Bail out earlier when walking parse tree

No point walking the parse tree, if no information will be
collected.

query_classifier/qc_sqlite/qc_sqlite.cc

@@ -484,19 +484,27 @@ public:
     // PUBLIC for now at least.
 
     /**
-     * Returns whether a field is sequence related.
+     * Returns whether sequence related functions should be checked for.
      *
-     * @param zDatabase  The database/schema or NULL.
+     * Only if we are in Oracle mode or parsing as 10.3 we need to check.
-     * @param zTable     The table or NULL.
-     * @param zColumn    The column.
      *
-     * @return True, if the field is sequence related, false otherwise.
+     * @return True, if they need to be checked for, false otherwise.
      */
-    bool is_sequence_related_field(const char* zDatabase,
+    bool must_check_sequence_related_functions() const
-                                   const char* zTable,
-                                   const char* zColumn) const
     {
-        return is_sequence_related_function(zColumn);
+        return (m_sql_mode == QC_SQL_MODE_ORACLE) || (this_unit.parse_as == QC_PARSE_AS_103);
+    }
+
+    /**
+     * Returns whether fields should be collected.
+     *
+     * @return True, if should be, false otherwise.
+     */
+    bool must_collect_fields() const
+    {
+        // We must collect if fields should be collected and they have not
+        // been collected yet.
+        return (m_collect & QC_COLLECT_FIELDS) && !(m_collected & QC_COLLECT_FIELDS);
     }
 
     /**
@@ -534,6 +542,22 @@ public:
         return rv;
     }
 
+    /**
+     * Returns whether a field is sequence related.
+     *
+     * @param zDatabase  The database/schema or NULL.
+     * @param zTable     The table or NULL.
+     * @param zColumn    The column.
+     *
+     * @return True, if the field is sequence related, false otherwise.
+     */
+    bool is_sequence_related_field(const char* zDatabase,
+                                   const char* zTable,
+                                   const char* zColumn) const
+    {
+        return is_sequence_related_function(zColumn);
+    }
+
     static void honour_aliases(const QcAliases* pAliases,
                                const char** pzDatabase,
                                const char** pzTable)
@@ -614,13 +638,14 @@ public:
 
         // NOTE: This must be first, so that the type mask is properly updated
         // NOTE: in case zColumn is "currval" etc.
-        if (is_sequence_related_field(zDatabase, zTable, zColumn))
+        if (must_check_sequence_related_functions() &&
+            is_sequence_related_field(zDatabase, zTable, zColumn))
         {
             m_type_mask |= QUERY_TYPE_WRITE;
             return;
         }
 
-        if (!(m_collect & QC_COLLECT_FIELDS) || (m_collected & QC_COLLECT_FIELDS))
+        if (!must_collect_fields())
         {
             // If field information should not be collected, or if field information
             // has already been collected, we just return.
@@ -669,6 +694,8 @@ public:
         bool should_collect_database = zDatabase &&
             (should_collect_alias || should_collect(QC_COLLECT_DATABASES));
 
+        if (should_collect_table || should_collect_database)
+        {
             const char* zCollected_database = NULL;
             const char* zCollected_table = NULL;
 
@@ -707,6 +734,7 @@ public:
                 pAliases->insert(QcAliases::value_type(zAlias, value));
             }
         }
+    }
 
     static int32_t type_check_dynamic_string(const Expr* pExpr)
     {
@@ -1145,11 +1173,14 @@ public:
         const char* zTable;
         const char* zColumn;
 
+        if (must_check_sequence_related_functions() || must_collect_fields())
+        {
             if (get_field_name(pExpr, &zDatabase, &zTable, &zColumn))
             {
                 update_field_info(pAliases, zDatabase, zTable, zColumn, pExclude);
             }
         }
+    }
 
     void update_field_infos_from_exprlist(QcAliases* pAliases,
                                           const ExprList* pEList,
@@ -1166,6 +1197,8 @@ public:
     void update_field_infos_from_idlist(QcAliases* pAliases,
                                         const IdList* pIds,
                                         const ExprList* pExclude)
+    {
+        if (must_check_sequence_related_functions() || must_collect_fields())
         {
             for (int i = 0; i < pIds->nId; ++i)
             {
@@ -1174,6 +1207,7 @@ public:
                 update_field_info(pAliases, NULL, NULL, pItem->zName, pExclude);
             }
         }
+    }
 
     enum compound_approach_t
     {