support in compound queries / filter parsers for lower level ones returning null as the result of parsing the inner query / filter.

src/main/java/org/elasticsearch/common/lucene/search/Queries.java

@@ -33,6 +33,7 @@ public class Queries {
 
     // We don't use MatchAllDocsQuery, its slower than the one below ... (much slower)
     public final static Query MATCH_ALL_QUERY = new DeletionAwareConstantScoreQuery(new MatchAllDocsFilter());
+    public final static Query NO_MATCH_QUERY = MatchNoDocsQuery.INSTANCE;
 
     /**
      * A match all docs filter. Note, requires no caching!.

src/main/java/org/elasticsearch/index/query/AndFilterParser.java

@@ -51,6 +51,7 @@ public class AndFilterParser implements FilterParser {
         XContentParser parser = parseContext.parser();
 
         ArrayList<Filter> filters = newArrayList();
+        boolean filtersFound = false;
 
         boolean cache = false;
         CacheKeyFilter.Key cacheKey = null;
@@ -60,7 +61,11 @@ public class AndFilterParser implements FilterParser {
         XContentParser.Token token = parser.currentToken();
         if (token == XContentParser.Token.START_ARRAY) {
             while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                filters.add(parseContext.parseInnerFilter());
+                filtersFound = true;
+                Filter filter = parseContext.parseInnerFilter();
+                if (filter != null) {
+                    filters.add(filter);
+                }
             }
         } else {
             while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
@@ -68,12 +73,20 @@ public class AndFilterParser implements FilterParser {
                     currentFieldName = parser.currentName();
                 } else if (token == XContentParser.Token.START_ARRAY) {
                     if ("filters".equals(currentFieldName)) {
+                        filtersFound = true;
                         while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                            filters.add(parseContext.parseInnerFilter());
+                            Filter filter = parseContext.parseInnerFilter();
+                            if (filter != null) {
+                                filters.add(filter);
+                            }
                         }
                     } else {
+                        filtersFound = true;
                         while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                            filters.add(parseContext.parseInnerFilter());
+                            Filter filter = parseContext.parseInnerFilter();
+                            if (filter != null) {
+                                filters.add(filter);
+                            }
                         }
                     }
                 } else if (token.isValue()) {
@@ -90,10 +103,14 @@ public class AndFilterParser implements FilterParser {
             }
         }
 
-        if (filters.isEmpty()) {
+        if (!filtersFound) {
             throw new QueryParsingException(parseContext.index(), "[and] filter requires 'filters' to be set on it'");
         }
 
+        if (filters.isEmpty()) {
+            return null;
+        }
+
         // no need to cache this one
         Filter filter = new AndFilter(filters);
         if (cache) {

src/main/java/org/elasticsearch/index/query/BoolFilterParser.java

@@ -62,26 +62,44 @@ public class BoolFilterParser implements FilterParser {
                 currentFieldName = parser.currentName();
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("must".equals(currentFieldName)) {
-                    boolFilter.add(new FilterClause(parseContext.parseInnerFilter(), BooleanClause.Occur.MUST));
+                    Filter filter = parseContext.parseInnerFilter();
+                    if (filter != null) {
+                        boolFilter.add(new FilterClause(filter, BooleanClause.Occur.MUST));
+                    }
                 } else if ("must_not".equals(currentFieldName) || "mustNot".equals(currentFieldName)) {
-                    boolFilter.add(new FilterClause(parseContext.parseInnerFilter(), BooleanClause.Occur.MUST_NOT));
+                    Filter filter = parseContext.parseInnerFilter();
+                    if (filter != null) {
+                        boolFilter.add(new FilterClause(filter, BooleanClause.Occur.MUST_NOT));
+                    }
                 } else if ("should".equals(currentFieldName)) {
-                    boolFilter.add(new FilterClause(parseContext.parseInnerFilter(), BooleanClause.Occur.SHOULD));
+                    Filter filter = parseContext.parseInnerFilter();
+                    if (filter != null) {
+                        boolFilter.add(new FilterClause(filter, BooleanClause.Occur.SHOULD));
+                    }
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[bool] filter does not support [" + currentFieldName + "]");
                 }
             } else if (token == XContentParser.Token.START_ARRAY) {
                 if ("must".equals(currentFieldName)) {
                     while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                        boolFilter.add(new FilterClause(parseContext.parseInnerFilter(), BooleanClause.Occur.MUST));
+                        Filter filter = parseContext.parseInnerFilter();
+                        if (filter != null) {
+                            boolFilter.add(new FilterClause(filter, BooleanClause.Occur.MUST));
+                        }
                     }
                 } else if ("must_not".equals(currentFieldName) || "mustNot".equals(currentFieldName)) {
                     while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                        boolFilter.add(new FilterClause(parseContext.parseInnerFilter(), BooleanClause.Occur.MUST_NOT));
+                        Filter filter = parseContext.parseInnerFilter();
+                        if (filter != null) {
+                            boolFilter.add(new FilterClause(filter, BooleanClause.Occur.MUST_NOT));
+                        }
                     }
                 } else if ("should".equals(currentFieldName)) {
                     while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                        boolFilter.add(new FilterClause(parseContext.parseInnerFilter(), BooleanClause.Occur.SHOULD));
+                        Filter filter = parseContext.parseInnerFilter();
+                        if (filter != null) {
+                            boolFilter.add(new FilterClause(filter, BooleanClause.Occur.SHOULD));
+                        }
                     }
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[bool] filter does not support [" + currentFieldName + "]");
@@ -99,6 +117,10 @@ public class BoolFilterParser implements FilterParser {
             }
         }
 
