Support types table in lookup join docs

docs/reference/query-languages/esql/_snippets/commands/layout/lookup-join.md

@@ -42,6 +42,9 @@ results, the output will contain one row for each matching combination.
 For important information about using `LOOKUP JOIN`, refer to [Usage notes](../../../../esql/esql-lookup-join.md#usage-notes).
 ::::
 
+:::{include} ../types/lookup-join.md
+:::
+
 **Examples**
 
 **IP Threat correlation**: This query would allow you to see if any source

docs/reference/query-languages/esql/_snippets/commands/types/lookup-join.md

@@ -0,0 +1,77 @@
+% This is generated by ESQL's AbstractFunctionTestCase. Do not edit it. See ../README.md for how to regenerate it.
+
+**Supported types**
+
+| main | join | 
+| --- | --- | 
+| boolean | boolean | 
+| byte | byte | 
+| byte | double | 
+| byte | float | 
+| byte | half_float | 
+| byte | integer | 
+| byte | long | 
+| byte | scaled_float | 
+| byte | short | 
+| date | date | 
+| date_nanos | date_nanos | 
+| double | byte | 
+| double | double | 
+| double | float | 
+| double | half_float | 
+| double | integer | 
+| double | long | 
+| double | scaled_float | 
+| double | short | 
+| float | byte | 
+| float | double | 
+| float | float | 
+| float | half_float | 
+| float | integer | 
+| float | long | 
+| float | scaled_float | 
+| float | short | 
+| half_float | byte | 
+| half_float | double | 
+| half_float | float | 
+| half_float | half_float | 
+| half_float | integer | 
+| half_float | long | 
+| half_float | scaled_float | 
+| half_float | short | 
+| integer | byte | 
+| integer | double | 
+| integer | float | 
+| integer | half_float | 
+| integer | integer | 
+| integer | long | 
+| integer | scaled_float | 
+| integer | short | 
+| ip | ip | 
+| keyword | keyword | 
+| long | byte | 
+| long | double | 
+| long | float | 
+| long | half_float | 
+| long | integer | 
+| long | long | 
+| long | scaled_float | 
+| long | short | 
+| scaled_float | byte | 
+| scaled_float | double | 
+| scaled_float | float | 
+| scaled_float | half_float | 
+| scaled_float | integer | 
+| scaled_float | long | 
+| scaled_float | scaled_float | 
+| scaled_float | short | 
+| short | byte | 
+| short | double | 
+| short | float | 
+| short | half_float | 
+| short | integer | 
+| short | long | 
+| short | scaled_float | 
+| short | short | 
+| text | keyword | 
+

docs/reference/query-languages/esql/esql-lookup-join.md

@@ -151,10 +151,15 @@
     * `short` and `byte` are compatible with `integer` (all represented as `int`)
     * `float`, `half_float`, and `scaled_float` are compatible with `double` (all represented as `double`)
   * For text fields: You can only use text fields as the join key on the left-hand side of the join and only if they have a `.keyword` subfield
+  * `DATE` and `DATE_NANOS` can only be joined against the exact same type.
 
 To obtain a join key with a compatible type, use a [conversion function](/reference/query-languages/esql/functions-operators/type-conversion-functions.md) if needed.
 
-For a complete list of supported data types and their internal representations, see the [Supported Field Types documentation](/reference/query-languages/esql/limitations.md#_supported_types).
+The list of unsupported fields includes all types not supported by {{esql}} as described in the [Unsupported Field Types documentation](/reference/query-languages/esql/limitations.md#_unsupported_types).
+as well as the following: `VERSION`, `UNSIGNED_LONG`, all spatial types like `GEO_POINT`, `GEO_SHAPE`, and all
+temporal periods like `DURATION` and `PERIOD`.
+
+For a complete list of all types supported in `LOOKUP JOIN`, refer to the [`LOOKUP JOIN` supported types table](/reference/query-languages/esql/commands/processing-commands#esql-lookup-join).
 
