MDEV-23886 Reusing CTE inside a function fails with table doesn't exist

In the code existed just before this patch binding of a table reference to
the specification of the corresponding CTE happens in the function
open_and_process_table(). If the table reference is not the first in the
query the specification is cloned in the same way as the specification of
a view is cloned for any reference of the view. This works fine for
standalone queries, but does not work for stored procedures / functions
for the following reason.
When the first call of a stored procedure/ function SP is processed the
body of SP is parsed. When a query of SP is parsed the info on each
encountered table reference is put into a TABLE_LIST object linked into
a global chain associated with the query. When parsing of the query is
finished the basic info on the table references from this chain except
table references to derived tables and information schema tables is put
in one hash table associated with SP. When parsing of the body of SP is
finished this hash table is used to construct TABLE_LIST objects for all
table references mentioned in SP and link them into the list of such
objects passed to a pre-locking process that calls open_and_process_table()
for each table from the list.
When a TABLE_LIST for a view is encountered the view is opened and its
specification is parsed. For any table reference occurred in
the specification a new TABLE_LIST object is created to be included into
the list for pre-locking. After all objects in the pre-locking have been
looked through the tables mentioned in the list are locked. Note that the
objects referenced CTEs are just skipped here as it is impossible to
resolve these references without any info on the context where they occur.
Now the statements from the body of SP are executed one by one that.
At the very beginning of the execution of a query the tables used in the
query are opened and open_and_process_table() now is called for each table
reference mentioned in the list of TABLE_LIST objects associated with the
query that was built when the query was parsed.
For each table reference first the reference is checked against CTEs
definitions in whose scope it occurred. If such definition is found the
reference is considered resolved and if this is not the first reference
to the found CTE the the specification of the CTE is re-parsed and the
result of the parsing is added to the parsing tree of the query as a
sub-tree. If this sub-tree contains table references to other tables they
are added to the list of TABLE_LIST objects associated with the query in
order the referenced tables to be opened. When the procedure that opens
the tables comes to the TABLE_LIST object created for a non-first
reference to a CTE it discovers that the referenced table instance is not
locked and reports an error.
Thus processing non-first table references to a CTE similar to how
references to view are processed does not work for queries used in stored
procedures / functions. And the main problem is that the current
pre-locking mechanism employed for stored procedures / functions does not
allow to save the context in which a CTE reference occur. It's not trivial
to save the info about the context where a CTE reference occurs while the
resolution of the table reference cannot be done without this context and
consequentially the specification for the table reference cannot be
determined.

This patch solves the above problem by moving resolution of all CTE
references at the parsing stage. More exactly references to CTEs occurred in
a query are resolved right after parsing of the query has finished. After
resolution any CTE reference it is marked as a reference to to derived
table. So it is excluded from the hash table created for pre-locking used
base tables and view when the first call of a stored procedure / function
is processed.
This solution required recursive calls of the parser. The function
THD::sql_parser() has been added specifically for recursive invocations of
the parser.

1 files changed, 289 insertions, 131 deletions

diff --git a/sql/sql_cte.cc b/sql/sql_cte.cc
index f3861ebd3e9..dfcb4e18772 100644
--- a/sql/sql_cte.cc
+++ b/sql/sql_cte.cc
@@ -83,7 +83,7 @@ void  st_select_lex_unit::set_with_clause(With_clause *with_cl)
     true    on failure
 */
 
-bool check_dependencies_in_with_clauses(With_clause *with_clauses_list)
+bool LEX::check_dependencies_in_with_clauses()
 {
   for (With_clause *with_clause= with_clauses_list;
        with_clause;
@@ -101,6 +101,201 @@ bool check_dependencies_in_with_clauses(With_clause *with_clauses_list)
 
