ESQL: Qualifiers syntax

server/src/main/java/org/elasticsearch/TransportVersions.java

@@ -369,6 +369,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion SCRIPT_RESCORER = def(9_143_0_00);
     public static final TransportVersion ESQL_LOOKUP_OPERATOR_EMITTED_ROWS = def(9_144_0_00);
     public static final TransportVersion ALLOCATION_DECISION_NOT_PREFERRED = def(9_145_0_00);
+    public static final TransportVersion ESQL_QUALIFIERS_IN_ATTRIBUTES = def(9_146_0_00);
 
     /*
      * STOP! READ THIS FIRST! No, really,

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/Alias.java

@@ -125,7 +125,7 @@ public DataType dataType() {
     public Attribute toAttribute() {
         if (lazyAttribute == null) {
             lazyAttribute = resolved()
-                ? new ReferenceAttribute(source(), name(), dataType(), nullable(), id(), synthetic())
+                ? new ReferenceAttribute(source(), null, name(), dataType(), nullable(), id(), synthetic())
                 : new UnresolvedAttribute(source(), name());
         }
         return lazyAttribute;

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/Attribute.java

@@ -6,14 +6,19 @@
  */
 package org.elasticsearch.xpack.esql.core.expression;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
+import org.elasticsearch.xpack.esql.core.util.PlanStreamInput;
+import org.elasticsearch.xpack.esql.core.util.PlanStreamOutput;
 
+import java.io.IOException;
 import java.util.List;
 import java.util.Objects;
 
 import static java.util.Collections.emptyList;
+import static org.elasticsearch.TransportVersions.ESQL_QUALIFIERS_IN_ATTRIBUTES;
 
 /**
  * {@link Expression}s that can be materialized and describe properties of the derived table.
@@ -33,19 +38,40 @@ public abstract class Attribute extends NamedExpression {
      */
     protected static final String SYNTHETIC_ATTRIBUTE_NAME_PREFIX = "$$";
 
-    // can the attr be null - typically used in JOINs
+    // can the attr be null
     private final Nullability nullability;
+    private final String qualifier;
 
     public Attribute(Source source, String name, @Nullable NameId id) {
         this(source, name, Nullability.TRUE, id);
     }
 
+    public Attribute(Source source, @Nullable String qualifier, String name, @Nullable NameId id) {
+        this(source, qualifier, name, Nullability.TRUE, id);
+    }
+
     public Attribute(Source source, String name, Nullability nullability, @Nullable NameId id) {
-        this(source, name, nullability, id, false);
+        this(source, null, name, nullability, id);
+    }
+
+    public Attribute(Source source, @Nullable String qualifier, String name, Nullability nullability, @Nullable NameId id) {
+        this(source, qualifier, name, nullability, id, false);
     }
 
     public Attribute(Source source, String name, Nullability nullability, @Nullable NameId id, boolean synthetic) {
+        this(source, null, name, nullability, id, synthetic);
+    }
+
+    public Attribute(
+        Source source,
+        @Nullable String qualifier,
+        String name,
+        Nullability nullability,
+        @Nullable NameId id,
+        boolean synthetic
+    ) {
         super(source, name, emptyList(), id, synthetic);
+        this.qualifier = qualifier;
         this.nullability = nullability;
     }
 
@@ -59,6 +85,14 @@ public final Expression replaceChildren(List<Expression> newChildren) {
         throw new UnsupportedOperationException("this type of node doesn't have any children to replace");
     }
 
+    public String qualifier() {
+        return qualifier;
+    }
+
+    public String qualifiedName() {
+        return qualifier != null ? "[" + qualifier + "].[" + name() + "]" : name();
+    }
+
     @Override
     public Nullability nullable() {
         return nullability;
@@ -70,26 +104,40 @@ public AttributeSet references() {
     }
 
     public Attribute withLocation(Source source) {
-        return Objects.equals(source(), source) ? this : clone(source, name(), dataType(), nullable(), id(), synthetic());
+        return Objects.equals(source(), source) ? this : clone(source, qualifier(), name(), dataType(), nullable(), id(), synthetic());
+    }
+
+    public Attribute withQualifier(String qualifier) {
+        return Objects.equals(qualifier, qualifier) ? this : clone(source(), qualifier, name(), dataType(), nullable(), id(), synthetic());
     }
 
     public Attribute withName(String name) {
-        return Objects.equals(name(), name) ? this : clone(source(), name, dataType(), nullable(), id(), synthetic());
+        return Objects.equals(name(), name) ? this : clone(source(), qualifier(), name, dataType(), nullable(), id(), synthetic());
     }
 
     public Attribute withNullability(Nullability nullability) {
-        return Objects.equals(nullable(), nullability) ? this : clone(source(), name(), dataType(), nullability, id(), synthetic());
+        return Objects.equals(nullable(), nullability)
+            ? this
+            : clone(source(), qualifier(), name(), dataType(), nullability, id(), synthetic());
     }
 
     public Attribute withId(NameId id) {
-        return clone(source(), name(), dataType(), nullable(), id, synthetic());
+        return clone(source(), qualifier(), name(), dataType(), nullable(), id, synthetic());
     }
 
     public Attribute withDataType(DataType type) {
-        return Objects.equals(dataType(), type) ? this : clone(source(), name(), type, nullable(), id(), synthetic());
+        return Objects.equals(dataType(), type) ? this : clone(source(), qualifier(), name(), type, nullable(), id(), synthetic());
     }
 
