|
 |`REPLACE(expr, pattern, replacement)`|Replaces pattern with replacement in `expr`, and returns the result.|

processing/src/main/java/org/apache/druid/query/expression/RegexpReplaceExprMacro.java

@@ -0,0 +1,157 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.query.expression;
+
+import org.apache.druid.common.config.NullHandling;
+import org.apache.druid.math.expr.Expr;
+import org.apache.druid.math.expr.ExprEval;
+import org.apache.druid.math.expr.ExprMacroTable;
+import org.apache.druid.math.expr.ExpressionType;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class RegexpReplaceExprMacro implements ExprMacroTable.ExprMacro
+{
+  private static final String FN_NAME = "regexp_replace";
+
+  @Override
+  public String name()
+  {
+    return FN_NAME;
+  }
+
+  @Override
+  public Expr apply(final List<Expr> args)
+  {
+    validationHelperCheckArgumentCount(args, 3);
+
+    if (args.stream().skip(1).allMatch(Expr::isLiteral)) {
+      return new RegexpReplaceExpr(args);
+    } else {
+      return new RegexpReplaceDynamicExpr(args);
+    }
+  }
+
+  abstract class BaseRegexpReplaceExpr extends ExprMacroTable.BaseScalarMacroFunctionExpr
+  {
+    public BaseRegexpReplaceExpr(final List<Expr> args)
+    {
+      super(FN_NAME, args);
+    }
+
+    @Nullable
+    @Override
+    public ExpressionType getOutputType(InputBindingInspector inspector)
+    {
+      return ExpressionType.STRING;
+    }
+
+    @Override
+    public Expr visit(Shuttle shuttle)
+    {
+      return shuttle.visit(apply(shuttle.visitAll(args)));
+    }
+  }
+
+  /**
+   * Expr when pattern and replacement are literals.
+   */
+  class RegexpReplaceExpr extends BaseRegexpReplaceExpr
+  {
+    private final Expr arg;
+    private final Pattern pattern;
+    private final String replacement;
+
+    private RegexpReplaceExpr(List<Expr> args)
+    {
+      super(args);
+
+      final Expr patternExpr = args.get(1);
+      final Expr replacementExpr = args.get(2);
+
+      if (!ExprUtils.isStringLiteral(patternExpr)
+          && !(patternExpr.isLiteral() && patternExpr.getLiteralValue() == null)) {
+        throw validationFailed("pattern must be a string literal");
+      }
+
+      if (!ExprUtils.isStringLiteral(replacementExpr)
+          && !(replacementExpr.isLiteral() && replacementExpr.getLiteralValue() == null)) {
+        throw validationFailed("replacement must be a string literal");
+      }
+
+      final String patternString = NullHandling.nullToEmptyIfNeeded((String) patternExpr.getLiteralValue());
+
+      this.arg = args.get(0);
+      this.pattern = patternString != null ? Pattern.compile(patternString) : null;
+      this.replacement = NullHandling.nullToEmptyIfNeeded((String) replacementExpr.getLiteralValue());
+    }
+
+    @Nonnull
+    @Override
+    public ExprEval<?> eval(final ObjectBinding bindings)
+    {
+      if (pattern == null || replacement == null) {
+        return ExprEval.of(null);
+      }
+
+      final String s = NullHandling.nullToEmptyIfNeeded(arg.eval(bindings).asString());
+
+      if (s == null) {
+        return ExprEval.of(null);
+      } else {
+        final Matcher matcher = pattern.matcher(s);
+        final String retVal = matcher.replaceAll(replacement);
+        return ExprEval.of(retVal);
+      }
+    }
+  }
+
+  /**
+   * Expr when pattern and replacement are dynamic (not literals).
+   */
+  class RegexpReplaceDynamicExpr extends BaseRegexpReplaceExpr
+  {
+    private RegexpReplaceDynamicExpr(List<Expr> args)
+    {
+      super(args);
+    }
+
+    @Nonnull
+    @Override
+    public ExprEval<?> eval(final ObjectBinding bindings)
+    {
+      final String s = NullHandling.nullToEmptyIfNeeded(args.get(0).eval(bindings).asString());
+      final String pattern = NullHandling.nullToEmptyIfNeeded(args.get(1).eval(bindings).asString());
+      final String replacement = NullHandling.nullToEmptyIfNeeded(args.get(2).eval(bindings).asString());
+
+      if (s == null || pattern == null || replacement == null) {
+        return ExprEval.of(null);
+      } else {
+        final Matcher matcher = Pattern.compile(pattern).matcher(s);
+        final String retVal = matcher.replaceAll(replacement);
+        return ExprEval.of(retVal);
+      }
+    }
+  }
+}