+        if (boolFilter.getMustFilters().isEmpty() && boolFilter.getNotFilters().isEmpty() && boolFilter.getShouldFilters().isEmpty()) {
+            return null;
+        }
+
         Filter filter = boolFilter;
         if (cache) {
             filter = parseContext.cacheFilter(filter, cacheKey);

src/main/java/org/elasticsearch/index/query/BoolQueryParser.java

@@ -67,26 +67,44 @@ public class BoolQueryParser implements QueryParser {
                 currentFieldName = parser.currentName();
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("must".equals(currentFieldName)) {
-                    clauses.add(new BooleanClause(parseContext.parseInnerQuery(), BooleanClause.Occur.MUST));
+                    Query query = parseContext.parseInnerQuery();
+                    if (query != null) {
+                        clauses.add(new BooleanClause(query, BooleanClause.Occur.MUST));
+                    }
                 } else if ("must_not".equals(currentFieldName) || "mustNot".equals(currentFieldName)) {
-                    clauses.add(new BooleanClause(parseContext.parseInnerQuery(), BooleanClause.Occur.MUST_NOT));
+                    Query query = parseContext.parseInnerQuery();
+                    if (query != null) {
+                        clauses.add(new BooleanClause(query, BooleanClause.Occur.MUST_NOT));
+                    }
                 } else if ("should".equals(currentFieldName)) {
-                    clauses.add(new BooleanClause(parseContext.parseInnerQuery(), BooleanClause.Occur.SHOULD));
+                    Query query = parseContext.parseInnerQuery();
+                    if (query != null) {
+                        clauses.add(new BooleanClause(query, BooleanClause.Occur.SHOULD));
+                    }
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[bool] query does not support [" + currentFieldName + "]");
                 }
             } else if (token == XContentParser.Token.START_ARRAY) {
                 if ("must".equals(currentFieldName)) {
                     while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                        clauses.add(new BooleanClause(parseContext.parseInnerQuery(), BooleanClause.Occur.MUST));
+                        Query query = parseContext.parseInnerQuery();
+                        if (query != null) {
+                            clauses.add(new BooleanClause(query, BooleanClause.Occur.MUST));
+                        }
                     }
                 } else if ("must_not".equals(currentFieldName) || "mustNot".equals(currentFieldName)) {
                     while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                        clauses.add(new BooleanClause(parseContext.parseInnerQuery(), BooleanClause.Occur.MUST_NOT));
+                        Query query = parseContext.parseInnerQuery();
+                        if (query != null) {
+                            clauses.add(new BooleanClause(query, BooleanClause.Occur.MUST_NOT));
+                        }
                     }
                 } else if ("should".equals(currentFieldName)) {
                     while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                        clauses.add(new BooleanClause(parseContext.parseInnerQuery(), BooleanClause.Occur.SHOULD));
+                        Query query = parseContext.parseInnerQuery();
+                        if (query != null) {
+                            clauses.add(new BooleanClause(query, BooleanClause.Occur.SHOULD));
+                        }
                     }
                 } else {
                     throw new QueryParsingException(parseContext.index(), "bool query does not support [" + currentFieldName + "]");
@@ -106,6 +124,10 @@ public class BoolQueryParser implements QueryParser {
             }
         }
 
+        if (clauses.isEmpty()) {
+            return null;
+        }
+
         if (clauses.size() == 1) {
             BooleanClause clause = clauses.get(0);
             if (clause.getOccur() == BooleanClause.Occur.MUST) {

src/main/java/org/elasticsearch/index/query/BoostingQueryParser.java

@@ -47,7 +47,9 @@ public class BoostingQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query positiveQuery = null;
+        boolean positiveQueryFound = false;
         Query negativeQuery = null;
+        boolean negativeQueryFound = false;
         float boost = -1;
         float negativeBoost = -1;
 
