Prometheus: Add query_range REST endpoint backed by ES|QL PROMQL command

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/EsqlActionIT.java

@@ -57,8 +57,13 @@
 import org.elasticsearch.xpack.core.esql.action.ColumnInfo;
 import org.elasticsearch.xpack.esql.VerificationException;
 import org.elasticsearch.xpack.esql.analysis.AnalyzerSettings;
+import org.elasticsearch.xpack.esql.core.expression.Alias;
+import org.elasticsearch.xpack.esql.core.expression.Literal;
+import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
 import org.elasticsearch.xpack.esql.parser.ParsingException;
+import org.elasticsearch.xpack.esql.plan.EsqlStatement;
+import org.elasticsearch.xpack.esql.plan.logical.Row;
 import org.elasticsearch.xpack.esql.planner.PlannerSettings;
 import org.elasticsearch.xpack.esql.plugin.QueryPragmas;
 import org.junit.Before;
@@ -150,6 +155,22 @@ public void testRow() {
         }
     }
 
+    /**
+     * Verifies that a pre-built {@link EsqlStatement} supplied via
+     * {@link EsqlQueryRequest#syncEsqlQueryRequestWithPlan} is executed
+     * without going through ES|QL string parsing.
+     */
+    public void testRowWithParsedStatement() {
+        var plan = new Row(Source.EMPTY, List.of(new Alias(Source.EMPTY, "x", new Literal(Source.EMPTY, 1, DataType.INTEGER))));
+        var statement = new EsqlStatement(plan, List.of());
+        EsqlQueryRequest request = EsqlQueryRequest.syncEsqlQueryRequestWithPlan(statement);
+        request.pragmas(getPragmas());
+        try (EsqlQueryResponse response = run(request)) {
+            assertThat(response.columns(), equalTo(List.of(new ColumnInfoImpl("x", "integer", null))));
+            assertEquals(List.of(List.of(1)), getValuesList(response));
+        }
+    }
+
     public void testRowWithFilter() {
         long value = randomLongBetween(0, Long.MAX_VALUE);
         try (EsqlQueryResponse response = run(syncEsqlQueryRequest("ROW " + value).filter(randomQueryFilter()))) {

x-pack/plugin/esql/src/main/antlr/parser/Promql.g4

@@ -7,7 +7,9 @@
 parser grammar Promql;
 
 promqlCommand
-    : PROMQL promqlParam* (valueName ASSIGN)? LP promqlQueryPart+ RP
+    : PROMQL promqlParam* (valueName ASSIGN)? LP NAMED_OR_POSITIONAL_PARAM RP  // ?param as the entire PromQL expression (parenthesized)
+    | PROMQL promqlParam* (valueName ASSIGN)? NAMED_OR_POSITIONAL_PARAM        // ?param as the entire PromQL expression (unparenthesized)
+    | PROMQL promqlParam* (valueName ASSIGN)? LP promqlQueryPart+ RP
     | PROMQL promqlParam* promqlQueryPart+
     ;
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlQueryRequest.java

@@ -24,6 +24,7 @@
 import org.elasticsearch.xpack.core.async.AsyncExecutionId;
 import org.elasticsearch.xpack.esql.Column;
 import org.elasticsearch.xpack.esql.parser.QueryParams;
+import org.elasticsearch.xpack.esql.plan.EsqlStatement;
 import org.elasticsearch.xpack.esql.plugin.EsqlQueryStatus;
 import org.elasticsearch.xpack.esql.plugin.QueryPragmas;
 
@@ -66,6 +67,14 @@ public class EsqlQueryRequest extends org.elasticsearch.xpack.core.esql.action.E
      */
     private final Map<String, Map<String, Column>> tables = new TreeMap<>();
 
+    /**
+     * An optional pre-built statement that bypasses ES|QL string parsing.
+     * This is transient and never serialized over the wire. It's used by internal callers
+     * (such as the Prometheus REST endpoints) that construct a {@link EsqlStatement} directly
+     * instead of going through ES|QL string construction and parsing.
+     */
+    private EsqlStatement parsedStatement;
+
     public static EsqlQueryRequest syncEsqlQueryRequest(String query) {
         return new EsqlQueryRequest(false, query);
     }
@@ -74,6 +83,17 @@ public static EsqlQueryRequest asyncEsqlQueryRequest(String query) {
         return new EsqlQueryRequest(true, query);
     }
 
+    /**
+     * Creates a synchronous request with a pre-built statement, bypassing ES|QL string parsing.
+     * The query string is only used for logging/display since the plan is already built.
+     */
+    public static EsqlQueryRequest syncEsqlQueryRequestWithPlan(EsqlStatement statement) {
+        String queryText = statement.plan().sourceText();
+        EsqlQueryRequest request = new EsqlQueryRequest(false, queryText.isEmpty() ? "[pre-built plan]" : queryText);
+        request.parsedStatement = statement;
+        return request;
+    }
+
     private EsqlQueryRequest(boolean async, String query) {
         this.async = async;
         this.query = query;
@@ -119,6 +139,13 @@ public String query() {
         return query;
     }
 
+    /**
+     * Returns the pre-built statement, or {@code null} if the query string should be parsed.
+     */
+    public EsqlStatement parsedStatement() {
+        return parsedStatement;
+    }
+
     public boolean async() {
         return async;
     }