 ## Usage notes
 

x-pack/plugin/esql/build.gradle

@@ -226,6 +226,45 @@ tasks.named("test").configure {
   }
 }
 
+tasks.named("internalClusterTest").configure {
+  if (buildParams.ci == false) {
+    systemProperty 'generateDocs', true
+    def injected = project.objects.newInstance(Injected)
+    // Define the folder to delete and recreate
+    def tempDir = file("build/testrun/internalClusterTest/temp/esql")
+    doFirst {
+      injected.fs.delete {
+        it.delete(tempDir)
+      }
+      // Re-create this folder so we can save a table of generated examples to extract from csv-spec tests
+      tempDir.mkdirs() // Recreate the folder
+    }
+    File snippetsFolder = file("build/testrun/internalClusterTest/temp/esql/_snippets")
+    def snippetsDocFolder = file("${rootDir}/docs/reference/query-languages/esql/_snippets")
+    def snippetsTree = fileTree(snippetsFolder).matching {
+      include "**/types/*.md"  // Recursively include all types/*.md files (effectively counting functions and operators)
+    }
+
+    doLast {
+      def snippets = snippetsTree.files.collect { it.name }
+      int countSnippets = snippets.size()
+      if (countSnippets == 0) {
+        logger.quiet("ESQL Docs: No function/operator snippets created. Skipping sync.")
+      } else {
+        logger.quiet("ESQL Docs: Found $countSnippets generated function/operator snippets to patch into docs")
+        injected.fs.sync {
+          from snippetsFolder
+          into snippetsDocFolder
+          include '**/*.md'
+          preserve {
+            include '**/*.md'
+          }
+        }
+      }
+    }
+  }
+}
+
 /****************************************************************
  *  Enable QA/rest integration tests for snapshot builds only   *
  *  TODO: Enable for all builds upon this feature release       *

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

@@ -19,6 +19,8 @@
 import org.elasticsearch.xpack.core.esql.action.ColumnInfo;
 import org.elasticsearch.xpack.esql.VerificationException;
 import org.elasticsearch.xpack.esql.core.type.DataType;
+import org.elasticsearch.xpack.esql.expression.function.DocsV3Support;
+import org.elasticsearch.xpack.esql.expression.function.EsqlFunctionRegistry;
 import org.elasticsearch.xpack.esql.plan.logical.join.Join;
 import org.elasticsearch.xpack.esql.plugin.EsqlPlugin;
 import org.elasticsearch.xpack.spatial.SpatialPlugin;
@@ -36,6 +38,7 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.function.Consumer;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 import static org.elasticsearch.test.ESIntegTestCase.Scope.SUITE;
@@ -265,6 +268,21 @@ private static boolean existingIndex(Collection<TestConfigs> existing, DataType
         return existing.stream().anyMatch(c -> c.exists(indexName));
     }
 
+    public void testOutputSupportedTypes() throws Exception {
+        Map<List<DataType>, DataType> signatures = new LinkedHashMap<>();
+        for (TestConfigs configs : testConfigurations.values()) {
+            if (configs.group.equals("unsupported") || configs.group.equals("union-types")) {
+                continue;
+            }
+            for (TestConfig config : configs.configs.values()) {
+                if (config instanceof TestConfigPasses) {
+                    signatures.put(List.of(config.mainType(), config.lookupType()), null);
+                }
+            }
+        }
+        saveJoinTypes(() -> signatures);
+    }
+
     public void testLookupJoinStrings() {
         testLookupJoinTypes("strings");
     }
@@ -747,4 +765,18 @@ public void doTest() {
     private boolean isValidDataType(DataType dataType) {
         return UNDER_CONSTRUCTION.get(dataType) == null || UNDER_CONSTRUCTION.get(dataType).isEnabled();
     }
+
+    private static void saveJoinTypes(Supplier<Map<List<DataType>, DataType>> signatures) throws Exception {
+        ArrayList<EsqlFunctionRegistry.ArgSignature> args = new ArrayList<>();
+        args.add(new EsqlFunctionRegistry.ArgSignature("main", null, "Field from the main index", false, false));
+        args.add(new EsqlFunctionRegistry.ArgSignature("join", null, "Field from the join index", false, false));
+        DocsV3Support.CommandsDocsSupport docs = new DocsV3Support.CommandsDocsSupport(
+            "lookup-join",
+            LookupJoinTypesIT.class,
+            null,
+            args,
+            signatures
+        );
+        docs.renderDocs();
+    }
 }

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/function/DocsV3Support.java

