Address issues flagged by checkstyle build step

core/src/main/java/org/opensearch/sql/executor/CanPaginateVisitor.java

@@ -5,17 +5,12 @@
 
 package org.opensearch.sql.executor;
 
+import java.util.concurrent.atomic.AtomicBoolean;
 import org.opensearch.sql.ast.AbstractNodeVisitor;
 import org.opensearch.sql.ast.Node;
 import org.opensearch.sql.ast.expression.AllFields;
-import org.opensearch.sql.ast.tree.Filter;
-import org.opensearch.sql.ast.tree.Limit;
 import org.opensearch.sql.ast.tree.Project;
 import org.opensearch.sql.ast.tree.Relation;
-import org.opensearch.sql.ast.tree.Sort;
-import org.opensearch.sql.ast.tree.Values;
-
-import java.util.concurrent.atomic.AtomicBoolean;
 
 /**
  * Use this unresolved plan visitor to check if a plan can be serialized by PaginatedPlanCache.

core/src/main/java/org/opensearch/sql/executor/PaginatedPlanCache.java

@@ -57,10 +57,15 @@ public Cursor convertToCursor(PhysicalPlan plan) {
     }
   }
 
+  /**
+   * Compress serialized query plan.
+   * @param str string representing a query plan
+   * @return str compressed with gzip.
+   */
   @SneakyThrows
   public static String compress(String str) {
     if (str == null || str.length() == 0) {
-        return null;
+      return null;
     }
 
     ByteArrayOutputStream out = new ByteArrayOutputStream();
@@ -70,10 +75,15 @@ public static String compress(String str) {
     return HashCode.fromBytes(out.toByteArray()).toString();
   }
 
+  /**
+   * Decompresses a query plan that was compress with {@link PaginatedPlanCache.compress}.
+   * @param input compressed query plan
+   * @return seria
+   */
   @SneakyThrows
   public static String decompress(String input) {
     if (input == null || input.length() == 0) {
-        return null;
+      return null;
     }
     GZIPInputStream gzip = new GZIPInputStream(new ByteArrayInputStream(
         HashCode.fromString(input).asBytes()));
@@ -114,10 +124,10 @@ public PhysicalPlan convertToPlan(String cursor) {
           throw new UnsupportedOperationException("Unsupported cursor");
         }
         cursor = cursor.substring(cursor.indexOf(',') + 1);
-        int currentPageIndex = Integer.parseInt(cursor, 0, cursor.indexOf(','), 10);
+        final int currentPageIndex = Integer.parseInt(cursor, 0, cursor.indexOf(','), 10);
 
         cursor = cursor.substring(cursor.indexOf(',') + 1);
-        int pageSize = Integer.parseInt(cursor, 0, cursor.indexOf(','), 10);
+        final int pageSize = Integer.parseInt(cursor, 0, cursor.indexOf(','), 10);
 
         cursor = cursor.substring(cursor.indexOf(',') + 1);
         if (!cursor.startsWith("(Project,")) {

core/src/main/java/org/opensearch/sql/planner/optimizer/rule/PushPageSize.java

@@ -17,8 +17,6 @@
 import org.opensearch.sql.planner.logical.LogicalRelation;
 import org.opensearch.sql.planner.optimizer.Rule;
 
-import java.util.Objects;
-
 public class PushPageSize
     implements Rule<LogicalPaginate> {
   /** Capture the table inside matched logical paginate operator. */

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/ContinueScrollRequest.java

@@ -5,6 +5,8 @@
 
 package org.opensearch.sql.opensearch.storage;
 
+import static org.opensearch.sql.opensearch.request.OpenSearchScrollRequest.DEFAULT_SCROLL_TIMEOUT;
+
 import java.util.function.Consumer;
 import java.util.function.Function;
 import lombok.EqualsAndHashCode;
@@ -18,8 +20,6 @@
 import org.opensearch.sql.opensearch.request.OpenSearchRequest;
 import org.opensearch.sql.opensearch.response.OpenSearchResponse;
 
-import static org.opensearch.sql.opensearch.request.OpenSearchScrollRequest.DEFAULT_SCROLL_TIMEOUT;
-
 public class ContinueScrollRequest implements OpenSearchRequest {
   final String initialScrollId;
 

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/OpenSearchPagedIndexScan.java

@@ -7,14 +7,11 @@
 
 import java.util.Collections;
 import java.util.Iterator;
-import java.util.List;
-
 import lombok.EqualsAndHashCode;
 import lombok.ToString;
 import org.opensearch.sql.data.model.ExprValue;
 import org.opensearch.sql.opensearch.client.OpenSearchClient;
 import org.opensearch.sql.opensearch.request.OpenSearchRequest;
-import org.opensearch.sql.opensearch.request.OpenSearchScrollRequest;
 import org.opensearch.sql.opensearch.response.OpenSearchResponse;
 import org.opensearch.sql.storage.TableScanOperator;
 

