Add ES|QL helpers (#762) (#763)

Adds helpers for ES|QL.

The ES|QL result format is meant to be compact: it is composed of a metadata part giving field names and their types and a 2D array of values, which isn't easy to use in application code.

This PR provides adapters that convert the ES|QL JSON result format into higher level types that are easier to use. Two adapters are provided:
* An `ObjectsAdatper` that combines field names and values from the array to build a collection of objects using JSON to object mapping
* A `ResultSetAdpater` that provides an implementation of the well-known JDBC `ResultSet`. This is a cursor-based API where the application can inspect at runtime the type and names of the ES|QL results, and is therefore more suited for ad-hoc or dynamic queries where the result structure isn't known in advance.

Along with adapters, additional methods in `ElasticsearchEsqlClient` provide simple way to send queries using just a string and optional parameters when you don't need to specify additional request details.

Co-authored-by: Sylvain Wallez <sylvain@elastic.co>

java-client/src/main-flavored/java/co/elastic/clients/elasticsearch/_helpers/esql/EsqlAdapter.java

@@ -0,0 +1,47 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. 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 co.elastic.clients.elasticsearch._helpers.esql;
+
+import co.elastic.clients.ApiClient;
+import co.elastic.clients.elasticsearch.esql.QueryRequest;
+import co.elastic.clients.transport.ElasticsearchTransport;
+import co.elastic.clients.transport.endpoints.BinaryResponse;
+
+import java.io.IOException;
+
+/**
+ * A deserializer for ES|QL responses.
+ */
+public interface EsqlAdapter<Result> {
+    /**
+     * ESQL result format this deserializer accepts (text, csv, json, arrow, etc.)
+     */
+    String format();
+
+    /**
+     * For JSON results, whether the result should be organized in rows or columns
+     */
+    boolean columnar();
+
+    /**
+     * Deserialize the raw http response returned by the server
+     */
+    Result deserialize(ApiClient<ElasticsearchTransport, ?> client, QueryRequest request, BinaryResponse response) throws IOException;
+}

java-client/src/main-flavored/java/co/elastic/clients/elasticsearch/_helpers/esql/EsqlAdapterBase.java

@@ -0,0 +1,69 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. 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 co.elastic.clients.elasticsearch._helpers.esql;
+
+import co.elastic.clients.json.JsonpDeserializer;
+import co.elastic.clients.json.JsonpMapper;
+import co.elastic.clients.json.JsonpMappingException;
+import co.elastic.clients.json.JsonpUtils;
+import jakarta.json.stream.JsonParser;
+
+import java.util.List;
+
+public abstract class EsqlAdapterBase<T> implements EsqlAdapter<T> {
+
+    /**
+     * Reads the header of an ES|QL response, moving the parser at the beginning of the first value row.
+     * The caller can then read row arrays until finding an end array that closes the top-level array.
+     */
+    public static EsqlMetadata readHeader(JsonParser parser, JsonpMapper mapper) {
+        JsonpUtils.expectNextEvent(parser, JsonParser.Event.START_OBJECT);
+        JsonpUtils.expectNextEvent(parser, JsonParser.Event.KEY_NAME);
+
+        if (!"columns".equals(parser.getString())) {
+            throw new JsonpMappingException("Expecting a 'columns' property, but found '" + parser.getString() + "'", parser.getLocation());
+        }
+
+        List<EsqlMetadata.EsqlColumn> columns = JsonpDeserializer
+            .arrayDeserializer(EsqlMetadata.EsqlColumn._DESERIALIZER)
+            .deserialize(parser, mapper);
+
+        EsqlMetadata result = new EsqlMetadata();
+        result.columns = columns;
+
+        JsonpUtils.expectNextEvent(parser, JsonParser.Event.KEY_NAME);
+
+        if (!"values".equals(parser.getString())) {
+            throw new JsonpMappingException("Expecting a 'values' property, but found '" + parser.getString() + "'", parser.getLocation());
+        }
+
+        JsonpUtils.expectNextEvent(parser, JsonParser.Event.START_ARRAY);
+
+        return result;
+    }
+
+    /**
+     * Checks the footer of an ES|QL response, once the values have been read.
+     */
+    public static void readFooter(JsonParser parser) {
+        JsonpUtils.expectNextEvent(parser, JsonParser.Event.END_OBJECT);
+    }
+
+}

java-client/src/main-flavored/java/co/elastic/clients/elasticsearch/_helpers/esql/EsqlHelper.java