@@ -59,8 +61,10 @@ public class BoostingQueryParser implements QueryParser {
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("positive".equals(currentFieldName)) {
                     positiveQuery = parseContext.parseInnerQuery();
+                    positiveQueryFound = true;
                 } else if ("negative".equals(currentFieldName)) {
                     negativeQuery = parseContext.parseInnerQuery();
+                    negativeQueryFound = true;
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[boosting] query does not support [" + currentFieldName + "]");
                 }
@@ -75,16 +79,21 @@ public class BoostingQueryParser implements QueryParser {
             }
         }
 
-        if (positiveQuery == null) {
+        if (positiveQuery == null && !positiveQueryFound) {
             throw new QueryParsingException(parseContext.index(), "[boosting] query requires 'positive' query to be set'");
         }
-        if (negativeQuery == null) {
+        if (negativeQuery == null && !negativeQueryFound) {
             throw new QueryParsingException(parseContext.index(), "[boosting] query requires 'negative' query to be set'");
         }
         if (negativeBoost == -1) {
             throw new QueryParsingException(parseContext.index(), "[boosting] query requires 'negative_boost' to be set'");
         }
 
+        // parsers returned null
+        if (positiveQuery == null || negativeQuery == null) {
+            return null;
+        }
+
         BoostingQuery boostingQuery = new BoostingQuery(positiveQuery, negativeQuery, negativeBoost);
         if (boost != -1) {
             boostingQuery.setBoost(boost);

src/main/java/org/elasticsearch/index/query/ConstantScoreQueryParser.java

@@ -51,7 +51,9 @@ public class ConstantScoreQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Filter filter = null;
+        boolean filterFound = false;
         Query query = null;
+        boolean queryFound = false;
         float boost = 1.0f;
         boolean cache = false;
         CacheKeyFilter.Key cacheKey = null;
@@ -64,8 +66,10 @@ public class ConstantScoreQueryParser implements QueryParser {
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("filter".equals(currentFieldName)) {
                     filter = parseContext.parseInnerFilter();
+                    filterFound = true;
                 } else if ("query".equals(currentFieldName)) {
                     query = parseContext.parseInnerQuery();
+                    queryFound = true;
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[constant_score] query does not support [" + currentFieldName + "]");
                 }
@@ -81,10 +85,14 @@ public class ConstantScoreQueryParser implements QueryParser {
                 }
             }
         }
-        if (filter == null && query == null) {
+        if (!filterFound && !queryFound) {
             throw new QueryParsingException(parseContext.index(), "[constant_score] requires either 'filter' or 'query' element");
         }
 
+        if (query == null && filter == null) {
+            return null;
+        }
+
         if (filter != null) {
             // cache the filter if possible needed
             if (cache) {

src/main/java/org/elasticsearch/index/query/CustomBoostFactorQueryParser.java

@@ -49,6 +49,7 @@ public class CustomBoostFactorQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         float boost = 1.0f;
         float boostFactor = 1.0f;
 
@@ -60,6 +61,7 @@ public class CustomBoostFactorQueryParser implements QueryParser {
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("query".equals(currentFieldName)) {
                     query = parseContext.parseInnerQuery();
+                    queryFound = true;
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[custom_boost_factor] query does not support [" + currentFieldName + "]");
                 }
@@ -73,9 +75,12 @@ public class CustomBoostFactorQueryParser implements QueryParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[constant_factor_query] requires 'query' element");
         }
+        if (query == null) {
+            return null;
+        }
         FunctionScoreQuery functionScoreQuery = new FunctionScoreQuery(query, new BoostScoreFunction(boostFactor));
         functionScoreQuery.setBoost(boost);
         return functionScoreQuery;

src/main/java/org/elasticsearch/index/query/CustomFiltersScoreQueryParser.java

@@ -55,12 +55,14 @@ public class CustomFiltersScoreQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         float boost = 1.0f;
         String scriptLang = null;
         Map<String, Object> vars = null;
 
         FiltersFunctionScoreQuery.ScoreMode scoreMode = FiltersFunctionScoreQuery.ScoreMode.First;
         ArrayList<Filter> filters = new ArrayList<Filter>();
+        boolean filtersFound = false;
         ArrayList<String> scripts = new ArrayList<String>();
         TFloatArrayList boosts = new TFloatArrayList();
 
