EQL: Introduce basic execution pipeline (elastic#51809)

Add main classes that form the 'execution' pipeline are added - most of
them have no functionality; the purpose of this PR is to add flesh out
the contract between the various moving parts so that work can start on
them independently.

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/analysis/Analyzer.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.eql.analysis;
+
+import org.elasticsearch.xpack.ql.expression.function.FunctionRegistry;
+import org.elasticsearch.xpack.ql.plan.logical.LogicalPlan;
+import org.elasticsearch.xpack.ql.rule.RuleExecutor;
+
+import java.util.Collection;
+
+import static java.util.Arrays.asList;
+
+public class Analyzer extends RuleExecutor<LogicalPlan> {
+
+    private final FunctionRegistry functionRegistry;
+    private final Verifier verifier;
+
+    public Analyzer(FunctionRegistry functionRegistry, Verifier verifier) {
+        this.functionRegistry = functionRegistry;
+        this.verifier = verifier;
+    }
+
+    @Override
+    protected Iterable<RuleExecutor<LogicalPlan>.Batch> batches() {
+        Batch resolution = new Batch("Resolution");
+
+        return asList(resolution);
+    }
+
+    public LogicalPlan analyze(LogicalPlan plan) {
+        return verify(execute(plan));
+    }
+
+    private LogicalPlan verify(LogicalPlan plan) {
+        Collection<Failure> failures = verifier.verify(plan);
+        if (!failures.isEmpty()) {
+            throw new VerificationException(failures);
+        }
+        return plan;
+    }
+}

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/analysis/Failure.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.eql.analysis;
+
+import org.elasticsearch.xpack.ql.tree.Node;
+
+import java.util.Objects;
+
+import static org.elasticsearch.common.logging.LoggerMessageFormat.format;
+
+class Failure {
+
+    private final Node<?> node;
+    private final String message;
+
+    Failure(Node<?> node, String message) {
+        this.node = node;
+        this.message = message;
+    }
+
+    Node<?> node() {
+        return node;
+    }
+
+    String message() {
+        return message;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(message, node);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+
+        Failure other = (Failure) obj;
+        return Objects.equals(message, other.message) && Objects.equals(node, other.node);
+    }
+
+    @Override
+    public String toString() {
+        return message;
+    }
+
+    static Failure fail(Node<?> source, String message, Object... args) {
+        return new Failure(source, format(message, args));
+    }
+}

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/analysis/PreAnalyzer.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.eql.analysis;
+
+import org.elasticsearch.xpack.ql.index.IndexResolution;
+import org.elasticsearch.xpack.ql.plan.logical.EsRelation;
+import org.elasticsearch.xpack.ql.plan.logical.LogicalPlan;
+import org.elasticsearch.xpack.ql.plan.logical.UnresolvedRelation;
+
+public class PreAnalyzer {
+
+    public LogicalPlan preAnalyze(LogicalPlan plan, IndexResolution indices) {
+        if (plan.analyzed() == false) {
+            // FIXME: includeFrozen needs to be set already
+            plan = plan.transformUp(r -> new EsRelation(r.source(), indices.get(), false), UnresolvedRelation.class);
+            plan.forEachUp(LogicalPlan::setPreAnalyzed);
+        }
+        return plan;
+    }
+}

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/analysis/VerificationException.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.eql.analysis;
+
+import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.xpack.eql.EqlClientException;
+import org.elasticsearch.xpack.ql.tree.Location;
+import org.elasticsearch.xpack.ql.util.StringUtils;
+
+import java.util.Collection;
+import java.util.stream.Collectors;
+
+public class VerificationException extends EqlClientException {
+
+    protected VerificationException(Collection<Failure> sources) {
+        super(asMessage(sources));
+    }
+
+    private static String asMessage(Collection<Failure> failures) {
+        return failures.stream().map(f -> {
+            Location l = f.node().source().source();
+            return "line " + l.getLineNumber() + ":" + l.getColumnNumber() + ": " + f.message();
+        }).collect(Collectors.joining(StringUtils.NEW_LINE, "Found " + failures.size() + " problem(s)\n", StringUtils.EMPTY));
+    }
+
+    @Override
+    public RestStatus status() {
+        return RestStatus.BAD_REQUEST;
+    }
+}