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/PagedRequestBuilder.java

@@ -10,5 +10,6 @@
 
 public interface PagedRequestBuilder {
   OpenSearchRequest build();
+
   OpenSearchRequest.IndexName getIndexName();
 }

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/SubsequentPageRequestBuilder.java

@@ -5,20 +5,15 @@
 
 package org.opensearch.sql.opensearch.storage;
 
+import lombok.RequiredArgsConstructor;
 import org.opensearch.sql.opensearch.data.value.OpenSearchExprValueFactory;
 import org.opensearch.sql.opensearch.request.OpenSearchRequest;
 
+@RequiredArgsConstructor
 public class SubsequentPageRequestBuilder implements PagedRequestBuilder {
-  private OpenSearchRequest.IndexName indexName;
+  final OpenSearchRequest.IndexName indexName;
   final String scrollId;
-  private OpenSearchExprValueFactory exprValueFactory;
-
-  public SubsequentPageRequestBuilder(OpenSearchRequest.IndexName indexName, String scanAsString,
-                                      OpenSearchExprValueFactory exprValueFactory) {
-    this.indexName = indexName;
-    scrollId = scanAsString;
-    this.exprValueFactory = exprValueFactory;
-  }
+  final OpenSearchExprValueFactory exprValueFactory;
 
   @Override
   public OpenSearchRequest build() {

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/scan/OpenSearchIndexScanAggregationBuilder.java

@@ -15,10 +15,10 @@
 import org.opensearch.sql.expression.NamedExpression;
 import org.opensearch.sql.expression.ReferenceExpression;
 import org.opensearch.sql.expression.aggregation.NamedAggregator;
+import org.opensearch.sql.expression.serialization.DefaultExpressionSerializer;
 import org.opensearch.sql.opensearch.response.agg.OpenSearchAggregationResponseParser;
 import org.opensearch.sql.opensearch.storage.OpenSearchIndexScan;
 import org.opensearch.sql.opensearch.storage.script.aggregation.AggregationQueryBuilder;
-import org.opensearch.sql.expression.serialization.DefaultExpressionSerializer;
 import org.opensearch.sql.planner.logical.LogicalAggregation;
 import org.opensearch.sql.planner.logical.LogicalSort;
 import org.opensearch.sql.storage.TableScanOperator;

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/scan/OpenSearchIndexScanQueryBuilder.java

@@ -20,10 +20,10 @@
 import org.opensearch.sql.expression.ExpressionNodeVisitor;
 import org.opensearch.sql.expression.NamedExpression;
 import org.opensearch.sql.expression.ReferenceExpression;
+import org.opensearch.sql.expression.serialization.DefaultExpressionSerializer;
 import org.opensearch.sql.opensearch.storage.OpenSearchIndexScan;
 import org.opensearch.sql.opensearch.storage.script.filter.FilterQueryBuilder;
 import org.opensearch.sql.opensearch.storage.script.sort.SortQueryBuilder;
-import org.opensearch.sql.expression.serialization.DefaultExpressionSerializer;
 import org.opensearch.sql.planner.logical.LogicalFilter;
 import org.opensearch.sql.planner.logical.LogicalHighlight;
 import org.opensearch.sql.planner.logical.LogicalLimit;

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/script/ExpressionScriptEngine.java

@@ -16,9 +16,9 @@
 import org.opensearch.script.ScriptContext;
 import org.opensearch.script.ScriptEngine;
 import org.opensearch.sql.expression.Expression;
+import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 import org.opensearch.sql.opensearch.storage.script.aggregation.ExpressionAggregationScriptFactory;
 import org.opensearch.sql.opensearch.storage.script.filter.ExpressionFilterScriptFactory;
-import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 
 /**
  * Custom expression script engine that supports using core engine expression code in DSL

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/script/aggregation/AggregationQueryBuilder.java

@@ -30,13 +30,13 @@
 import org.opensearch.sql.expression.NamedExpression;
 import org.opensearch.sql.expression.ReferenceExpression;
 import org.opensearch.sql.expression.aggregation.NamedAggregator;
+import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 import org.opensearch.sql.opensearch.response.agg.CompositeAggregationParser;
 import org.opensearch.sql.opensearch.response.agg.MetricParser;
 import org.opensearch.sql.opensearch.response.agg.NoBucketAggregationParser;
 import org.opensearch.sql.opensearch.response.agg.OpenSearchAggregationResponseParser;
 import org.opensearch.sql.opensearch.storage.script.aggregation.dsl.BucketAggregationBuilder;
 import org.opensearch.sql.opensearch.storage.script.aggregation.dsl.MetricAggregationBuilder;
-import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 
 /**
  * Build the AggregationBuilder from the list of {@link NamedAggregator}

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/script/aggregation/dsl/AggregationBuilderHelper.java

@@ -17,8 +17,8 @@
 import org.opensearch.sql.expression.FunctionExpression;
 import org.opensearch.sql.expression.LiteralExpression;
 import org.opensearch.sql.expression.ReferenceExpression;
-import org.opensearch.sql.opensearch.storage.script.ScriptUtils;
 import org.opensearch.sql.expression.serialization.ExpressionSerializer;
+import org.opensearch.sql.opensearch.storage.script.ScriptUtils;
 
 /**
  * Abstract Aggregation Builder.