@@ -0,0 +1,114 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. 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 co.elastic.clients.elasticsearch._helpers.esql;
+
+import co.elastic.clients.elasticsearch._types.FieldValue;
+import co.elastic.clients.elasticsearch.esql.ElasticsearchEsqlAsyncClient;
+import co.elastic.clients.elasticsearch.esql.ElasticsearchEsqlClient;
+import co.elastic.clients.elasticsearch.esql.QueryRequest;
+import co.elastic.clients.json.JsonData;
+import co.elastic.clients.transport.endpoints.BinaryResponse;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+
+public class EsqlHelper {
+
+    //----- Synchronous
+
+    public static <T> T query(
+        ElasticsearchEsqlClient client, EsqlAdapter<T> adapter, String query, Object... params
+    ) throws IOException {
+        QueryRequest request = buildRequest(adapter, query, params);
+        BinaryResponse response = client.query(request);
+        return adapter.deserialize(client, request, response);
+    }
+
+    public static <T> T query(ElasticsearchEsqlClient client, EsqlAdapter<T> adapter, QueryRequest request) throws IOException {
+        request = buildRequest(adapter, request);
+        BinaryResponse response = client.query(request);
+        return adapter.deserialize(client, request, response);
+    }
+
+    //----- Asynchronous
+
+    public static <T> CompletableFuture<T> queryAsync(
+        ElasticsearchEsqlAsyncClient client, EsqlAdapter<T> adapter, String query, Object... params
+    ) {
+        return doQueryAsync(client, adapter, buildRequest(adapter, query, params));
+    }
+
+    public static <T> CompletableFuture<T> queryAsync(
+        ElasticsearchEsqlAsyncClient client, EsqlAdapter<T> adapter, QueryRequest request
+    ) {
+        return doQueryAsync(client, adapter, buildRequest(adapter, request));
+    }
+
+    private static <T> CompletableFuture<T> doQueryAsync(
+        ElasticsearchEsqlAsyncClient client, EsqlAdapter<T> adapter, QueryRequest request
+    ) {
+        return client
+            .query(request)
+            .thenApply(r -> {
+                try {
+                    return adapter.deserialize(client, request, r);
+                } catch (IOException e) {
+                    throw new RuntimeException(e);
+                }
+            });
+    }
+
+    //----- Utilities
+
+    private static QueryRequest buildRequest(EsqlAdapter<?> adapter, String query, Object... params) {
+        return QueryRequest.of(esql -> esql
+            .format(adapter.format())
+            .columnar(adapter.columnar())
+            .query(query)
+            .params(asFieldValues(params))
+        );
+    }
+
+    private static QueryRequest buildRequest(EsqlAdapter<?> adapter, QueryRequest request) {
+        return QueryRequest.of(q -> q
+            // Set/override format and columnar
+            .format(adapter.format())
+            .columnar(adapter.columnar())
+
+            .delimiter(request.delimiter())
+            .filter(request.filter())
+            .locale(request.locale())
+            .params(request.params())
+            .query(request.query())
+        );
+    }
+
+    private static List<FieldValue> asFieldValues(Object... objects) {
+
+        List<FieldValue> result = new ArrayList<>(objects.length);
+        for (Object object: objects) {
+            result.add(FieldValue.of(JsonData.of(object)));
+        }
+
+        return result;
+    }
+}

java-client/src/main-flavored/java/co/elastic/clients/elasticsearch/_helpers/esql/EsqlMetadata.java

@@ -0,0 +1,77 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. 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 co.elastic.clients.elasticsearch._helpers.esql;
+
+import co.elastic.clients.json.JsonpDeserializable;
+import co.elastic.clients.json.JsonpDeserializer;
+import co.elastic.clients.json.ObjectBuilderDeserializer;
+import co.elastic.clients.json.ObjectDeserializer;
+import co.elastic.clients.util.ObjectBuilder;
+import co.elastic.clients.util.ObjectBuilderBase;
+
+import java.util.List;
+
+public class EsqlMetadata {
+
+    @JsonpDeserializable
+    public static class EsqlColumn {
+        private String name;
+        private String type;
+
+        public String name() {
+            return name;
+        }
+
+        public String type() {
+            return type;
+        }
+
+        public static class Builder extends ObjectBuilderBase implements ObjectBuilder<EsqlColumn> {
+            EsqlColumn object = new EsqlColumn();
+
+            public Builder name(String value) {
+                object.name = value;
+                return this;
+            }
+
+            public Builder type(String value) {
+                object.type = value;
+                return this;
+            }
+
+            @Override
+            public EsqlColumn build() {
+                _checkSingleUse();
+                return object;
+            }
+        }
+
+        public static final JsonpDeserializer<EsqlColumn> _DESERIALIZER = ObjectBuilderDeserializer.lazy(
+            EsqlColumn.Builder::new, EsqlColumn::setupEsqlColumnDeserializer
+        );
+
+        protected static void setupEsqlColumnDeserializer(ObjectDeserializer<EsqlColumn.Builder> op) {
+            op.add(EsqlColumn.Builder::name, JsonpDeserializer.stringDeserializer(), "name");
+            op.add(EsqlColumn.Builder::type, JsonpDeserializer.stringDeserializer(), "type");
+        }
+    }
+
+    public List<EsqlColumn> columns;
+}