@@ -62,6 +62,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.function.Function;
 import java.util.function.Supplier;
@@ -859,9 +860,11 @@ private ObservabilityTier getObservabilityTier() {
     /** Command specific docs generating, currently very empty since we only render kibana definition files */
     public static class CommandsDocsSupport extends DocsV3Support {
         private final LogicalPlan command;
+        private List<EsqlFunctionRegistry.ArgSignature> args;
         private final XPackLicenseState licenseState;
         private final ObservabilityTier observabilityTier;
 
+        /** Used in CommandLicenseTests to generate Kibana docs with licensing information for commands */
         public CommandsDocsSupport(
             String name,
             Class<?> testClass,
@@ -875,15 +878,36 @@ public CommandsDocsSupport(
             this.observabilityTier = observabilityTier;
         }
 
+        /** Used in LookupJoinTypesIT to generate table of supported types for join field */
+        public CommandsDocsSupport(
+            String name,
+            Class<?> testClass,
+            LogicalPlan command,
+            List<EsqlFunctionRegistry.ArgSignature> args,
+            Supplier<Map<List<DataType>, DataType>> signatures
+        ) {
+            super("commands", name, testClass, signatures);
+            this.command = command;
+            this.args = args;
+            this.licenseState = null;
+            this.observabilityTier = null;
+        }
+
         @Override
         public void renderSignature() throws IOException {
             // Unimplemented until we make command docs dynamically generated
         }
 
         @Override
         public void renderDocs() throws Exception {
-            // Currently we only render kibana definition files, but we could expand to rendering much more if we decide to
-            renderKibanaCommandDefinition();
+            // Currently we only render either signatures or kibana definition files,
+            // but we could expand to rendering much more if we decide to
+            if (args != null) {
+                renderTypes(name, args);
+            }
+            if (licenseState != null) {
+                renderKibanaCommandDefinition();
+            }
         }
 
         void renderKibanaCommandDefinition() throws Exception {
@@ -927,15 +951,18 @@ void renderParametersList(List<String> argNames, List<String> argDescriptions) t
     }
 
     void renderTypes(String name, List<EsqlFunctionRegistry.ArgSignature> args) throws IOException {
+        boolean showResultColumn = signatures.get().values().stream().anyMatch(Objects::nonNull);
         StringBuilder header = new StringBuilder("| ");
         StringBuilder separator = new StringBuilder("| ");
         List<String> argNames = args.stream().map(EsqlFunctionRegistry.ArgSignature::name).toList();
         for (String arg : argNames) {
             header.append(arg).append(" | ");
             separator.append("---").append(" | ");
         }
-        header.append("result |");
-        separator.append("--- |");
+        if (showResultColumn) {
+            header.append("result |");
+            separator.append("--- |");
+        }
 
         List<String> table = new ArrayList<>();
         for (Map.Entry<List<DataType>, DataType> sig : this.signatures.get().entrySet()) { // TODO flip to using sortedSignatures
@@ -945,7 +972,7 @@ void renderTypes(String name, List<EsqlFunctionRegistry.ArgSignature> args) thro
             if (sig.getKey().size() > argNames.size()) { // skip variadic [test] cases (but not those with optional parameters)
                 continue;
             }
-            table.add(getTypeRow(args, sig, argNames));
+            table.add(getTypeRow(args, sig, argNames, showResultColumn));
         }
         Collections.sort(table);
         if (table.isEmpty()) {
@@ -964,7 +991,8 @@ void renderTypes(String name, List<EsqlFunctionRegistry.ArgSignature> args) thro
     private static String getTypeRow(
         List<EsqlFunctionRegistry.ArgSignature> args,
         Map.Entry<List<DataType>, DataType> sig,
-        List<String> argNames
+        List<String> argNames,
+        boolean showResultColumn
     ) {
         StringBuilder b = new StringBuilder("| ");
         for (int i = 0; i < sig.getKey().size(); i++) {
@@ -978,8 +1006,10 @@ private static String getTypeRow(
             b.append(" | ");
         }
         b.append("| ".repeat(argNames.size() - sig.getKey().size()));
-        b.append(sig.getValue().esNameIfPossible());
-        b.append(" |");
+        if (showResultColumn) {
+            b.append(sig.getValue().esNameIfPossible());
+            b.append(" |");
+        }
         return b.toString();
     }