-    protected abstract Attribute clone(Source source, String name, DataType type, Nullability nullability, NameId id, boolean synthetic);
+    protected abstract Attribute clone(
+        Source source,
+        String qualifier,
+        String name,
+        DataType type,
+        Nullability nullability,
+        NameId id,
+        boolean synthetic
+    );
 
     @Override
     public Attribute toAttribute() {
@@ -108,24 +156,24 @@ public boolean semanticEquals(Expression other) {
 
     @Override
     protected Expression canonicalize() {
-        return clone(Source.EMPTY, name(), dataType(), nullability, id(), synthetic());
+        return clone(Source.EMPTY, qualifier(), name(), dataType(), nullability, id(), synthetic());
     }
 
     @Override
     @SuppressWarnings("checkstyle:EqualsHashCode")// equals is implemented in parent. See innerEquals instead
     public int hashCode() {
-        return Objects.hash(super.hashCode(), nullability);
+        return Objects.hash(super.hashCode(), qualifier, nullability);
     }
 
     @Override
     protected boolean innerEquals(Object o) {
         var other = (Attribute) o;
-        return super.innerEquals(other) && Objects.equals(nullability, other.nullability);
+        return super.innerEquals(other) && Objects.equals(qualifier, other.qualifier) && Objects.equals(nullability, other.nullability);
     }
 
     @Override
     public String toString() {
-        return name() + "{" + label() + (synthetic() ? "$" : "") + "}" + "#" + id();
+        return qualifiedName() + "{" + label() + (synthetic() ? "$" : "") + "}" + "#" + id();
     }
 
     @Override
@@ -154,4 +202,22 @@ public static boolean dataTypeEquals(List<Attribute> left, List<Attribute> right
      * @return true if the attribute represents a TSDB dimension type
      */
     public abstract boolean isDimension();
+
+    protected void checkAndSerializeQualifier(PlanStreamOutput out, TransportVersion version) throws IOException {
+        if (version.onOrAfter(ESQL_QUALIFIERS_IN_ATTRIBUTES)) {
+            out.writeOptionalCachedString(qualifier());
+        } else if (qualifier() != null) {
+            // Non-null qualifier means the query specifically defined one. Old nodes don't know what to do with it and just writing
+            // null would lose information and lead to undefined, likely invalid queries.
+            // IllegalArgumentException returns a 400 to the user, which is what we want here.
+            throw new IllegalArgumentException("Trying to serialize an Attribute with a qualifier to an old node");
+        }
+    }
+
+    protected static String readQualifier(PlanStreamInput in, TransportVersion version) throws IOException {
+        if (version.onOrAfter(ESQL_QUALIFIERS_IN_ATTRIBUTES)) {
+            return in.readOptionalCachedString();
+        }
+        return null;
+    }
 }

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/EmptyAttribute.java

@@ -35,7 +35,15 @@ public String getWriteableName() {
     }
 
     @Override
-    protected Attribute clone(Source source, String name, DataType type, Nullability nullability, NameId id, boolean synthetic) {
+    protected Attribute clone(
+        Source source,
+        String qualifier,
+        String name,
+        DataType type,
+        Nullability nullability,
+        NameId id,
+        boolean synthetic
+    ) {
         return this;
     }
 

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/Expressions.java

@@ -20,10 +20,6 @@ public final class Expressions {
 
     private Expressions() {}
 
-    public static NamedExpression wrapAsNamed(Expression exp) {
-        return exp instanceof NamedExpression ne ? ne : new Alias(exp.source(), exp.sourceText(), exp);
-    }
-
     public static List<Attribute> asAttributes(List<? extends NamedExpression> named) {
         if (named.isEmpty()) {
             return emptyList();
@@ -109,7 +105,9 @@ public static AttributeSet references(List<? extends Expression> exps) {
     }
 
     public static String name(Expression e) {
-        return e instanceof NamedExpression ne ? ne.name() : e.sourceText();
+        return e instanceof Attribute attr && attr.qualifier() != null ? attr.qualifiedName()
+            : e instanceof NamedExpression ne ? ne.name()
+            : e.sourceText();
     }
 
     /**

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/FieldAttribute.java

@@ -55,28 +55,40 @@ public record FieldName(String string) {};
     private final EsField field;
     protected FieldName lazyFieldName;
 
+    @Deprecated
+    /**
+     * For testing only
+     */
     public FieldAttribute(Source source, String name, EsField field) {
-        this(source, null, name, field);
+        this(source, null, null, name, field, Nullability.TRUE, null, false);
     }
 
-    public FieldAttribute(Source source, @Nullable String parentName, String name, EsField field) {
-        this(source, parentName, name, field, Nullability.TRUE, null, false);
+    public FieldAttribute(
+        Source source,
+        @Nullable String parentName,
+        @Nullable String qualifier,
+        String name,
+        EsField field,
+        boolean synthetic
+    ) {
+        this(source, parentName, qualifier, name, field, Nullability.TRUE, null, synthetic);
     }
 