@@ -72,6 +74,7 @@ public class CustomFiltersScoreQueryParser implements QueryParser {
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("query".equals(currentFieldName)) {
                     query = parseContext.parseInnerQuery();
+                    queryFound = true;
                 } else if ("params".equals(currentFieldName)) {
                     vars = parser.map();
                 } else {
@@ -79,9 +82,11 @@ public class CustomFiltersScoreQueryParser implements QueryParser {
                 }
             } else if (token == XContentParser.Token.START_ARRAY) {
                 if ("filters".equals(currentFieldName)) {
+                    filtersFound = true;
                     while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
                         String script = null;
                         Filter filter = null;
+                        boolean filterFound = false;
                         float fboost = Float.NaN;
                         while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
                             if (token == XContentParser.Token.FIELD_NAME) {
@@ -89,6 +94,7 @@ public class CustomFiltersScoreQueryParser implements QueryParser {
                             } else if (token == XContentParser.Token.START_OBJECT) {
                                 if ("filter".equals(currentFieldName)) {
                                     filter = parseContext.parseInnerFilter();
+                                    filterFound = true;
                                 }
                             } else if (token.isValue()) {
                                 if ("script".equals(currentFieldName)) {
@@ -101,13 +107,15 @@ public class CustomFiltersScoreQueryParser implements QueryParser {
                         if (script == null && fboost == -1) {
                             throw new QueryParsingException(parseContext.index(), "[custom_filters_score] missing 'script' or 'boost' in filters array element");
                         }
-                        if (filter == null) {
+                        if (!filterFound) {
                             throw new QueryParsingException(parseContext.index(), "[custom_filters_score] missing 'filter' in filters array element");
                         }
+                        if (filter != null) {
                             filters.add(filter);
                             scripts.add(script);
                             boosts.add(fboost);
                         }
+                    }
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[custom_filters_score] query does not support [" + currentFieldName + "]");
                 }
@@ -138,12 +146,19 @@ public class CustomFiltersScoreQueryParser implements QueryParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[custom_filters_score] requires 'query' field");
         }
-        if (filters.isEmpty()) {
+        if (query == null) {
+            return null;
+        }
+        if (!filtersFound) {
             throw new QueryParsingException(parseContext.index(), "[custom_filters_score] requires 'filters' field");
         }
+        // if all filter elements returned null, just use the query
+        if (filters.isEmpty()) {
+            return query;
+        }
 
         FiltersFunctionScoreQuery.FilterFunction[] filterFunctions = new FiltersFunctionScoreQuery.FilterFunction[filters.size()];
         for (int i = 0; i < filterFunctions.length; i++) {

src/main/java/org/elasticsearch/index/query/CustomScoreQueryParser.java

@@ -53,6 +53,7 @@ public class CustomScoreQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         float boost = 1.0f;
         String script = null;
         String scriptLang = null;
@@ -66,6 +67,7 @@ public class CustomScoreQueryParser implements QueryParser {
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("query".equals(currentFieldName)) {
                     query = parseContext.parseInnerQuery();
+                    queryFound = true;
                 } else if ("params".equals(currentFieldName)) {
                     vars = parser.map();
                 } else {
@@ -83,12 +85,15 @@ public class CustomScoreQueryParser implements QueryParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[custom_score] requires 'query' field");
         }
         if (script == null) {
             throw new QueryParsingException(parseContext.index(), "[custom_score] requires 'script' field");
         }
+        if (query == null) {
+            return null;
+        }
 
         SearchScript searchScript = parseContext.scriptService().search(parseContext.lookup(), scriptLang, script, vars);
         FunctionScoreQuery functionScoreQuery = new FunctionScoreQuery(query, new ScriptScoreFunction(script, vars, searchScript));

src/main/java/org/elasticsearch/index/query/DisMaxQueryParser.java

@@ -54,6 +54,7 @@ public class DisMaxQueryParser implements QueryParser {
         float tieBreaker = 0.0f;
 
         List<Query> queries = newArrayList();
+        boolean queriesFound = false;
 
         String currentFieldName = null;
         XContentParser.Token token;
@@ -62,14 +63,22 @@ public class DisMaxQueryParser implements QueryParser {
                 currentFieldName = parser.currentName();
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("queries".equals(currentFieldName)) {
-                    queries.add(parseContext.parseInnerQuery());
+                    queriesFound = true;
+                    Query query = parseContext.parseInnerQuery();
+                    if (query != null) {
+                        queries.add(query);
+                    }
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[dis_max] query does not support [" + currentFieldName + "]");
                 }
             } else if (token == XContentParser.Token.START_ARRAY) {
                 if ("queries".equals(currentFieldName)) {
+                    queriesFound = true;
                     while (token != XContentParser.Token.END_ARRAY) {
-                        queries.add(parseContext.parseInnerQuery());
+                        Query query = parseContext.parseInnerQuery();
+                        if (query != null) {
+                            queries.add(query);
+                        }
                         token = parser.nextToken();
                     }
                 } else {
@@ -86,6 +95,14 @@ public class DisMaxQueryParser implements QueryParser {
             }
         }
 
