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The plugin that powers ESQL for Elasticsearch
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0; you may not use this file except in compliance with the Elastic License
* 2.0.
*/
package org.elasticsearch.xpack.esql.analysis;
import org.elasticsearch.xpack.esql.core.capabilities.Unresolvable;
import org.elasticsearch.xpack.esql.core.common.Failure;
import org.elasticsearch.xpack.esql.core.expression.Alias;
import org.elasticsearch.xpack.esql.core.expression.Attribute;
import org.elasticsearch.xpack.esql.core.expression.AttributeMap;
import org.elasticsearch.xpack.esql.core.expression.AttributeSet;
import org.elasticsearch.xpack.esql.core.expression.Expression;
import org.elasticsearch.xpack.esql.core.expression.Expressions;
import org.elasticsearch.xpack.esql.core.expression.FieldAttribute;
import org.elasticsearch.xpack.esql.core.expression.NamedExpression;
import org.elasticsearch.xpack.esql.core.expression.TypeResolutions;
import org.elasticsearch.xpack.esql.core.expression.predicate.BinaryOperator;
import org.elasticsearch.xpack.esql.core.expression.predicate.operator.comparison.BinaryComparison;
import org.elasticsearch.xpack.esql.core.plan.logical.Limit;
import org.elasticsearch.xpack.esql.core.plan.logical.LogicalPlan;
import org.elasticsearch.xpack.esql.core.plan.logical.OrderBy;
import org.elasticsearch.xpack.esql.core.plan.logical.UnaryPlan;
import org.elasticsearch.xpack.esql.core.type.DataType;
import org.elasticsearch.xpack.esql.expression.function.UnsupportedAttribute;
import org.elasticsearch.xpack.esql.expression.function.aggregate.AggregateFunction;
import org.elasticsearch.xpack.esql.expression.function.aggregate.Rate;
import org.elasticsearch.xpack.esql.expression.function.grouping.GroupingFunction;
import org.elasticsearch.xpack.esql.expression.predicate.operator.arithmetic.Neg;
import org.elasticsearch.xpack.esql.expression.predicate.operator.comparison.Equals;
import org.elasticsearch.xpack.esql.expression.predicate.operator.comparison.NotEquals;
import org.elasticsearch.xpack.esql.plan.logical.Aggregate;
import org.elasticsearch.xpack.esql.plan.logical.Enrich;
import org.elasticsearch.xpack.esql.plan.logical.Eval;
import org.elasticsearch.xpack.esql.plan.logical.Lookup;
import org.elasticsearch.xpack.esql.plan.logical.Project;
import org.elasticsearch.xpack.esql.plan.logical.RegexExtract;
import org.elasticsearch.xpack.esql.plan.logical.Row;
import org.elasticsearch.xpack.esql.stats.FeatureMetric;
import org.elasticsearch.xpack.esql.stats.Metrics;
import org.elasticsearch.xpack.esql.type.EsqlDataTypes;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import java.util.function.Consumer;
import java.util.stream.Stream;
import static org.elasticsearch.xpack.esql.core.analyzer.VerifierChecks.checkFilterConditionType;
import static org.elasticsearch.xpack.esql.core.common.Failure.fail;
import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.FIRST;
public class Verifier {
private final Metrics metrics;
public Verifier(Metrics metrics) {
this.metrics = metrics;
}
/**
* Verify that a {@link LogicalPlan} can be executed.