 /**
   @brief
+    Resolve references to CTE in specification of hanging CTE
+
+  @details
+    A CTE to which there are no references in the query is called hanging CTE.
+    Although such CTE is not used for execution its specification must be
+    subject to context analysis. All errors concerning references to
+    non-existing tables or fields occurred in the specification must be
+    reported as well as all other errors caught at the prepare stage.
+    The specification of a hanging CTE might contain references to other
+    CTE outside of the specification and within it if the specification
+    contains a with clause. This function resolves all such references for
+    all hanging CTEs encountered in the processed query.
+
+  @retval
+    false   on success
+    true    on failure
+*/
+
+bool
+LEX::resolve_references_to_cte_in_hanging_cte()
+{
+  for (With_clause *with_clause= with_clauses_list;
+       with_clause; with_clause= with_clause->next_with_clause)
+  {
+    for (With_element *with_elem= with_clause->with_list.first;
+         with_elem; with_elem= with_elem->next)
+    {
+      if (!with_elem->is_referenced())
+      {
+        TABLE_LIST *first_tbl=
+                     with_elem->spec->first_select()->table_list.first;
+        TABLE_LIST **with_elem_end_pos= with_elem->head->tables_pos.end_pos;
+        if (first_tbl && resolve_references_to_cte(first_tbl, with_elem_end_pos))
+          return true;
+      }
+    }
+  }
+  return false;
+}
+
+
+/**
+  @brief
+    Resolve table references to CTE from a sub-chain of table references
+
+  @param tables      Points to the beginning of the sub-chain
+  @param tables_last Points to the address with the sub-chain barrier
+
+  @details
+    The method resolves tables references to CTE from the chain of
+    table references specified by the parameters 'tables' and 'tables_last'.
+    It resolves the references against the CTE definition occurred in a query
+    or the specification of a CTE whose parsing tree is represented by
+    this LEX structure. The method is always called right after the process
+    of parsing the query or of the specification of a CTE has been finished,
+    thus the chain of table references used in the parsed fragment has been
+    already built. It is assumed that parameters of the method specify a
+    a sub-chain of this chain.
+    If a table reference can be potentially a table reference to a CTE and it
+    has not been resolved yet then the method tries to find the definition
+    of the CTE against which the reference can be resolved. If it succeeds
+    it sets the field TABLE_LIST::with to point to the found definition.
+    It also sets the field TABLE_LIST::derived to point to the specification
+    of the found CTE and sets TABLE::db.str to empty_c_string. This will
+    allow to handle this table reference like a reference to a derived handle.
+    If another table reference has been already resolved against this CTE
+    and this CTE is not recursive then a clone of the CTE specification is
+    constructed using the function With_element::clone_parsed_spec() and
+    TABLE_LIST::derived is set to point to this clone rather than to the
+    original specification.
+    If the method does not find a matched CTE definition in the parsed fragment
+    then in the case when the flag this->only_cte_resolution is set to true
+    it just moves to the resolution of the next table reference from the
+    specified sub-chain while in the case when this->only_cte_resolution is set
+    to false the method additionally sets an mdl request for this table
+    reference.
+
+  @notes
+    The flag this->only_cte_resolution is set to true in the cases when
+    the failure to resolve a table reference as a CTE reference within
+    the fragment associated with this LEX structure does not imply that
+    this table reference cannot be resolved as such at all.
+
+  @retval false  On success: no errors reported, no memory allocations failed
+  @retval true   Otherwise
+*/
+
+bool LEX::resolve_references_to_cte(TABLE_LIST *tables,
+                                    TABLE_LIST **tables_last)
+{
+  With_element *with_elem= 0;
+
+  for (TABLE_LIST *tbl= tables; tbl != *tables_last; tbl= tbl->next_global)
+  {
+    if (tbl->derived)
+      continue;
+    if (!tbl->db.str && !tbl->with)
+      tbl->with= tbl->select_lex->find_table_def_in_with_clauses(tbl);
+    if (!tbl->with)    // no CTE matches table reference tbl
+    {
+      if (only_cte_resolution)
+        continue;
+      if (!tbl->db.str)   // no database specified in table reference tbl
+      {
+        if (!thd->db.str) // no default database is set
+        {
+          my_message(ER_NO_DB_ERROR, ER(ER_NO_DB_ERROR), MYF(0));
+          return true;
+        }
+        if (copy_db_to(&tbl->db))
+          return true;
+        if (!(tbl->table_options & TL_OPTION_ALIAS))
+          tbl->mdl_request.init(MDL_key::TABLE, tbl->db.str,
+                                tbl->table_name.str,
+                                tbl->mdl_type, MDL_TRANSACTION);
+        tbl->mdl_request.set_type((tbl->lock_type >= TL_WRITE_ALLOW_WRITE) ?
+                                   MDL_SHARED_WRITE : MDL_SHARED_READ);
+      }
+      continue;
+    }
+    with_elem= tbl->with;
+    if (tbl->is_recursive_with_table() &&
+        !tbl->is_with_table_recursive_reference())
+    {
+      tbl->with->rec_outer_references++;
+      while ((with_elem= with_elem->get_next_mutually_recursive()) !=
+             tbl->with)
+	with_elem->rec_outer_references++;
+    }
+    if (!with_elem->is_used_in_query || with_elem->is_recursive)
+    {
+      tbl->derived= with_elem->spec;
+      if (tbl->derived != tbl->select_lex->master_unit() &&
+          !with_elem->is_recursive &&
+          !tbl->is_with_table_recursive_reference())
+      {
+        tbl->derived->move_as_slave(tbl->select_lex);
+      }
+      with_elem->is_used_in_query= true;
+    }
+    else
+    {
+      if (!(tbl->derived= tbl->with->clone_parsed_spec(thd->lex, tbl)))
+        return true;
+    }
+    tbl->db.str= empty_c_string;
+    tbl->db.length= 0;
+    tbl->schema_table= 0;
+    if (tbl->derived)
+    {
+      tbl->derived->first_select()->set_linkage(DERIVED_TABLE_TYPE);
+      tbl->select_lex->add_statistics(tbl->derived);
+    }
+    if (tbl->with->is_recursive && tbl->is_with_table_recursive_reference())
+      continue;
+    with_elem->inc_references();
+  }
+  return false;
+}
+
+
+/**
+  @brief
+    Find out dependencies between CTEs, resolve references to them
+
+  @details
+    The function can be called in two modes. With this->with_cte_resolution
+    set to false the function only finds out all dependencies between CTEs
+    used in a query expression with a WITH clause whose parsing has been
+    just finished. Based on these dependencies recursive CTEs are detected.
+    If this->with_cte_resolution is set to true the function additionally
+    resolves all references to CTE occurred in this query expression.
+
+  @retval
+    true   on failure
+    false  on success
+*/
+
+bool
+LEX::check_cte_dependencies_and_resolve_references()
+{
+  if (check_dependencies_in_with_clauses())
+    return true;
+  if (!with_cte_resolution)
+    return false;
+  if (resolve_references_to_cte(query_tables, query_tables_last))
+    return true;
+  if (resolve_references_to_cte_in_hanging_cte())
+    return true;
+  return false;
+}
+
+
+/**
+  @brief
     Check dependencies between tables defined in this with clause
 