+        if (!queriesFound) {
+            throw new QueryParsingException(parseContext.index(), "[dis_max] requires 'queries' field");
+        }
+
+        if (queries.isEmpty()) {
+            return null;
+        }
+
         DisjunctionMaxQuery query = new DisjunctionMaxQuery(queries, tieBreaker);
         query.setBoost(boost);
         return query;

src/main/java/org/elasticsearch/index/query/FQueryFilterParser.java

@@ -50,6 +50,7 @@ public class FQueryFilterParser implements FilterParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         boolean cache = false;
         CacheKeyFilter.Key cacheKey = null;
 
@@ -61,6 +62,7 @@ public class FQueryFilterParser implements FilterParser {
                 currentFieldName = parser.currentName();
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("query".equals(currentFieldName)) {
+                    queryFound = true;
                     query = parseContext.parseInnerQuery();
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[fquery] filter does not support [" + currentFieldName + "]");
@@ -77,6 +79,12 @@ public class FQueryFilterParser implements FilterParser {
                 }
             }
         }
+        if (!queryFound) {
+            throw new QueryParsingException(parseContext.index(), "[fquery] requires 'query' element");
+        }
+        if (query == null) {
+            return null;
+        }
         Filter filter = new QueryWrapperFilter(query);
         if (cache) {
             filter = parseContext.cacheFilter(filter, cacheKey);

src/main/java/org/elasticsearch/index/query/FilterParser.java

@@ -20,6 +20,7 @@
 package org.elasticsearch.index.query;
 
 import org.apache.lucene.search.Filter;
+import org.elasticsearch.common.Nullable;
 
 import java.io.IOException;
 
@@ -37,5 +38,6 @@ public interface FilterParser {
      * Parses the into a filter from the current parser location. Will be at "START_OBJECT" location,
      * and should end when the token is at the matching "END_OBJECT".
      */
+    @Nullable
     Filter parse(QueryParseContext parseContext) throws IOException, QueryParsingException;
 }

src/main/java/org/elasticsearch/index/query/FilteredQueryParser.java

@@ -51,7 +51,9 @@ public class FilteredQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         Filter filter = null;
+        boolean filterFound = false;
         float boost = 1.0f;
         boolean cache = false;
         CacheKeyFilter.Key cacheKey = null;
@@ -63,8 +65,10 @@ public class FilteredQueryParser implements QueryParser {
                 currentFieldName = parser.currentName();
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("query".equals(currentFieldName)) {
+                    queryFound = true;
                     query = parseContext.parseInnerQuery();
                 } else if ("filter".equals(currentFieldName)) {
+                    filterFound = true;
                     filter = parseContext.parseInnerFilter();
                 } else {
                     throw new QueryParsingException(parseContext.index(), "[filtered] query does not support [" + currentFieldName + "]");
@@ -81,12 +85,21 @@ public class FilteredQueryParser implements QueryParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[filtered] requires 'query' element");
         }
-        // we allow for null filter, so it makes compositions on the client side to be simpler
+        if (query == null) {
+            return null;
+        }
         if (filter == null) {
+            if (!filterFound) {
+                // we allow for null filter, so it makes compositions on the client side to be simpler
                 return query;
+            } else {
+                // the filter was provided, but returned null, meaning we should discard it, this means no
+                // matches for this query...
+                return Queries.NO_MATCH_QUERY;
+            }
         }
 
         // cache if required

src/main/java/org/elasticsearch/index/query/HasChildFilterParser.java

@@ -52,6 +52,7 @@ public class HasChildFilterParser implements FilterParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         String childType = null;
         String scope = null;
 