-    public FieldAttribute(Source source, @Nullable String parentName, String name, EsField field, boolean synthetic) {
-        this(source, parentName, name, field, Nullability.TRUE, null, synthetic);
+    public FieldAttribute(Source source, @Nullable String parentName, @Nullable String qualifier, String name, EsField field) {
+        this(source, parentName, qualifier, name, field, Nullability.TRUE, null, false);
     }
 
     public FieldAttribute(
         Source source,
         @Nullable String parentName,
+        @Nullable String qualifier,
         String name,
         EsField field,
         Nullability nullability,
         @Nullable NameId id,
         boolean synthetic
     ) {
-        super(source, name, field.getDataType(), nullability, id, synthetic);
+        super(source, qualifier, name, field.getDataType(), nullability, id, synthetic);
         this.parentName = parentName;
         this.field = field;
     }
@@ -92,6 +104,7 @@ private static FieldAttribute innerReadFrom(StreamInput in) throws IOException {
          */
         Source source = Source.readFrom((StreamInput & PlanStreamInput) in);
         String parentName = ((PlanStreamInput) in).readOptionalCachedString();
+        String qualifier = readQualifier((PlanStreamInput) in, in.getTransportVersion());
         String name = readCachedStringWithVersionCheck(in);
         if (in.getTransportVersion().before(ESQL_FIELD_ATTRIBUTE_DROP_TYPE)) {
             DataType.readFrom(in);
@@ -103,21 +116,22 @@ private static FieldAttribute innerReadFrom(StreamInput in) throws IOException {
         Nullability nullability = in.readEnum(Nullability.class);
         NameId nameId = NameId.readFrom((StreamInput & PlanStreamInput) in);
         boolean synthetic = in.readBoolean();
-        return new FieldAttribute(source, parentName, name, field, nullability, nameId, synthetic);
+        return new FieldAttribute(source, parentName, qualifier, name, field, nullability, nameId, synthetic);
     }
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         if (((PlanStreamOutput) out).writeAttributeCacheHeader(this)) {
             Source.EMPTY.writeTo(out);
             ((PlanStreamOutput) out).writeOptionalCachedString(parentName);
+            checkAndSerializeQualifier((PlanStreamOutput) out, out.getTransportVersion());
             writeCachedStringWithVersionCheck(out, name());
             if (out.getTransportVersion().before(ESQL_FIELD_ATTRIBUTE_DROP_TYPE)) {
                 dataType().writeTo(out);
             }
             field.writeTo(out);
             if (out.getTransportVersion().before(ESQL_FIELD_ATTRIBUTE_DROP_TYPE)) {
-                // We used to write the qualifier here. We can still do if needed in the future.
+                // We used to write the qualifier here, even though it was always null.
                 out.writeOptionalString(null);
             }
             out.writeEnum(nullable());
@@ -137,7 +151,7 @@ public String getWriteableName() {
 
     @Override
     protected NodeInfo<FieldAttribute> info() {
-        return NodeInfo.create(this, FieldAttribute::new, parentName, name(), field, nullable(), id(), synthetic());
+        return NodeInfo.create(this, FieldAttribute::new, parentName, qualifier(), name(), field, nullable(), id(), synthetic());
     }
 
     public String parentName() {
@@ -185,13 +199,30 @@ public FieldAttribute exactAttribute() {
     }
 
     private FieldAttribute innerField(EsField type) {
-        return new FieldAttribute(source(), fieldName().string, name() + "." + type.getName(), type, nullable(), id(), synthetic());
+        return new FieldAttribute(
+            source(),
+            fieldName().string,
+            qualifier(),
+            name() + "." + type.getName(),
+            type,
+            nullable(),
+            id(),
+            synthetic()
+        );
     }
 
     @Override
-    protected Attribute clone(Source source, String name, DataType type, Nullability nullability, NameId id, boolean synthetic) {
+    protected Attribute clone(
+        Source source,
+        String qualifier,
+        String name,
+        DataType type,
+        Nullability nullability,
+        NameId id,
+        boolean synthetic
+    ) {
         // Ignore `type`, this must be the same as the field's type.
-        return new FieldAttribute(source, parentName, name, field, nullability, id, synthetic);
+        return new FieldAttribute(source, parentName, qualifier, name, field, nullability, id, synthetic);
     }
 
     @Override

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/MetadataAttribute.java

@@ -111,7 +111,16 @@ public String getWriteableName() {
     }
 
     @Override
-    protected MetadataAttribute clone(Source source, String name, DataType type, Nullability nullability, NameId id, boolean synthetic) {
+    protected MetadataAttribute clone(
+        Source source,
+        String qualifier,
+        String name,
+        DataType type,
+        Nullability nullability,
+        NameId id,
+        boolean synthetic
+    ) {
+        // Ignores qualifier, as metadata attributes do not have qualifiers.
         return new MetadataAttribute(source, name, type, nullability, id, synthetic, searchable);
     }