  @details
@@ -137,10 +332,11 @@ bool With_clause::check_dependencies()
          elem != with_elem;
          elem= elem->next)
     {
-      if (lex_string_cmp(system_charset_info, with_elem->query_name,
-                         elem->query_name) == 0)
+      if (lex_string_cmp(system_charset_info, with_elem->get_name(),
+                         elem->get_name()) == 0)
       {
-	my_error(ER_DUP_QUERY_NAME, MYF(0), with_elem->query_name->str);
+        my_error(ER_DUP_QUERY_NAME, MYF(0),
+                 with_elem->get_name_str());
 	return true;
       }
     }
@@ -247,13 +443,12 @@ With_element *With_clause::find_table_def(TABLE_LIST *table,
        with_elem != barrier;
        with_elem= with_elem->next)
   {
-    if (my_strcasecmp(system_charset_info, with_elem->query_name->str,
-		      table->table_name.str) == 0 &&
+    if (my_strcasecmp(system_charset_info, with_elem->get_name_str(),
+                      table->table_name.str) == 0 &&
         !table->is_fqtn)
     {
       table->set_derived();
-      table->db.str= empty_c_string;
-      table->db.length= 0;
+      with_elem->referenced= true;
       return with_elem;
     }
   }
@@ -610,7 +805,7 @@ bool With_clause::check_anchors()
       if (elem == with_elem)
       {
         my_error(ER_RECURSIVE_WITHOUT_ANCHORS, MYF(0),
-        with_elem->query_name->str);
+        with_elem->get_name_str());
         return true;
       }
     }
@@ -643,7 +838,7 @@ bool With_clause::check_anchors()
         if (elem->work_dep_map & elem->get_elem_map())
 	{
           my_error(ER_UNACCEPTABLE_MUTUAL_RECURSION, MYF(0),
-          with_elem->query_name->str);
+          with_elem->get_name_str());
           return true;
 	}
       }
@@ -797,7 +992,8 @@ bool With_element::set_unparsed_spec(THD *thd,
   @brief
    Create a clone of the specification for the given with table
     