@@ -68,6 +69,7 @@ public class HasChildFilterParser implements FilterParser {
                     String[] origTypes = QueryParseContext.setTypesWithPrevious(childType == null ? null : new String[]{childType});
                     try {
                         query = parseContext.parseInnerQuery();
+                        queryFound = true;
                     } finally {
                         QueryParseContext.setTypes(origTypes);
                     }
@@ -86,9 +88,12 @@ public class HasChildFilterParser implements FilterParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[child] filter requires 'query' field");
         }
+        if (query == null) {
+            return null;
+        }
         if (childType == null) {
             throw new QueryParsingException(parseContext.index(), "[child] filter requires 'type' field");
         }

src/main/java/org/elasticsearch/index/query/HasChildQueryParser.java

@@ -52,6 +52,7 @@ public class HasChildQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         float boost = 1.0f;
         String childType = null;
         String scope = null;
@@ -68,6 +69,7 @@ public class HasChildQueryParser implements QueryParser {
                     String[] origTypes = QueryParseContext.setTypesWithPrevious(childType == null ? null : new String[]{childType});
                     try {
                         query = parseContext.parseInnerQuery();
+                        queryFound = true;
                     } finally {
                         QueryParseContext.setTypes(origTypes);
                     }
@@ -86,9 +88,12 @@ public class HasChildQueryParser implements QueryParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[has_child] requires 'query' field");
         }
+        if (query == null) {
+            return null;
+        }
         if (childType == null) {
             throw new QueryParsingException(parseContext.index(), "[has_child] requires 'type' field");
         }

src/main/java/org/elasticsearch/index/query/IndexQueryParserService.java

@@ -26,6 +26,7 @@ import org.elasticsearch.ElasticSearchException;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.io.BytesStream;
+import org.elasticsearch.common.lucene.search.Queries;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentParser;
@@ -232,12 +233,14 @@ public class IndexQueryParserService extends AbstractIndexComponent {
         }
     }
 
+    @Nullable
     public Filter parseInnerFilter(XContentParser parser) throws IOException {
         QueryParseContext context = cache.get();
         context.reset(parser);
         return context.parseInnerFilter();
     }
 
+    @Nullable
     public Query parseInnerQuery(XContentParser parser) throws IOException {
         QueryParseContext context = cache.get();
         context.reset(parser);
@@ -247,6 +250,9 @@ public class IndexQueryParserService extends AbstractIndexComponent {
     private ParsedQuery parse(QueryParseContext parseContext, XContentParser parser) throws IOException, QueryParsingException {
         parseContext.reset(parser);
         Query query = parseContext.parseInnerQuery();
+        if (query == null) {
+            query = Queries.NO_MATCH_QUERY;
+        }
         return new ParsedQuery(query, parseContext.copyNamedFilters());
     }
 

src/main/java/org/elasticsearch/index/query/IndicesFilterParser.java

@@ -56,6 +56,7 @@ public class IndicesFilterParser implements FilterParser {
         XContentParser parser = parseContext.parser();
 
         Filter filter = null;
+        boolean filterFound = false;
         Set<String> indices = Sets.newHashSet();
 
         String currentFieldName = null;
@@ -66,6 +67,7 @@ public class IndicesFilterParser implements FilterParser {
                 currentFieldName = parser.currentName();
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("filter".equals(currentFieldName)) {
+                    filterFound = true;
                     filter = parseContext.parseInnerFilter();
                 } else if ("no_match_filter".equals(currentFieldName)) {
                     noMatchFilter = parseContext.parseInnerFilter();
@@ -99,13 +101,17 @@ public class IndicesFilterParser implements FilterParser {
                 }
             }
         }
-        if (filter == null) {
+        if (!filterFound) {
             throw new QueryParsingException(parseContext.index(), "[indices] requires 'filter' element");
         }
         if (indices.isEmpty()) {
             throw new QueryParsingException(parseContext.index(), "[indices] requires 'indices' element");
         }
 
+        if (filter == null) {
+            return null;
+        }
+
         String[] concreteIndices = indices.toArray(new String[indices.size()]);
         if (clusterService != null) {
             MetaData metaData = clusterService.state().metaData();

src/main/java/org/elasticsearch/index/query/IndicesQueryParser.java

@@ -57,6 +57,7 @@ public class IndicesQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         Set<String> indices = Sets.newHashSet();
 
         String currentFieldName = null;
@@ -68,6 +69,7 @@ public class IndicesQueryParser implements QueryParser {
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("query".equals(currentFieldName)) {
                     query = parseContext.parseInnerQuery();
+                    queryFound = true;
                 } else if ("no_match_query".equals(currentFieldName)) {
                     noMatchQuery = parseContext.parseInnerQuery();
                 } else {
@@ -100,9 +102,12 @@ public class IndicesQueryParser implements QueryParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[indices] requires 'query' element");
         }
+        if (query == null) {
+            return null;
+        }
         if (indices.isEmpty()) {
             throw new QueryParsingException(parseContext.index(), "[indices] requires 'indices' element");
         }