*
* @param plan The logical plan to be verified
* @param partialMetrics a bitset indicating a certain command (or "telemetry feature") is present in the query
* @return a collection of verification failures; empty if and only if the plan is valid
*/
Collection verify(LogicalPlan plan, BitSet partialMetrics) {
assert partialMetrics != null;
Set failures = new LinkedHashSet<>();
// alias map, collected during the first iteration for better error messages
AttributeMap aliases = new AttributeMap<>();
// quick verification for unresolved attributes
plan.forEachUp(p -> {
// if the children are unresolved, so will this node; counting it will only add noise
if (p.childrenResolved() == false) {
return;
}
if (p instanceof Unresolvable u) {
failures.add(fail(p, u.unresolvedMessage()));
}
// p is resolved, skip
else if (p.resolved()) {
p.forEachExpressionUp(Alias.class, a -> aliases.put(a.toAttribute(), a.child()));
return;
}
Consumer unresolvedExpressions = 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 u) {
// special handling for Project and unsupported types
if (p instanceof Project == false || u instanceof UnsupportedAttribute == false) {
failures.add(fail(ae, u.unresolvedMessage()));
}
}
if (ae.typeResolved().unresolved()) {
failures.add(fail(ae, ae.typeResolved().message()));
}
});
};
// aggregates duplicate grouping inside aggs - to avoid potentially confusing messages, we only check the aggregates
if (p instanceof Aggregate agg) {
// do groupings first
var groupings = agg.groupings();
groupings.forEach(unresolvedExpressions);
// followed by just the aggregates (to avoid going through the groups again)
var aggs = agg.aggregates();
int size = aggs.size() - groupings.size();
aggs.subList(0, size).forEach(unresolvedExpressions);
}
// similar approach for Lookup
else if (p instanceof Lookup lookup) {
// first check the table
var tableName = lookup.tableName();
if (tableName instanceof Unresolvable u) {
failures.add(fail(tableName, u.unresolvedMessage()));
}
// only after that check the match fields
else {
lookup.matchFields().forEach(unresolvedExpressions);
}
}
else {
p.forEachExpression(unresolvedExpressions);
}
});
// in case of failures bail-out as all other checks will be redundant
if (failures.isEmpty() == false) {
return failures;
}
// Concrete verifications
plan.forEachDown(p -> {
// if the children are unresolved, so will this node; counting it will only add noise
if (p.childrenResolved() == false) {
return;
}
checkFilterConditionType(p, failures);
checkAggregate(p, failures);
checkRegexExtractOnlyOnStrings(p, failures);
checkRow(p, failures);
checkEvalFields(p, failures);
checkOperationsOnUnsignedLong(p, failures);
checkBinaryComparison(p, failures);
checkForSortOnSpatialTypes(p, failures);
});
checkRemoteEnrich(plan, failures);
// gather metrics
if (failures.isEmpty()) {
gatherMetrics(plan, partialMetrics);
}
return failures;
}
private static void checkAggregate(LogicalPlan p, Set failures) {
if (p instanceof Aggregate agg) {
List groupings = agg.groupings();
AttributeSet groupRefs = new AttributeSet();
// check grouping
// The grouping can not be an aggregate function
groupings.forEach(e -> {
e.forEachUp(g -> {
if (g instanceof AggregateFunction af) {
failures.add(fail(g, "cannot use an aggregate [{}] for grouping", af));
} else if (g instanceof GroupingFunction gf) {
gf.children()
.forEach(
c -> c.forEachDown(
GroupingFunction.class,
inner -> failures.add(
fail(
inner,
"cannot nest grouping functions; found [{}] inside [{}]",
inner.sourceText(),
gf.sourceText()
)
)
)
);
}
});
// keep the grouping attributes (common case)
Attribute attr = Expressions.attribute(e);
if (attr != null) {
groupRefs.add(attr);
}
if (e instanceof FieldAttribute f && f.dataType().isCounter()) {
failures.add(fail(e, "cannot group by on [{}] type for grouping [{}]", f.dataType().typeName(), e.sourceText()));
}
});
// check aggregates - accept only aggregate functions or expressions over grouping