-  @param thd        The context of the statement containing this with element
+  @param old_lex    The LEX structure created for the query or CTE specification
+                    where this With_element is defined
   @param with_table The reference to the table defined in this element for which
                      the clone is created.
 
@@ -807,12 +1003,13 @@ bool With_element::set_unparsed_spec(THD *thd,
     this element.
     The clone is created when the string with the specification saved in
     unparsed_spec is fed into the parser as an input string. The parsing
-    this string a unit object representing the specification is build.
+    this string a unit object representing the specification is built.
     A chain of all table references occurred in the specification is also
     formed.
     The method includes the new unit and its sub-unit into hierarchy of
     the units of the main query. I also insert the constructed chain of the 
     table references into the chain of all table references of the main query.
+    The method resolves all references to CTE in the clone.
 
   @note
     Clones is created only for not first references to tables defined in
@@ -828,114 +1025,128 @@ bool With_element::set_unparsed_spec(THD *thd,
      NULL - otherwise
 */
 
-st_select_lex_unit *With_element::clone_parsed_spec(THD *thd,
+st_select_lex_unit *With_element::clone_parsed_spec(LEX *old_lex,
                                                     TABLE_LIST *with_table)
 {
+  THD *thd= old_lex->thd;
   LEX *lex;
-  st_select_lex_unit *res= NULL; 
-  Query_arena backup;
-  Query_arena *arena= thd->activate_stmt_arena_if_needed(&backup);
+  st_select_lex_unit *res= NULL;
 
   if (!(lex= (LEX*) new(thd->mem_root) st_lex_local))
-  {
-    if (arena)
-      thd->restore_active_arena(arena, &backup);
     return res;
-  }
-  LEX *old_lex= thd->lex;
   thd->lex= lex;
 
   bool parse_status= false;
-  Parser_state parser_state;
-  TABLE_LIST *spec_tables;
-  TABLE_LIST *spec_tables_tail;
   st_select_lex *with_select;
 
   char save_end= unparsed_spec.str[unparsed_spec.length];
   ((char*) &unparsed_spec.str[unparsed_spec.length])[0]= '\0';
-  if (parser_state.init(thd, (char*) unparsed_spec.str, (unsigned int)unparsed_spec.length))
-    goto err;
-  parser_state.m_lip.stmt_prepare_mode= stmt_prepare_mode;
-  parser_state.m_lip.multi_statements= false;
-  parser_state.m_lip.m_digest= NULL;
 
