ahkcs
diff --git a/‎core/src/main/java/org/opensearch/sql/analysis/Analyzer.java‎
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diff --git a/‎core/src/main/java/org/opensearch/sql/ast/AbstractNodeVisitor.java‎
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diff --git a/‎core/src/main/java/org/opensearch/sql/ast/analysis/FieldResolutionVisitor.java‎
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diff --git a/‎core/src/main/java/org/opensearch/sql/ast/expression/Let.java‎
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diff --git a/‎core/src/main/java/org/opensearch/sql/calcite/CalciteRexNodeVisitor.java‎
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diff --git a/‎docs/category.json‎
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diff --git a/‎docs/user/ppl/cmd/fieldformat.md‎
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diff --git a/‎integ-test/src/test/java/org/opensearch/sql/calcite/CalciteNoPushdownIT.java‎
Lines changed: 1 addition & 0 deletions b/‎integ-test/src/test/java/org/opensearch/sql/calcite/CalciteNoPushdownIT.java‎
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diff --git a/‎integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteExplainIT.java‎
Lines changed: 16 additions & 0 deletions b/‎integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteExplainIT.java‎
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diff --git a/‎integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteFieldFormatCommandIT.java‎
Lines changed: 122 additions & 0 deletions b/‎integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteFieldFormatCommandIT.java‎
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@@ -526,6 +526,12 @@ public LogicalPlan visitEval(Eval node, AnalysisContext context) {
     return new LogicalEval(child, expressionsBuilder.build());
   }
 
+  /** Build {@link LogicalEval}. */
+  @Override
+  public LogicalPlan visitFieldFormat(Eval node, AnalysisContext context) {
+    throw getOnlyForCalciteException("fieldformat");
+  }
+
   @Override
   public LogicalPlan visitAddTotals(AddTotals node, AnalysisContext context) {
     throw getOnlyForCalciteException("addtotals");
 
@@ -264,6 +264,10 @@ public T visitEval(Eval node, C context) {
     return visitChildren(node, context);
   }
 
+  public T visitFieldFormat(Eval node, C context) {
+    return visitChildren(node, context);
+  }
+
   public T visitParse(Parse node, C context) {
     return visitChildren(node, context);
   }
 
@@ -626,6 +626,12 @@ public Node visitAddColTotals(AddColTotals node, FieldResolutionContext context)
     return node;
   }
 
+  @Override
+  public Node visitFieldFormat(Eval node, FieldResolutionContext context) {
+    visitChildren(node, context);
+    return node;
+  }
+
   @Override
   public Node visitExpand(Expand node, FieldResolutionContext context) {
     Set<String> expandFields = extractFieldsFromExpression(node.getField());
 
@@ -20,6 +20,8 @@
 public class Let extends UnresolvedExpression {
   private final Field var;
   private final UnresolvedExpression expression;
+  private final Literal concatPrefix;
+  private final Literal concatSuffix;
 
   public Let(Field var, UnresolvedExpression expression) {
     String varName = var.getField().toString();
@@ -29,6 +31,21 @@ public Let(Field var, UnresolvedExpression expression) {
     }
     this.var = var;
     this.expression = expression;
+    this.concatPrefix = null;
+    this.concatSuffix = null;
+  }
+
+  public Let(
+      Field var, UnresolvedExpression expression, Literal concatPrefix, Literal concatSuffix) {
+    String varName = var.getField().toString();
+    if (OpenSearchConstants.METADATAFIELD_TYPE_MAP.containsKey(varName)) {
+      throw new IllegalArgumentException(
+          String.format("Cannot use metadata field [%s] as the eval field.", varName));
+    }
+    this.var = var;
+    this.expression = expression;
+    this.concatPrefix = concatPrefix;
+    this.concatSuffix = concatSuffix;
   }
 