src/main/java/org/elasticsearch/index/query/NestedFilterParser.java

@@ -50,7 +50,9 @@ public class NestedFilterParser implements FilterParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         Filter filter = null;
+        boolean filterFound = false;
         float boost = 1.0f;
         String scope = null;
         String path = null;
@@ -72,8 +74,10 @@ public class NestedFilterParser implements FilterParser {
                     currentFieldName = parser.currentName();
                 } else if (token == XContentParser.Token.START_OBJECT) {
                     if ("query".equals(currentFieldName)) {
+                        queryFound = true;
                         query = parseContext.parseInnerQuery();
                     } else if ("filter".equals(currentFieldName)) {
+                        filterFound = true;
                         filter = parseContext.parseInnerFilter();
                     } else {
                         throw new QueryParsingException(parseContext.index(), "[nested] filter does not support [" + currentFieldName + "]");
@@ -96,13 +100,17 @@ public class NestedFilterParser implements FilterParser {
                     }
                 }
             }
-            if (query == null && filter == null) {
+            if (!queryFound && !filterFound) {
                 throw new QueryParsingException(parseContext.index(), "[nested] requires either 'query' or 'filter' field");
             }
             if (path == null) {
                 throw new QueryParsingException(parseContext.index(), "[nested] requires 'path' field");
             }
 
+            if (query == null && filter == null) {
+                return null;
+            }
+
             if (filter != null) {
                 query = new DeletionAwareConstantScoreQuery(filter);
             }

src/main/java/org/elasticsearch/index/query/NestedQueryParser.java

@@ -50,7 +50,9 @@ public class NestedQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         Filter filter = null;
+        boolean filterFound = false;
         float boost = 1.0f;
         String scope = null;
         String path = null;
@@ -70,8 +72,10 @@ public class NestedQueryParser implements QueryParser {
                     currentFieldName = parser.currentName();
                 } else if (token == XContentParser.Token.START_OBJECT) {
                     if ("query".equals(currentFieldName)) {
+                        queryFound = true;
                         query = parseContext.parseInnerQuery();
                     } else if ("filter".equals(currentFieldName)) {
+                        filterFound = true;
                         filter = parseContext.parseInnerFilter();
                     } else {
                         throw new QueryParsingException(parseContext.index(), "[nested] query does not support [" + currentFieldName + "]");
@@ -101,13 +105,17 @@ public class NestedQueryParser implements QueryParser {
                     }
                 }
             }
-            if (query == null && filter == null) {
+            if (!queryFound && !filterFound) {
                 throw new QueryParsingException(parseContext.index(), "[nested] requires either 'query' or 'filter' field");
             }
             if (path == null) {
                 throw new QueryParsingException(parseContext.index(), "[nested] requires 'path' field");
             }
 
+            if (query == null && filter == null) {
+                return null;
+            }
+
             if (filter != null) {
                 query = new DeletionAwareConstantScoreQuery(filter);
             }

src/main/java/org/elasticsearch/index/query/NotFilterParser.java

@@ -48,6 +48,7 @@ public class NotFilterParser implements FilterParser {
         XContentParser parser = parseContext.parser();
 
         Filter filter = null;
+        boolean filterFound = false;
         boolean cache = false;
         CacheKeyFilter.Key cacheKey = null;
 
@@ -60,7 +61,9 @@ public class NotFilterParser implements FilterParser {
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("filter".equals(currentFieldName)) {
                     filter = parseContext.parseInnerFilter();
+                    filterFound = true;
                 } else {
+                    filterFound = true;
                     // its the filter, and the name is the field
                     filter = parseContext.parseInnerFilter(currentFieldName);
                 }
@@ -77,10 +80,14 @@ public class NotFilterParser implements FilterParser {
             }
         }
 
-        if (filter == null) {
+        if (!filterFound) {
             throw new QueryParsingException(parseContext.index(), "filter is required when using `not` filter");
         }
 
+        if (filter == null) {
+            return null;
+        }
+
         Filter notFilter = new NotFilter(filter);
         if (cache) {
             notFilter = parseContext.cacheFilter(notFilter, cacheKey);

src/main/java/org/elasticsearch/index/query/OrFilterParser.java

@@ -51,6 +51,7 @@ public class OrFilterParser implements FilterParser {
         XContentParser parser = parseContext.parser();
 