   lex_start(thd);
   lex->clone_spec_offset= unparsed_spec_offset;
-  lex->param_list= old_lex->param_list;
-  lex->sphead= old_lex->sphead;
-  lex->spname= old_lex->spname;
-  lex->spcont= old_lex->spcont;
-  lex->sp_chistics= old_lex->sp_chistics;
-
-  lex->stmt_lex= old_lex;
-  parse_status= parse_sql(thd, &parser_state, 0);
+  lex->with_cte_resolution= true;
+
+  /*
+    The specification of a CTE is to be parsed as a regular query.
+    At the very end of the parsing query the function
+    check_cte_dependencies_and_resolve_references() will be called.
+    It will check the dependencies between CTEs that are defined
+    within the query and will resolve CTE references in this query.
+    If a table reference is not resolved as a CTE reference within
+    this query it still can be resolved as a reference to a CTE defined
+    in the same clause as the CTE whose specification is to be parsed
+    or defined in an embedding CTE definition.
+
+    Example:
+      with
+      cte1 as ( ... ),
+      cte2 as ([WITH ...] select ... from cte1 ...)
+      select ... from cte2 as r, ..., cte2 as s ...
+
+    Here the specification of cte2 has be cloned for table reference
+    with alias s1. The specification contains a reference to cte1
+    that is defined outside this specification. If the reference to
+    cte1 cannot be resolved within the specification of cte2 it's
+    not necessarily has to be a reference to a non-CTE table. That's
+    why the flag lex->only_cte_resolution has to be set to true
+    before parsing of the specification of cte2 invoked by this
+    function starts. Otherwise an mdl_lock would be requested for s
+    and this would not be correct.
+  */
+
+  lex->only_cte_resolution= true;
+
+  lex->stmt_lex= old_lex->stmt_lex ? old_lex->stmt_lex : old_lex;
+
+  parse_status= thd->sql_parser(old_lex, lex,
+                                (char*) unparsed_spec.str,
+                                (unsigned int)unparsed_spec.length,
+                                stmt_prepare_mode);
+
   ((char*) &unparsed_spec.str[unparsed_spec.length])[0]= save_end;
-  with_select= lex->first_select_lex();
+  with_select= lex->unit.first_select();
 
   if (parse_status)
     goto err;
 
-  if (check_dependencies_in_with_clauses(lex->with_clauses_list))
-    goto err;
-
-  spec_tables= lex->query_tables;
-  spec_tables_tail= 0;
-  for (TABLE_LIST *tbl= spec_tables;
-       tbl;
-       tbl= tbl->next_global)
-  {
-    if (!tbl->derived && !tbl->schema_table &&
-        thd->open_temporary_table(tbl))
-      goto err;
-    spec_tables_tail= tbl;
-  }
-  if (spec_tables)
+  /*
+    The global chain of TABLE_LIST objects created for the specification that
+    just has been parsed is added to such chain that contains the reference
+    to the CTE whose specification is parsed right after the TABLE_LIST object
+    created for the reference.
+  */
+  if (lex->query_tables)
   {
-    if (with_table->next_global)
+    head->tables_pos.set_start_pos(&with_table->next_global);
+    head->tables_pos.set_end_pos(lex->query_tables_last);
+    TABLE_LIST *next_tbl= with_table->next_global;
+    if (next_tbl)
     {
-      spec_tables_tail->next_global= with_table->next_global;
-      with_table->next_global->prev_global= &spec_tables_tail->next_global;
+      *(lex->query_tables->prev_global= next_tbl->prev_global)=
+        lex->query_tables;
+      *(next_tbl->prev_global= lex->query_tables_last)= next_tbl;
     }
     else
     {
-      old_lex->query_tables_last= &spec_tables_tail->next_global;
+      *(lex->query_tables->prev_global= old_lex->query_tables_last)=
+        lex->query_tables;
+      old_lex->query_tables_last= lex->query_tables_last;
     }
-    spec_tables->prev_global= &with_table->next_global;
-    with_table->next_global= spec_tables;
   }
   res= &lex->unit;
   res->with_element= this;
   