// don't allow the group by itself to avoid duplicates in the output
// and since the groups are copied, only look at the declared aggregates
List aggs = agg.aggregates();
aggs.subList(0, aggs.size() - groupings.size()).forEach(e -> {
var exp = Alias.unwrap(e);
if (exp.foldable()) {
failures.add(fail(exp, "expected an aggregate function but found [{}]", exp.sourceText()));
}
// traverse the tree to find invalid matches
checkInvalidNamedExpressionUsage(exp, groupings, groupRefs, failures, 0);
});
if (agg.aggregateType() == Aggregate.AggregateType.METRICS) {
aggs.forEach(a -> checkRateAggregates(a, 0, failures));
} else {
agg.forEachExpression(
Rate.class,
r -> failures.add(fail(r, "the rate aggregate[{}] can only be used within the metrics command", r.sourceText()))
);
}
} else {
p.forEachExpression(
GroupingFunction.class,
gf -> failures.add(fail(gf, "cannot use grouping function [{}] outside of a STATS command", gf.sourceText()))
);
}
}
private static void checkRateAggregates(Expression expr, int nestedLevel, Set failures) {
if (expr instanceof AggregateFunction) {
nestedLevel++;
}
if (expr instanceof Rate r) {
if (nestedLevel != 2) {
failures.add(
fail(
expr,
"the rate aggregate [{}] can only be used within the metrics command and inside another aggregate",
r.sourceText()
)
);
}
}
for (Expression child : expr.children()) {
checkRateAggregates(child, nestedLevel, failures);
}
}
// traverse the expression and look either for an agg function or a grouping match
// stop either when no children are left, the leafs are literals or a reference attribute is given
private static void checkInvalidNamedExpressionUsage(
Expression e,
List groups,
AttributeSet groupRefs,
Set failures,
int level
) {
// found an aggregate, constant or a group, bail out
if (e instanceof AggregateFunction af) {
af.field().forEachDown(AggregateFunction.class, f -> {
// rate aggregate is allowed to be inside another aggregate
if (f instanceof Rate == false) {
failures.add(fail(f, "nested aggregations [{}] not allowed inside other aggregations [{}]", f, af));
}
});
} else if (e instanceof GroupingFunction gf) {
// optimizer will later unroll expressions with aggs and non-aggs with a grouping function into an EVAL, but that will no longer
// be verified (by check above in checkAggregate()), so do it explicitly here
if (groups.stream().anyMatch(ex -> ex instanceof Alias a && a.child().semanticEquals(gf)) == false) {
failures.add(fail(gf, "can only use grouping function [{}] part of the BY clause", gf.sourceText()));
} else if (level == 0) {
addFailureOnGroupingUsedNakedInAggs(failures, gf, "function");
}
} else if (e.foldable()) {
// don't do anything
} else if (groups.contains(e) || groupRefs.contains(e)) {
if (level == 0) {
addFailureOnGroupingUsedNakedInAggs(failures, e, "key");
}
}
// if a reference is found, mark it as an error
else if (e instanceof NamedExpression ne) {
boolean foundInGrouping = false;
for (Expression g : groups) {
if (g.anyMatch(se -> se.semanticEquals(ne))) {
foundInGrouping = true;
failures.add(
fail(
e,
"column [{}] cannot be used as an aggregate once declared in the STATS BY grouping key [{}]",
ne.name(),
g.sourceText()
)
);
break;
}
}
if (foundInGrouping == false) {
failures.add(fail(e, "column [{}] must appear in the STATS BY clause or be used in an aggregate function", ne.name()));
}
}
// other keep on going
else {
for (Expression child : e.children()) {
checkInvalidNamedExpressionUsage(child, groups, groupRefs, failures, level + 1);
}
}
}
private static void addFailureOnGroupingUsedNakedInAggs(Set failures, Expression e, String element) {
failures.add(
fail(e, "grouping {} [{}] cannot be used as an aggregate once declared in the STATS BY clause", element, e.sourceText())
);
}
private static void checkRegexExtractOnlyOnStrings(LogicalPlan p, Set failures) {
if (p instanceof RegexExtract re) {
Expression expr = re.input();
DataType type = expr.dataType();
if (EsqlDataTypes.isString(type) == false) {
failures.add(
fail(