         ArrayList<Filter> filters = newArrayList();
+        boolean filtersFound = false;
 
         boolean cache = false;
         CacheKeyFilter.Key cacheKey = null;
@@ -60,7 +61,11 @@ public class OrFilterParser implements FilterParser {
         XContentParser.Token token = parser.currentToken();
         if (token == XContentParser.Token.START_ARRAY) {
             while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                filters.add(parseContext.parseInnerFilter());
+                filtersFound = true;
+                Filter filter = parseContext.parseInnerFilter();
+                if (filter != null) {
+                    filters.add(filter);
+                }
             }
         } else {
             while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
@@ -68,12 +73,20 @@ public class OrFilterParser implements FilterParser {
                     currentFieldName = parser.currentName();
                 } else if (token == XContentParser.Token.START_ARRAY) {
                     if ("filters".equals(currentFieldName)) {
+                        filtersFound = true;
                         while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                            filters.add(parseContext.parseInnerFilter());
+                            Filter filter = parseContext.parseInnerFilter();
+                            if (filter != null) {
+                                filters.add(filter);
+                            }
                         }
                     } else {
                         while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
-                            filters.add(parseContext.parseInnerFilter());
+                            filtersFound = true;
+                            Filter filter = parseContext.parseInnerFilter();
+                            if (filter != null) {
+                                filters.add(filter);
+                            }
                         }
                     }
                 } else if (token.isValue()) {
@@ -90,10 +103,14 @@ public class OrFilterParser implements FilterParser {
             }
         }
 
-        if (filters.isEmpty()) {
+        if (!filtersFound) {
             throw new QueryParsingException(parseContext.index(), "[or] filter requires 'filters' to be set on it'");
         }
 
+        if (filters.isEmpty()) {
+            return null;
+        }
+
         // no need to cache this one
         Filter filter = new OrFilter(filters);
         if (cache) {

src/main/java/org/elasticsearch/index/query/QueryFilterParser.java

@@ -45,6 +45,9 @@ public class QueryFilterParser implements FilterParser {
     @Override
     public Filter parse(QueryParseContext parseContext) throws IOException, QueryParsingException {
         Query query = parseContext.parseInnerQuery();
+        if (query == null) {
+            return null;
+        }
         return new QueryWrapperFilter(query);
     }
 }

src/main/java/org/elasticsearch/index/query/QueryParseContext.java

@@ -160,6 +160,7 @@ public class QueryParseContext {
         return ImmutableMap.copyOf(namedFilters);
     }
 
+    @Nullable
     public Query parseInnerQuery() throws IOException, QueryParsingException {
         // move to START object
         XContentParser.Token token;
@@ -192,6 +193,7 @@ public class QueryParseContext {
         return result;
     }
 
+    @Nullable
     public Filter parseInnerFilter() throws IOException, QueryParsingException {
         // move to START object
         XContentParser.Token token;

src/main/java/org/elasticsearch/index/query/QueryParser.java

@@ -20,6 +20,7 @@
 package org.elasticsearch.index.query;
 
 import org.apache.lucene.search.Query;
+import org.elasticsearch.common.Nullable;
 
 import java.io.IOException;
 
@@ -36,6 +37,9 @@ public interface QueryParser {
     /**
      * Parses the into a query from the current parser location. Will be at "START_OBJECT" location,
      * and should end when the token is at the matching "END_OBJECT".
+     * <p/>
+     * Returns <tt>null</tt> if this query should be ignored in the context of the DSL.
      */
+    @Nullable
     Query parse(QueryParseContext parseContext) throws IOException, QueryParsingException;
 }

src/main/java/org/elasticsearch/index/query/TopChildrenQueryParser.java

@@ -51,6 +51,7 @@ public class TopChildrenQueryParser implements QueryParser {
         XContentParser parser = parseContext.parser();
 
         Query query = null;
+        boolean queryFound = false;
         float boost = 1.0f;
         String childType = null;
         String scope = null;
@@ -65,6 +66,7 @@ public class TopChildrenQueryParser implements QueryParser {
                 currentFieldName = parser.currentName();
             } else if (token == XContentParser.Token.START_OBJECT) {
                 if ("query".equals(currentFieldName)) {
+                    queryFound = true;
                     // TODO we need to set the type, but, `query` can come before `type`... (see HasChildFilterParser)
                     // since we switch types, make sure we change the context
                     String[] origTypes = QueryParseContext.setTypesWithPrevious(childType == null ? null : new String[]{childType});
@@ -94,13 +96,17 @@ public class TopChildrenQueryParser implements QueryParser {
                 }
             }
         }
-        if (query == null) {
+        if (!queryFound) {
             throw new QueryParsingException(parseContext.index(), "[child] requires 'query' field");
         }
         if (childType == null) {
             throw new QueryParsingException(parseContext.index(), "[child] requires 'type' field");
         }
 
+        if (query == null) {
+            return null;
+        }
+
         DocumentMapper childDocMapper = parseContext.mapperService().documentMapper(childType);
         if (childDocMapper == null) {
             throw new QueryParsingException(parseContext.index(), "No mapping for for type [" + childType + "]");