ES|QL: Check if cluster aliases and index patterns are valid before executing query

docs/changelog/122497.yaml

@@ -0,0 +1,5 @@
+pr: 122497
+summary: Check if index patterns conform to valid format before validation
+area: CCS
+type: enhancement
+issues: []

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/parser/IdentifierBuilder.java

@@ -20,17 +20,20 @@
 import org.elasticsearch.xpack.esql.parser.EsqlBaseParser.IndexStringContext;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 import static org.elasticsearch.cluster.metadata.IndexNameExpressionResolver.SelectorResolver.SELECTOR_SEPARATOR;
 import static org.elasticsearch.transport.RemoteClusterAware.REMOTE_CLUSTER_INDEX_SEPARATOR;
-import static org.elasticsearch.transport.RemoteClusterAware.isRemoteIndexName;
+import static org.elasticsearch.transport.RemoteClusterAware.splitIndexName;
 import static org.elasticsearch.xpack.esql.core.util.StringUtils.EXCLUSION;
 import static org.elasticsearch.xpack.esql.core.util.StringUtils.WILDCARD;
 import static org.elasticsearch.xpack.esql.parser.ParserUtils.source;
 
 abstract class IdentifierBuilder extends AbstractBuilder {
 
+    private static final String BLANK_INDEX_ERROR_MESSAGE = "Blank index specified in index pattern";
+
     @Override
     public String visitIdentifier(IdentifierContext ctx) {
         return ctx == null ? null : unquoteIdentifier(ctx.QUOTED_IDENTIFIER(), ctx.UNQUOTED_IDENTIFIER());
@@ -88,39 +91,21 @@ public String visitIndexPattern(List<EsqlBaseParser.IndexPatternContext> ctx) {
             String indexPattern = c.unquotedIndexString() != null ? c.unquotedIndexString().getText() : visitIndexString(c.indexString());
             String clusterString = visitClusterString(c.clusterString());
             String selectorString = visitSelectorString(c.selectorString());
-            // skip validating index on remote cluster, because the behavior of remote cluster is not consistent with local cluster
-            // For example, invalid#index is an invalid index name, however FROM *:invalid#index does not return an error
-            if (clusterString == null) {
-                hasSeenStar.set(indexPattern.contains(WILDCARD) || hasSeenStar.get());
-                validateIndexPattern(indexPattern, c, hasSeenStar.get());
-                // Other instances of Elasticsearch may have differing selectors so only validate selector string if remote cluster
-                // string is unset
-                if (selectorString != null) {
-                    try {
-                        // Ensures that the selector provided is one of the valid kinds
-                        IndexNameExpressionResolver.SelectorResolver.validateIndexSelectorString(indexPattern, selectorString);
-                    } catch (InvalidIndexNameException e) {
-                        throw new ParsingException(e, source(c), e.getMessage());
-                    }
-                }
-            } else {
-                validateClusterString(clusterString, c);
-                // Do not allow selectors on remote cluster expressions until they are supported
-                if (selectorString != null) {
-                    throwOnMixingSelectorWithCluster(reassembleIndexName(clusterString, indexPattern, selectorString), c);
-                }
-            }
+
+            hasSeenStar.set(hasSeenStar.get() || indexPattern.contains(WILDCARD));
+            validate(clusterString, indexPattern, selectorString, c, hasSeenStar.get());
             patterns.add(reassembleIndexName(clusterString, indexPattern, selectorString));
         });
         return Strings.collectionToDelimitedString(patterns, ",");
     }
 
+    private static void throwInvalidIndexNameException(String indexPattern, String message, EsqlBaseParser.IndexPatternContext ctx) {
+        var ie = new InvalidIndexNameException(indexPattern, message);
+        throw new ParsingException(ie, source(ctx), ie.getMessage());
+    }
+
     private static void throwOnMixingSelectorWithCluster(String indexPattern, EsqlBaseParser.IndexPatternContext c) {
-        InvalidIndexNameException ie = new InvalidIndexNameException(
-            indexPattern,
-            "Selectors are not yet supported on remote cluster patterns"
-        );
-        throw new ParsingException(ie, source(c), ie.getMessage());
+        throwInvalidIndexNameException(indexPattern, "Selectors are not yet supported on remote cluster patterns", c);
     }
 
     private static String reassembleIndexName(String clusterString, String indexPattern, String selectorString) {
@@ -144,59 +129,196 @@ protected static void validateClusterString(String clusterString, EsqlBaseParser
         }
     }
 