expr,
"{} only supports KEYWORD or TEXT values, found expression [{}] type [{}]",
re.getClass().getSimpleName(),
expr.sourceText(),
type
)
);
}
}
}
private static void checkRow(LogicalPlan p, Set failures) {
if (p instanceof Row row) {
row.fields().forEach(a -> {
if (EsqlDataTypes.isRepresentable(a.dataType()) == false) {
failures.add(fail(a, "cannot use [{}] directly in a row assignment", a.child().sourceText()));
}
});
}
}
private static void checkEvalFields(LogicalPlan p, Set failures) {
if (p instanceof Eval eval) {
eval.fields().forEach(field -> {
// check supported types
DataType dataType = field.dataType();
if (EsqlDataTypes.isRepresentable(dataType) == false) {
failures.add(
fail(field, "EVAL does not support type [{}] in expression [{}]", dataType.typeName(), field.child().sourceText())
);
}
// check no aggregate functions are used
field.forEachDown(AggregateFunction.class, af -> {
if (af instanceof Rate) {
failures.add(fail(af, "aggregate function [{}] not allowed outside METRICS command", af.sourceText()));
} else {
failures.add(fail(af, "aggregate function [{}] not allowed outside STATS command", af.sourceText()));
}
});
});
}
}
private static void checkOperationsOnUnsignedLong(LogicalPlan p, Set failures) {
p.forEachExpression(e -> {
Failure f = null;
if (e instanceof BinaryOperator bo) {
f = validateUnsignedLongOperator(bo);
} else if (e instanceof Neg neg) {
f = validateUnsignedLongNegation(neg);
}
if (f != null) {
failures.add(f);
}
});
}
private static void checkBinaryComparison(LogicalPlan p, Set failures) {
p.forEachExpression(BinaryComparison.class, bc -> {
Failure f = validateBinaryComparison(bc);
if (f != null) {
failures.add(f);
}
});
}
private void gatherMetrics(LogicalPlan plan, BitSet b) {
plan.forEachDown(p -> FeatureMetric.set(p, b));
for (int i = b.nextSetBit(0); i >= 0; i = b.nextSetBit(i + 1)) {
metrics.inc(FeatureMetric.values()[i]);
}
}
/**
* Limit QL's comparisons to types we support.
*/
public static Failure validateBinaryComparison(BinaryComparison bc) {
if (bc.left().dataType().isNumeric()) {
if (false == bc.right().dataType().isNumeric()) {
return fail(
bc,
"first argument of [{}] is [numeric] so second argument must also be [numeric] but was [{}]",
bc.sourceText(),
bc.right().dataType().typeName()
);
}
return null;
}
List allowed = new ArrayList<>();
allowed.add(DataType.KEYWORD);
allowed.add(DataType.TEXT);
allowed.add(DataType.IP);
allowed.add(DataType.DATETIME);
allowed.add(DataType.VERSION);
allowed.add(DataType.GEO_POINT);
allowed.add(DataType.GEO_SHAPE);
allowed.add(DataType.CARTESIAN_POINT);
allowed.add(DataType.CARTESIAN_SHAPE);
if (bc instanceof Equals || bc instanceof NotEquals) {
allowed.add(DataType.BOOLEAN);
}
Expression.TypeResolution r = TypeResolutions.isType(
bc.left(),
allowed::contains,
bc.sourceText(),
FIRST,
Stream.concat(Stream.of("numeric"), allowed.stream().map(DataType::typeName)).toArray(String[]::new)
);
if (false == r.resolved()) {
return fail(bc, r.message());
}
if (DataType.isString(bc.left().dataType()) && DataType.isString(bc.right().dataType())) {
return null;
}
if (bc.left().dataType() != bc.right().dataType()) {
return fail(
bc,
"first argument of [{}] is [{}] so second argument must also be [{}] but was [{}]",
bc.sourceText(),
bc.left().dataType().typeName(),
bc.left().dataType().typeName(),
bc.right().dataType().typeName()
);
}
return null;
}
/** Ensure that UNSIGNED_LONG types are not implicitly converted when used in arithmetic binary operator, as this cannot be done since:
* - unsigned longs are passed through the engine as longs, so/and
* - negative values cannot be represented (i.e. range [Long.MIN_VALUE, "abs"(Long.MIN_VALUE) + Long.MAX_VALUE] won't fit on 64 bits);
* - a conversion to double isn't possible, since upper range UL values can no longer be distinguished
* ex: (double) 18446744073709551615 == (double) 18446744073709551614
* - the implicit ESQL's Cast doesn't currently catch Exception and nullify the result.