   @Override
 
@@ -398,6 +398,28 @@ public RexNode visitLambdaFunction(LambdaFunction node, CalcitePlanContext conte
   @Override
   public RexNode visitLet(Let node, CalcitePlanContext context) {
     RexNode expr = analyze(node.getExpression(), context);
+    if (node.getConcatPrefix() != null) {
+
+      expr =
+          context.rexBuilder.makeCall(
+              SqlStdOperatorTable.CONCAT,
+              context.rexBuilder.makeLiteral(
+                  node.getConcatPrefix().getValue(),
+                  context.rexBuilder.getTypeFactory().createSqlType(SqlTypeName.VARCHAR),
+                  true),
+              expr);
+    }
+    if (node.getConcatSuffix() != null) {
+
+      expr =
+          context.rexBuilder.makeCall(
+              SqlStdOperatorTable.CONCAT,
+              expr,
+              context.rexBuilder.makeLiteral(
+                  node.getConcatSuffix().getValue(),
+                  context.rexBuilder.getTypeFactory().createSqlType(SqlTypeName.VARCHAR),
+                  true));
+    }
     return context.relBuilder.alias(expr, node.getVar().getField().toString());
   }
 
 
@@ -17,6 +17,7 @@
     "user/ppl/cmd/describe.md",
     "user/ppl/cmd/eventstats.md",
     "user/ppl/cmd/eval.md",
+    "user/ppl/cmd/fieldformat.md",
     "user/ppl/cmd/fields.md",
     "user/ppl/cmd/fillnull.md",
     "user/ppl/cmd/grok.md",
 
@@ -0,0 +1,128 @@
+
+# fieldformat
+
+The `fieldformat` command sets the value to a field with the specified expression and appends the field with evaluated result to the search results. The command is an alias of eval command.
+Additionally, it also provides string concatenation dot operator followed by and/or follows a string that will be concatenated to the expression.
+
+
+## Syntax
+
+The `fieldformat` command has the following syntax:
+
+```syntax
+ fieldformat <field>=[(prefix).]<expression>[.(suffix)] ["," <field>=[(prefix).]<expression>[.(suffix)] ]...
+
+```
+
+## Parameters
+
+The `fieldformat` command supports the following parameters.
+
+| Parameter| Required/Optional | Description                                                                                                                                   |
+|----------------|-------------------|-----------------------------------------------------------------------------------------------------------------------------------------------|
+| `<field>`      | Required          | The name of the field to create or update. If the field does not exist, a new field is added. If it already exists, its value is overwritten. |
+| `<expression>` | Required          | The expression to evaluate.  The expression can have a prefix and/or suffix string part that will be concatenated to the expression.          |
+| `prefix`       | Optional          | A string before the expression followed by dot operator which will be concatenated as prefix to the evaluated expression value.               |
+| `suffix`       | Optional          | A string that follows  the expression and dot operator which will be concatenated as suffix to the evaluated expression value.                |
+  
+
+## Example 1: Create a new field  
+
+The following query creates a new `doubleAge` field for each document:
+  
+```ppl
+source=accounts
+| fieldformat doubleAge = age * 2
+| fields age, doubleAge
+```
+  
+The query returns the following results:
+  
+```text
+fetched rows / total rows = 4/4
++-----+-----------+
+| age | doubleAge |
+|-----+-----------|
+| 32  | 64        |
+| 36  | 72        |
+| 28  | 56        |
+| 33  | 66        |
++-----+-----------+
+```
+  
+
+## Example 2: Override an existing field  
+
+The following query overrides the `age` field by adding `1` to its value:
+  
+```ppl
+source=accounts
+| fieldformat age = age + 1
+| fields age
+```
+  
+The query returns the following results:
+  
+```text
+fetched rows / total rows = 4/4
++-----+
+| age |
+|-----|
+| 33  |
+| 37  |
+| 29  |
+| 34  |
++-----+
+```
+  
+
+  
+
+## Example 3: String concatenation with prefix 
+
+The following query uses the `.` (dot) operator for string concatenation. You can concatenate string literals and field values as follows:
+  
+```ppl
+source=accounts 
+| fieldformat greeting = 'Hello '.tostring( firstname) 
+| fields firstname, greeting
+```
+  
+The query returns the following results:
+  
+```text
+fetched rows / total rows = 4/4
++-----------+---------------+
+| firstname | greeting      |
+|-----------+---------------|
+| Amber     | Hello Amber   |
+| Hattie    | Hello Hattie  |
+| Nanette   | Hello Nanette |
+| Dale      | Hello Dale    |
++-----------+---------------+
+```
+  
+
+## Example 4: String concatenation with dot operator, prefix and suffix
+
+The following query performs prefix and suffix string concatenation operations using dot operator:
+
+```ppl
+source=accounts | fieldformat age_info =  'Age: '.CAST(age AS STRING).' years.' | fields firstname, age, age_info
+```
+
+The query returns the following results:
+
+```text
+fetched rows / total rows = 4/4
++-----------+-----+----------------+
+| firstname | age | age_info       |
+|-----------+-----+----------------|
+| Amber     | 32  | Age: 32 years. |
+| Hattie    | 36  | Age: 36 years. |
+| Nanette   | 28  | Age: 28 years. |
+| Dale      | 33  | Age: 33 years. |
++-----------+-----+----------------+
+```
+
+
@@ -34,6 +34,7 @@
   CalciteDedupCommandIT.class,
   CalciteDescribeCommandIT.class,
   CalciteExpandCommandIT.class,
+  CalciteFieldFormatCommandIT.class,
   CalciteFieldsCommandIT.class,
   CalciteFillNullCommandIT.class,
   CalciteFlattenCommandIT.class,
 