-    private static void validateIndexPattern(String indexPattern, EsqlBaseParser.IndexPatternContext ctx, boolean hasSeenStar) {
-        // multiple index names can be in the same double quote, e.g. indexPattern = "idx1, *, -idx2"
-        String[] indices = indexPattern.split(",");
-        boolean hasExclusion = false;
-        for (String index : indices) {
-            // Strip spaces off first because validation checks are not written to handle them
-            index = index.strip();
-            if (isRemoteIndexName(index)) { // skip the validation if there is remote cluster
-                // Ensure that there are no selectors as they are not yet supported
-                if (index.contains(SELECTOR_SEPARATOR)) {
-                    throwOnMixingSelectorWithCluster(index, ctx);
-                }
-                continue;
+    /**
+     * Takes the parsed constituent strings and validates them.
+     * @param clusterString Name of the remote cluster. Can be null.
+     * @param indexPattern Name of the index or pattern; can also have multiple patterns in case of quoting,
+     *                     e.g. {@code FROM """index*,-index1"""}.
+     * @param selectorString Selector string, i.e. "::data" or "::failures". Can be null.
+     * @param ctx Index Pattern Context for generating error messages with offsets.
+     * @param hasSeenStar If we've seen an asterisk so far.
+     */
+    private static void validate(
+        String clusterString,
+        String indexPattern,
+        String selectorString,
+        EsqlBaseParser.IndexPatternContext ctx,
+        boolean hasSeenStar
+    ) {
+        /*
+         * At this point, only 3 formats are possible:
+         * "index_pattern(s)",
+         * remote:index_pattern, and,
+         * index_pattern::selector_string.
+         *
+         * The grammar prohibits remote:"index_pattern(s)" or "index_pattern(s)"::selector_string as they're
+         * partially quoted. So if either of cluster string or selector string are present, there's no need
+         * to split the pattern by comma since comma requires partial quoting.
+         */
+
+        String[] patterns;
+        if (clusterString == null && selectorString == null) {
+            // Pattern could be quoted or is singular like "index_name".
+            patterns = indexPattern.split(",", -1);
+        } else {
+            // Either of cluster string or selector string is present. Pattern is unquoted.
+            patterns = new String[] { indexPattern };
+        }
+
+        patterns = Arrays.stream(patterns).map(String::strip).toArray(String[]::new);
+        if (Arrays.stream(patterns).anyMatch(String::isBlank)) {
+            throwInvalidIndexNameException(indexPattern, BLANK_INDEX_ERROR_MESSAGE, ctx);
+        }
+
+        // Edge case: happens when all the index names in a pattern are empty like "FROM ",,,,,"".
+        if (patterns.length == 0) {
+            throwInvalidIndexNameException(indexPattern, BLANK_INDEX_ERROR_MESSAGE, ctx);
+        } else if (patterns.length == 1) {
+            // Pattern is either an unquoted string or a quoted string with a single index (no comma sep).
+            validateSingleIndexPattern(clusterString, patterns[0], selectorString, ctx, hasSeenStar);
+        } else {
+            /*
+             * Presence of multiple patterns requires a comma and comma requires quoting. If quoting is present,
+             * cluster string and selector string cannot be present; they need to be attached within the quoting.
+             * So we attempt to extract them later.
+             */
+            for (String pattern : patterns) {
+                validateSingleIndexPattern(null, pattern, null, ctx, hasSeenStar);
             }
+        }
+    }
+
+    /**
+     * Validates the constituent strings. Will extract the cluster string and/or selector string from the index
+     * name if clubbed together inside a quoted string.
+     *
+     * @param clusterString Name of the remote cluster. Can be null.
+     * @param indexName Name of the index.
+     * @param selectorString Selector string, i.e. "::data" or "::failures". Can be null.
+     * @param ctx Index Pattern Context for generating error messages with offsets.
+     * @param hasSeenStar If we've seen an asterisk so far.
+     */
+    private static void validateSingleIndexPattern(
+        String clusterString,
+        String indexName,
+        String selectorString,
+        EsqlBaseParser.IndexPatternContext ctx,
+        boolean hasSeenStar
+    ) {
+        indexName = indexName.strip();
+
+        /*
+         * Precedence:
+         * 1. Cannot mix cluster and selector strings.
+         * 2. Cluster string must be valid.
+         * 3. Index name must be valid.
+         * 4. Selector string must be valid.
+         *
+         * Since cluster string and/or selector string can be clubbed with the index name, we must try to
+         * manually extract them before we attempt to do #2, #3, and #4.
+         */
+
+        // It is possible to specify a pattern like "remote_cluster:index_name". Try to extract such details from the index string.
+        if (clusterString == null && selectorString == null) {
             try {
-                Tuple<String, String> splitPattern = IndexNameExpressionResolver.splitSelectorExpression(index);
-                if (splitPattern.v2() != null) {
-                    index = splitPattern.v1();
-                }
-            } catch (InvalidIndexNameException e) {
-                // throws exception if the selector expression is invalid. Selector resolution does not complain about exclusions
+                var split = splitIndexName(indexName);
+                clusterString = split[0];
+                indexName = split[1];
+            } catch (IllegalArgumentException e) {
                 throw new ParsingException(e, source(ctx), e.getMessage());
             }
-            hasSeenStar = index.contains(WILDCARD) || hasSeenStar;
-            index = index.replace(WILDCARD, "").strip();
-            if (index.isBlank()) {
-                continue;
-            }
-            hasExclusion = index.startsWith(EXCLUSION);
-            index = removeExclusion(index);
-            String tempName;
-            try {
-                // remove the exclusion outside of <>, from index names with DateMath expression,
-                // e.g. -<-logstash-{now/d}> becomes <-logstash-{now/d}> before calling resolveDateMathExpression
-                tempName = IndexNameExpressionResolver.resolveDateMathExpression(index);
-            } catch (ElasticsearchParseException e) {
-                // throws exception if the DateMath expression is invalid, resolveDateMathExpression does not complain about exclusions
-                throw new ParsingException(e, source(ctx), e.getMessage());
+        }
+
+        // At the moment, selector strings for remote indices is not allowed.
+        if (clusterString != null && selectorString != null) {
+            throwOnMixingSelectorWithCluster(reassembleIndexName(clusterString, indexName, selectorString), ctx);
+        }
+
+        // Validation in the right precedence.
+        if (clusterString != null) {
+            clusterString = clusterString.strip();
+            validateClusterString(clusterString, ctx);
+        }
+
+        /*
+         * It is possible for selector string to be attached to the index: "index_name::selector_string".
+         * Try to extract the selector string.
+         */
+        try {
+            Tuple<String, String> splitPattern = IndexNameExpressionResolver.splitSelectorExpression(indexName);
+            if (splitPattern.v2() != null) {
+                // Cluster string too was clubbed with the index name like selector string.
+                if (clusterString != null) {
+                    throwOnMixingSelectorWithCluster(reassembleIndexName(clusterString, splitPattern.v1(), splitPattern.v2()), ctx);
+                } else {
+                    // We've seen a selectorString. Use it.
+                    selectorString = splitPattern.v2();
+                }
             }
-            hasExclusion = tempName.startsWith(EXCLUSION) || hasExclusion;
-            index = tempName.equals(index) ? index : removeExclusion(tempName);
+
+            indexName = splitPattern.v1();
+        } catch (InvalidIndexNameException e) {
+            throw new ParsingException(e, source(ctx), e.getMessage());
+        }
+
+        resolveAndValidateIndex(indexName, ctx, hasSeenStar);
+        if (selectorString != null) {
+            selectorString = selectorString.strip();
             try {
-                MetadataCreateIndexService.validateIndexOrAliasName(index, InvalidIndexNameException::new);
+                // Ensures that the selector provided is one of the valid kinds.
+                IndexNameExpressionResolver.SelectorResolver.validateIndexSelectorString(indexName, selectorString);
             } catch (InvalidIndexNameException e) {
-                // ignore invalid index name if it has exclusions and there is an index with wildcard before it
-                if (hasSeenStar && hasExclusion) {
-                    continue;
-                }
                 throw new ParsingException(e, source(ctx), e.getMessage());
             }
         }
     }
 