* Let the user handle the operation explicitly.
*/
public static Failure validateUnsignedLongOperator(BinaryOperator bo) {
DataType leftType = bo.left().dataType();
DataType rightType = bo.right().dataType();
if ((leftType == DataType.UNSIGNED_LONG || rightType == DataType.UNSIGNED_LONG) && leftType != rightType) {
return fail(
bo,
"first argument of [{}] is [{}] and second is [{}]. [{}] can only be operated on together with another [{}]",
bo.sourceText(),
leftType.typeName(),
rightType.typeName(),
DataType.UNSIGNED_LONG.typeName(),
DataType.UNSIGNED_LONG.typeName()
);
}
return null;
}
/**
* Negating an unsigned long is invalid.
*/
private static Failure validateUnsignedLongNegation(Neg neg) {
DataType childExpressionType = neg.field().dataType();
if (childExpressionType.equals(DataType.UNSIGNED_LONG)) {
return fail(
neg,
"negation unsupported for arguments of type [{}] in expression [{}]",
childExpressionType.typeName(),
neg.sourceText()
);
}
return null;
}
/**
* Makes sure that spatial types do not appear in sorting contexts.
*/
private static void checkForSortOnSpatialTypes(LogicalPlan p, Set localFailures) {
if (p instanceof OrderBy ob) {
ob.forEachExpression(Attribute.class, attr -> {
DataType dataType = attr.dataType();
if (EsqlDataTypes.isSpatial(dataType)) {
localFailures.add(fail(attr, "cannot sort on " + dataType.typeName()));
}
});
}
}
/**
* Ensure that no remote enrich is allowed after a reduction or an enrich with coordinator mode.
*
* TODO:
* For Limit and TopN, we can insert the same node after the remote enrich (also needs to move projections around)
* to eliminate this limitation. Otherwise, we force users to write queries that might not perform well.
* For example, `FROM test | ORDER @timestamp | LIMIT 10 | ENRICH _remote:` doesn't work.
* In that case, users have to write it as `FROM test | ENRICH _remote: | ORDER @timestamp | LIMIT 10`,
* which is equivalent to bringing all data to the coordinating cluster.
* We might consider implementing the actual remote enrich on the coordinating cluster, however, this requires
* retaining the originating cluster and restructing pages for routing, which might be complicated.
*/
private static void checkRemoteEnrich(LogicalPlan plan, Set failures) {
boolean[] agg = { false };
boolean[] limit = { false };
boolean[] enrichCoord = { false };
plan.forEachUp(UnaryPlan.class, u -> {
if (u instanceof Limit) {
limit[0] = true; // TODO: Make Limit then enrich_remote work
}
if (u instanceof Aggregate) {
agg[0] = true;
} else if (u instanceof Enrich enrich && enrich.mode() == Enrich.Mode.COORDINATOR) {
enrichCoord[0] = true;
}
if (u instanceof Enrich enrich && enrich.mode() == Enrich.Mode.REMOTE) {
if (limit[0]) {
failures.add(fail(enrich, "ENRICH with remote policy can't be executed after LIMIT"));
}
if (agg[0]) {
failures.add(fail(enrich, "ENRICH with remote policy can't be executed after STATS"));
}
if (enrichCoord[0]) {
failures.add(fail(enrich, "ENRICH with remote policy can't be executed after another ENRICH with coordinator policy"));
}
}
});
}
}
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