@@ -26,6 +26,7 @@
 
 import java.io.IOException;
 import java.util.Locale;
+import org.apache.commons.text.StringEscapeUtils;
 import org.junit.Assert;
 import org.junit.Ignore;
 import org.junit.Test;
@@ -2516,6 +2517,21 @@ public void testAggFilterOnNestedFields() throws IOException {
                 TEST_INDEX_CASCADED_NESTED)));
   }
 
+  @Test
+  public void testFieldFormatExplain() throws Exception {
+
+    enabledOnlyWhenPushdownIsEnabled();
+    String expected = loadExpectedPlan("explain_field_format.yaml");
+    assertYamlEqualsIgnoreId(
+        expected,
+        explainQueryYaml(
+            StringEscapeUtils.escapeJson(
+                StringUtils.format(
+                    "source=%s | head 5| fieldformat formatted_balance ="
+                        + " \"$\".tostring(balance,\"commas\") ",
+                    TEST_INDEX_ACCOUNT))));
+  }
+
   @Test
   public void testExplainMvCombine() throws IOException {
     String query =
 
@@ -0,0 +1,122 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.calcite.remote;
+
+import static org.opensearch.sql.util.MatcherUtils.*;
+
+import java.io.IOException;
+import org.apache.commons.text.StringEscapeUtils;
+import org.json.JSONObject;
+import org.junit.jupiter.api.Test;
+import org.opensearch.client.Request;
+import org.opensearch.sql.ppl.PPLIntegTestCase;
+
+public class CalciteFieldFormatCommandIT extends PPLIntegTestCase {
+
+  @Override
+  public void init() throws Exception {
+    super.init();
+    enableCalcite();
+
+    loadIndex(Index.BANK);
+
+    // Create test data for string concatenation
+    Request request1 = new Request("PUT", "/test_eval/_doc/1?refresh=true");
+    request1.setJsonEntity("{\"name\": \"Alice\", \"age\": 25, \"title\": \"Engineer\"}");
+    client().performRequest(request1);
+
+    Request request2 = new Request("PUT", "/test_eval/_doc/2?refresh=true");
+    request2.setJsonEntity("{\"name\": \"Bob\", \"age\": 30, \"title\": \"Manager\"}");
+    client().performRequest(request2);
+
+    Request request3 = new Request("PUT", "/test_eval/_doc/3?refresh=true");
+    request3.setJsonEntity("{\"name\": \"Charlie\", \"age\": null, \"title\": \"Analyst\"}");
+    client().performRequest(request3);
+  }
+
+  @Test
+  public void testFieldFormatStringConcatenation() throws IOException {
+    JSONObject result =
+        executeQuery(
+            StringEscapeUtils.escapeJson(
+                "source=test_eval | fieldformat greeting = 'Hello ' + name"));
+    verifySchema(
+        result,
+        schema("name", "string"),
+        schema("title", "string"),
+        schema("age", "bigint"),
+        schema("greeting", "string"));
+    verifyDataRows(
+        result,
+        rows("Alice", "Engineer", 25, "Hello Alice"),
+        rows("Bob", "Manager", 30, "Hello Bob"),
+        rows("Charlie", "Analyst", null, "Hello Charlie"));
+  }
+
+  @Test