+    private static void resolveAndValidateIndex(String index, EsqlBaseParser.IndexPatternContext ctx, boolean hasSeenStar) {
+        // If index name is blank without any replacements, it was likely blank right from the beginning and is invalid.
+        if (index.isBlank()) {
+            throwInvalidIndexNameException(index, BLANK_INDEX_ERROR_MESSAGE, ctx);
+        }
+
+        hasSeenStar = hasSeenStar || index.contains(WILDCARD);
+        index = index.replace(WILDCARD, "").strip();
+        if (index.isBlank()) {
+            return;
+        }
+        var hasExclusion = index.startsWith(EXCLUSION);
+        index = removeExclusion(index);
+        String tempName;
+        try {
+            // remove the exclusion outside of <>, from index names with DateMath expression,
+            // e.g. -<-logstash-{now/d}> becomes <-logstash-{now/d}> before calling resolveDateMathExpression
+            tempName = IndexNameExpressionResolver.resolveDateMathExpression(index);
+        } catch (ElasticsearchParseException e) {
+            // throws exception if the DateMath expression is invalid, resolveDateMathExpression does not complain about exclusions
+            throw new ParsingException(e, source(ctx), e.getMessage());
+        }
+        hasExclusion = tempName.startsWith(EXCLUSION) || hasExclusion;
+        index = tempName.equals(index) ? index : removeExclusion(tempName);
+        try {
+            MetadataCreateIndexService.validateIndexOrAliasName(index, InvalidIndexNameException::new);
+        } catch (InvalidIndexNameException e) {
+            // ignore invalid index name if it has exclusions and there is an index with wildcard before it
+            if (hasSeenStar && hasExclusion) {
+                return;
+            }
+
+            InvalidIndexNameException errorToThrow = e;
+            /*
+             * We only modify this particular message because it mentions '*' as an invalid char.
+             * However, we do allow asterisk in the index patterns: wildcarded patterns. Let's not
+             * mislead the user by mentioning this char in the error message.
+             */
+            if (e.getMessage().contains("must not contain the following characters")) {
+                errorToThrow = new InvalidIndexNameException(index, e.getMessage().replace("'*',", ""));
+            }
+
+            throw new ParsingException(errorToThrow, source(ctx), errorToThrow.getMessage());
+        }
+    }
+
     private static String removeExclusion(String indexPattern) {
         return indexPattern.charAt(0) == EXCLUSION.charAt(0) ? indexPattern.substring(1) : indexPattern;
     }