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/analysis/Verifier.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.eql.analysis;
+
+import org.elasticsearch.xpack.ql.capabilities.Unresolvable;
+import org.elasticsearch.xpack.ql.expression.Attribute;
+import org.elasticsearch.xpack.ql.expression.UnresolvedAttribute;
+import org.elasticsearch.xpack.ql.plan.logical.LogicalPlan;
+import org.elasticsearch.xpack.ql.tree.Node;
+import org.elasticsearch.xpack.ql.type.DataTypes;
+import org.elasticsearch.xpack.ql.util.StringUtils;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static java.util.stream.Collectors.toMap;
+import static org.elasticsearch.xpack.eql.analysis.Failure.fail;
+
+/**
+ * The verifier has the role of checking the analyzed tree for failures and build a list of failures following this check.
+ * It is created in the plan executor along with the metrics instance passed as constructor parameter.
+ */
+public class Verifier {
+
+    public Map<Node<?>, String> verifyFailures(LogicalPlan plan) {
+        Collection<Failure> failures = verify(plan);
+        return failures.stream().collect(toMap(Failure::node, Failure::message));
+    }
+
+    Collection<Failure> verify(LogicalPlan plan) {
+        Set<Failure> failures = new LinkedHashSet<>();
+
+        // start bottom-up
+        plan.forEachUp(p -> {
+            if (p.analyzed()) {
+                return;
+            }
+
+            // if the children are unresolved, so will this node; counting it will only add noise
+            if (p.childrenResolved() == false) {
+                return;
+            }
+
+            Set<Failure> localFailures = new LinkedHashSet<>();
+
+            if (p instanceof Unresolvable) {
+                localFailures.add(fail(p, ((Unresolvable) p).unresolvedMessage()));
+            } else {
+                p.forEachExpressions(e -> {
+                    // everything is fine, skip expression
+                    if (e.resolved()) {
+                        return;
+                    }
+
+                    e.forEachUp(ae -> {
+                        // we're only interested in the children
+                        if (ae.childrenResolved() == false) {
+                            return;
+                        }
+                        if (ae instanceof Unresolvable) {
+                            // handle Attributes differently to provide more context
+                            if (ae instanceof UnresolvedAttribute) {
+                                UnresolvedAttribute ua = (UnresolvedAttribute) ae;
+                                // only work out the synonyms for raw unresolved attributes
+                                if (ua.customMessage() == false) {
+                                    boolean useQualifier = ua.qualifier() != null;
+                                    List<String> potentialMatches = new ArrayList<>();
+                                    for (Attribute a : p.inputSet()) {
+                                        String nameCandidate = useQualifier ? a.qualifiedName() : a.name();
+                                        // add only primitives (object types would only result in another error)
+                                        if (DataTypes.isUnsupported(a.dataType()) == false && DataTypes.isPrimitive(a.dataType())) {
+                                            potentialMatches.add(nameCandidate);
+                                        }
+                                    }
+
+                                    List<String> matches = StringUtils.findSimilar(ua.qualifiedName(), potentialMatches);
+                                    if (matches.isEmpty() == false) {
+                                        ae = ua.withUnresolvedMessage(UnresolvedAttribute.errorMessage(ua.qualifiedName(), matches));
+                                    }
+                                }
+                            }
+
+                            localFailures.add(fail(ae, ((Unresolvable) ae).unresolvedMessage()));
+                            return;
+                        }
+                        // type resolution
+                        if (ae.typeResolved().unresolved()) {
+                            localFailures.add(fail(ae, ae.typeResolved().message()));
+                        }
+
+                    });
+                });
+            }
+        });
+
+        return failures;
+    }
+}

