CBL-6285: Explain for predictive query no longer names an index

Update the default table name from main source in the query expression.

When we create the query object from the database, with, for example, SQLiteDataFile::compileQuery, the defaultTableName of QueryTranslator is initialized with the table name of the default collection. This table is assumed to be the main data source of the query expression. Therefore, we need to update it as we parse the first item in the FROM clause, before PredictionNode is created.

Author: jianminzhao

Diff for: LiteCore/Query/Translator/Node.hh

@@ -76,6 +76,7 @@ namespace litecore::qt {
 #ifdef COUCHBASE_ENTERPRISE
         std::function<bool(string_view id)> hasPredictiveIndex;
 #endif
+        std::function<void(SourceNode*)> updateDefaultTableName;
     };
 
     /** State used during parsing, passed down through the recursive descent. */

Diff for: LiteCore/Query/Translator/QueryTranslator.cc

@@ -44,6 +44,9 @@ namespace litecore {
             return _delegate.tableExists(indexTable);
         };
 #endif
+        root.updateDefaultTableName = [&](SourceNode* source) -> void {
+            _defaultTableName = tableNameForCollectionSource(source);
+        };
         return root;
     }
 
@@ -112,6 +115,21 @@ namespace litecore {
         }
     }
 
+    string QueryTranslator::tableNameForCollectionSource(SourceNode* source) const {
+        string name(source->collection());
+        if ( name.empty() ) name = _defaultCollectionName;
+        if ( !source->scope().empty() ) name = string(source->scope()) + "." + name;
+
+        DeletionStatus delStatus = source->usesDeletedDocs() ? kLiveAndDeletedDocs : kLiveDocs;
+        //FIXME: Support kDeletedDocs
+
+        string tableName = _delegate.collectionTableName(name, delStatus);
+        if ( name != _defaultCollectionName && !_delegate.tableExists(tableName) )
+            fail("no such collection \"%s\"", name.c_str());
+
+        return tableName;
+    }
+
     string QueryTranslator::tableNameForSource(SourceNode* source, ParseContext& ctx) {
         string tableName(source->tableName());
         if ( !tableName.empty() ) return tableName;
@@ -129,17 +147,7 @@ namespace litecore {
             _hashedTables.emplace(tableName, plainTableName);
             if ( _delegate.tableExists(tableName) ) source->setTableName(ctx.newString(tableName));
         } else {
-            string name(source->collection());
-            if ( name.empty() ) name = _defaultCollectionName;
-            if ( !source->scope().empty() ) name = string(source->scope()) + "." + name;
-
-            DeletionStatus delStatus = source->usesDeletedDocs() ? kLiveAndDeletedDocs : kLiveDocs;
-            //FIXME: Support kDeletedDocs
-
-            tableName = _delegate.collectionTableName(name, delStatus);
-            if ( name != _defaultCollectionName && !_delegate.tableExists(tableName) )
-                fail("no such collection \"%s\"", name.c_str());
-
+            tableName = tableNameForCollectionSource(source);
             if ( auto index = dynamic_cast<IndexSourceNode*>(source) ) {
                 switch ( index->indexType() ) {
                     case IndexType::FTS:
@@ -164,6 +172,7 @@ namespace litecore {
 #endif
                 }
             } else if ( source->isCollection() ) {
+                DeletionStatus delStatus = source->usesDeletedDocs() ? kLiveAndDeletedDocs : kLiveDocs;
                 if ( delStatus != kLiveAndDeletedDocs )  // that mode uses a fake union table
                     _kvTables.insert(tableName);
             }

Diff for: LiteCore/Query/Translator/QueryTranslator.hh

@@ -125,6 +125,7 @@ namespace litecore {
       private:
         QueryTranslator(const QueryTranslator& qp)         = delete;
         QueryTranslator& operator=(const QueryTranslator&) = delete;
+        string           tableNameForCollectionSource(qt::SourceNode*) const;
         string           tableNameForSource(qt::SourceNode*, qt::ParseContext&);
         void             assignTableNameToSource(qt::SourceNode*, qt::ParseContext&);
         string           writeSQL(function_ref<void(qt::SQLWriter&)>);
@@ -133,7 +134,7 @@ namespace litecore {
         qt::RootContext  makeRootContext() const;
 
         const Delegate&                    _delegate;               // delegate object (SQLiteKeyStore)
-        string                             _defaultTableName;       // Name of the default table to use
+        mutable string                     _defaultTableName;       // Name of the default table to use
         string                             _defaultCollectionName;  // Name of the default collection to use
         string                             _sql;                    // The generated SQL
         std::set<string>                   _parameters;             // Plug-in "$" parameters found in parsing

Diff for: LiteCore/Query/Translator/SelectNodes.cc

@@ -481,6 +481,7 @@ namespace litecore::qt {
                 isFrom = true;
                 require(_sources.empty(), "multiple non-join FROM items");
                 ctx.from = source;
+                ctx.delegate.updateDefaultTableName(source);
             }
             ctx.sources.emplace_back(source);
         }

Diff for: LiteCore/tests/PredictiveQueryTest.cc

@@ -11,6 +11,7 @@
 //
 
 #include "QueryTest.hh"
+#include "c4QueryTypes.h"
 #include "PredictiveModel.hh"
 #include <cmath>
 
@@ -206,10 +207,11 @@ N_WAY_TEST_CASE_METHOD(QueryTest, "Predictive Query compound indexed", "[Query][
         // Query numbers in descending order of square-ness:
         std::stringstream sstr;
         sstr << "{'WHAT': [['.num'], " << square << "],"
+             << " 'FROM': [{'COLLECTION': '" + collectionName + "'}],"
              << " 'WHERE': ['AND', ['>=', " << square + ", 1], ['>=', " << even << ", 1]],"
              << " 'ORDER_BY': [['DESC', ['.num']]] }";
 
-        Retained<Query> query{store->compileQuery(json5(sstr.str()))};
+        Retained<Query> query{db->compileQuery(json5(sstr.str()))};
         string          explanation = query->explain();
         Log("Explanation: %s", explanation.c_str());