+  public void testFieldFormatStringConcatenationWithNullFieldToString() throws IOException {
+    JSONObject result =
+        executeQuery(
+            StringEscapeUtils.escapeJson(
+                "source=test_eval | fieldformat age_desc = \"Age: \".tostring(age,\"commas\") |"
+                    + " fields name, age, age_desc"));
+    verifySchema(
+        result, schema("name", "string"), schema("age", "bigint"), schema("age_desc", "string"));
+    verifyDataRows(
+        result,
+        rows("Alice", 25, "Age: 25"),
+        rows("Bob", 30, "Age: 30"),
+        rows("Charlie", null, null));
+  }
+
+  @Test
+  public void testFieldFormatStringConcatenationWithNullField() throws IOException {
+    JSONObject result =
+        executeQuery(
+            StringEscapeUtils.escapeJson(
+                "source=test_eval | fieldformat age_desc = \"Age: \".CAST(age AS STRING) | fields"
+                    + " name, age, age_desc"));
+    verifySchema(
+        result, schema("name", "string"), schema("age", "bigint"), schema("age_desc", "string"));
+    verifyDataRows(
+        result,
+        rows("Alice", 25, "Age: 25"),
+        rows("Bob", 30, "Age: 30"),
+        rows("Charlie", null, null));
+  }
+
+  @Test
+  public void testFieldFormatStringConcatWithSuffix() throws IOException {
+    JSONObject result =
+        executeQuery(
+            StringEscapeUtils.escapeJson(
+                "source=test_eval | fieldformat age_desc = CAST(age AS STRING).\" years\" | fields"
+                    + " name, age, age_desc"));
+    verifySchema(
+        result, schema("name", "string"), schema("age", "bigint"), schema("age_desc", "string"));
+    verifyDataRows(
+        result,
+        rows("Alice", 25, "25 years"),
+        rows("Bob", 30, "30 years"),
+        rows("Charlie", null, null));
+  }
+
+  @Test
+  public void testFieldFormatStringConcatWithPrefixSuffix() throws IOException {
+    JSONObject result =
+        executeQuery(
+            StringEscapeUtils.escapeJson(
+                "source=test_eval | fieldformat age_desc = \"Age: \".CAST(age AS STRING).\" years\""
+                    + " | fields name, age, age_desc"));
+    verifySchema(
+        result, schema("name", "string"), schema("age", "bigint"), schema("age_desc", "string"));
+    verifyDataRows(
+        result,
+        rows("Alice", 25, "Age: 25 years"),
+        rows("Bob", 30, "Age: 30 years"),
+        rows("Charlie", null, null));
+  }
+}
Original file line number	Diff line number	Diff line change
`@@ -264,6 +264,10 @@ public T visitEval(Eval node, C context) {`
`264`	`264`	`return visitChildren(node, context);`
`265`	`265`	`}`
`266`	`266`
	`267`	`+ public T visitFieldFormat(Eval node, C context) {`
	`268`	`+ return visitChildren(node, context);`
	`269`	`+ }`
	`270`	`+`
`267`	`271`	`public T visitParse(Parse node, C context) {`
`268`	`272`	`return visitChildren(node, context);`
`269`	`273`	`}`