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/execution/PlanExecutor.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.eql.execution;
+
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.client.Client;
+import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
+import org.elasticsearch.xpack.eql.analysis.Analyzer;
+import org.elasticsearch.xpack.eql.analysis.PreAnalyzer;
+import org.elasticsearch.xpack.eql.analysis.Verifier;
+import org.elasticsearch.xpack.eql.optimizer.Optimizer;
+import org.elasticsearch.xpack.eql.planner.Planner;
+import org.elasticsearch.xpack.eql.session.Configuration;
+import org.elasticsearch.xpack.eql.session.EqlSession;
+import org.elasticsearch.xpack.eql.session.Results;
+import org.elasticsearch.xpack.ql.expression.function.FunctionRegistry;
+import org.elasticsearch.xpack.ql.index.IndexResolver;
+
+import java.util.List;
+
+import static org.elasticsearch.action.ActionListener.wrap;
+
+public class PlanExecutor {
+    private final Client client;
+    private final NamedWriteableRegistry writableRegistry;
+
+    private final IndexResolver indexResolver;
+    private final FunctionRegistry functionRegistry;
+
+    private final PreAnalyzer preAnalyzer;
+    private final Analyzer analyzer;
+    private final Optimizer optimizer;
+    private final Planner planner;
+
+    public PlanExecutor(Client client, IndexResolver indexResolver, NamedWriteableRegistry writeableRegistry) {
+        this.client = client;
+        this.writableRegistry = writeableRegistry;
+
+        this.indexResolver = indexResolver;
+        this.functionRegistry = null;
+
+        this.preAnalyzer = new PreAnalyzer();
+        this.analyzer = new Analyzer(functionRegistry, new Verifier());
+        this.optimizer = new Optimizer();
+        this.planner = new Planner();
+    }
+
+    private EqlSession newSession(Configuration cfg) {
+        return new EqlSession(client, cfg, indexResolver, preAnalyzer, analyzer, optimizer, planner, this);
+    }
+
+    public void eql(Configuration cfg, String eql, List<Object> params, ActionListener<Results> listener) {
+        newSession(cfg).eql(eql, params, wrap(listener::onResponse, listener::onFailure));
+    }
+}

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/optimizer/Optimizer.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.eql.optimizer;
+
+import org.elasticsearch.xpack.ql.plan.logical.LogicalPlan;
+import org.elasticsearch.xpack.ql.rule.RuleExecutor;
+
+import static java.util.Collections.emptyList;
+
+public class Optimizer extends RuleExecutor<LogicalPlan> {
+
+    public LogicalPlan optimize(LogicalPlan verified) {
+        return verified.optimized() ? verified : execute(verified);
+    }
+
+    @Override
+    protected Iterable<RuleExecutor<LogicalPlan>.Batch> batches() {
+        return emptyList();
+    }
+}

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/plan/physical/PhysicalPlan.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.eql.plan.physical;
+
+import org.elasticsearch.xpack.eql.session.Executable;
+import org.elasticsearch.xpack.ql.plan.QueryPlan;
+import org.elasticsearch.xpack.ql.tree.Source;
+
+import java.util.List;
+
+/**
+ * A PhysicalPlan is "how" a LogicalPlan (the "what") actually gets translated into one or more queries.
+ *
+ * LogicalPlan = I want to get from DEN to SFO
+ * PhysicalPlan = take Delta, DEN to SJC, then SJC to SFO
+ */
+public abstract class PhysicalPlan extends QueryPlan<PhysicalPlan> implements Executable {
+
+    public PhysicalPlan(Source source, List<PhysicalPlan> children) {
+        super(source, children);
+    }
+
+    @Override
+    public abstract int hashCode();
+
+    @Override
+    public abstract boolean equals(Object obj);
+}