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/script/aggregation/dsl/BucketAggregationBuilder.java

@@ -17,8 +17,8 @@
 import org.opensearch.search.sort.SortOrder;
 import org.opensearch.sql.ast.expression.SpanUnit;
 import org.opensearch.sql.expression.NamedExpression;
-import org.opensearch.sql.expression.span.SpanExpression;
 import org.opensearch.sql.expression.serialization.ExpressionSerializer;
+import org.opensearch.sql.expression.span.SpanExpression;
 
 /**
  * Bucket Aggregation Builder.

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/script/aggregation/dsl/MetricAggregationBuilder.java

@@ -25,13 +25,13 @@
 import org.opensearch.sql.expression.LiteralExpression;
 import org.opensearch.sql.expression.ReferenceExpression;
 import org.opensearch.sql.expression.aggregation.NamedAggregator;
+import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 import org.opensearch.sql.opensearch.response.agg.FilterParser;
 import org.opensearch.sql.opensearch.response.agg.MetricParser;
 import org.opensearch.sql.opensearch.response.agg.SingleValueParser;
 import org.opensearch.sql.opensearch.response.agg.StatsParser;
 import org.opensearch.sql.opensearch.response.agg.TopHitsParser;
 import org.opensearch.sql.opensearch.storage.script.filter.FilterQueryBuilder;
-import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 
 /**
  * Build the Metric Aggregation and List of {@link MetricParser} from {@link NamedAggregator}.

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/script/filter/FilterQueryBuilder.java

@@ -24,6 +24,7 @@
 import org.opensearch.sql.expression.FunctionExpression;
 import org.opensearch.sql.expression.function.BuiltinFunctionName;
 import org.opensearch.sql.expression.function.FunctionName;
+import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 import org.opensearch.sql.opensearch.storage.script.filter.lucene.LikeQuery;
 import org.opensearch.sql.opensearch.storage.script.filter.lucene.LuceneQuery;
 import org.opensearch.sql.opensearch.storage.script.filter.lucene.RangeQuery;
@@ -38,7 +39,6 @@
 import org.opensearch.sql.opensearch.storage.script.filter.lucene.relevance.QueryStringQuery;
 import org.opensearch.sql.opensearch.storage.script.filter.lucene.relevance.SimpleQueryStringQuery;
 import org.opensearch.sql.opensearch.storage.script.filter.lucene.relevance.WildcardQuery;
-import org.opensearch.sql.expression.serialization.ExpressionSerializer;
 
 @RequiredArgsConstructor
 public class FilterQueryBuilder extends ExpressionNodeVisitor<QueryBuilder, Object> {

plugin/src/main/java/org/opensearch/sql/plugin/SQLPlugin.java

@@ -57,6 +57,7 @@
 import org.opensearch.sql.datasource.DataSourceServiceImpl;
 import org.opensearch.sql.datasource.model.DataSource;
 import org.opensearch.sql.datasource.model.DataSourceMetadata;
+import org.opensearch.sql.expression.serialization.DefaultExpressionSerializer;
 import org.opensearch.sql.legacy.esdomain.LocalClusterState;
 import org.opensearch.sql.legacy.executor.AsyncRestExecutor;
 import org.opensearch.sql.legacy.metrics.Metrics;
@@ -68,7 +69,6 @@
 import org.opensearch.sql.opensearch.setting.OpenSearchSettings;
 import org.opensearch.sql.opensearch.storage.OpenSearchDataSourceFactory;
 import org.opensearch.sql.opensearch.storage.script.ExpressionScriptEngine;
-import org.opensearch.sql.expression.serialization.DefaultExpressionSerializer;
 import org.opensearch.sql.plugin.config.OpenSearchPluginModule;
 import org.opensearch.sql.plugin.datasource.DataSourceSettings;
 import org.opensearch.sql.plugin.rest.RestPPLQueryAction;

sql/src/main/java/org/opensearch/sql/sql/domain/SQLQueryRequest.java

@@ -65,19 +65,20 @@ public class SQLQueryRequest {
   private boolean sanitize = true;
 
   private String cursor = "";
+
   /**
    * Constructor of SQLQueryRequest that passes request params.
    */
-  public SQLQueryRequest(
-      JSONObject jsonContent, String query, String path, Map<String, String> params, String cursor) {
+  public SQLQueryRequest(JSONObject jsonContent, String query, String path,
+                         Map<String, String> params, String cursor) {
     this.jsonContent = jsonContent;
     this.query = query;
     this.path = path;
     this.params = params;
     this.format = getFormat(params);
     this.sanitize = shouldSanitize(params);
     // TODO hack
-    this.cursor = cursor == null? "" : cursor;
+    this.cursor = cursor == null ? "" : cursor;
   }
 
   /**