+  /*
+    The unit of the specification that just has been parsed is included
+    as a slave of the select that contained in its from list the table
+    reference for which the unit has been created.
+  */
   lex->unit.include_down(with_table->select_lex);
-  lex->unit.set_slave(with_select); 
+  lex->unit.set_slave(with_select);
+  lex->unit.cloned_from= spec;
   old_lex->all_selects_list=
     (st_select_lex*) (lex->all_selects_list->
 		      insert_chain_before(
 			(st_select_lex_node **) &(old_lex->all_selects_list),
                         with_select));
-  if (check_dependencies_in_with_clauses(lex->with_clauses_list))
-    res= NULL;
+
   /*
-    Resolve references to CTE from the spec_tables list that has not
-    been resolved yet.
+    Now all references to the CTE defined outside of the cloned specification
+    has to be resolved. Additionally if old_lex->only_cte_resolution == false
+    for the table references that has not been resolved requests for mdl_locks
+    has to be set.
   */
-  for (TABLE_LIST *tbl= spec_tables;
-       tbl;
-       tbl= tbl->next_global)
+  lex->only_cte_resolution= old_lex->only_cte_resolution;
+  if (lex->resolve_references_to_cte(lex->query_tables,
+                                     lex->query_tables_last))
   {
-    if (!tbl->with)
-      tbl->with= with_select->find_table_def_in_with_clauses(tbl);
-    if (tbl == spec_tables_tail)
-      break;
-  }
-  if (check_table_access(thd, SELECT_ACL, spec_tables, FALSE, UINT_MAX, FALSE))
+    res= NULL;
     goto err;
+  }
 
-  lex->sphead= NULL;    // in order not to delete lex->sphead
+ lex->sphead= NULL;    // in order not to delete lex->sphead
   lex_end(lex);
 err:
-  if (arena)
-    thd->restore_active_arena(arena, &backup);
   thd->lex= old_lex;
   return res;
 }
@@ -1105,59 +1316,6 @@ With_element *st_select_lex::find_table_def_in_with_clauses(TABLE_LIST *table)
 }
 
 
-/**
-   @brief
-     Set the specifying unit in this reference to a with table  
-     
-  @details  
-    The method assumes that the given element with_elem defines the table T
-    this table reference refers to.
-    If this is the first reference to T the method just sets its specification
-    in the field 'derived' as the unit that yields T. Otherwise the method  
-    first creates a clone specification and sets rather this clone in this field.
- 
-  @retval
-    false   on success
-    true    on failure
-*/    
-
-bool TABLE_LIST::set_as_with_table(THD *thd, With_element *with_elem)
-{
-  if (table)
-  {
-    /*
-      This table was prematurely identified as a temporary table.
-      We correct it here, but it's not a nice solution in the case
-      when the temporary table with this name is not used anywhere
-      else in the query.
-    */
-    thd->mark_tmp_table_as_free_for_reuse(table);
-    table= 0;
-  }
-  with= with_elem;
-  schema_table= NULL;
-  if (!with_elem->is_referenced() || with_elem->is_recursive)
-  {
-    derived= with_elem->spec;
-    if (derived != select_lex->master_unit() &&
-        !with_elem->is_recursive &&
-        !is_with_table_recursive_reference())
-    {
-       derived->move_as_slave(select_lex);
-    }
-  }
-  else 
-  {
-    if(!(derived= with_elem->clone_parsed_spec(thd, this)))
-      return true;
-  }
-  derived->first_select()->set_linkage(DERIVED_TABLE_TYPE);
-  select_lex->add_statistics(derived);
-  with_elem->inc_references();
-  return false;
-}
-
-
 bool TABLE_LIST::is_recursive_with_table()
 {
   return with && with->is_recursive;
@@ -1257,7 +1415,7 @@ bool st_select_lex::check_unrestricted_recursive(bool only_standard_compliant)
   if (only_standard_compliant && with_elem->is_unrestricted())
   {
     my_error(ER_NOT_STANDARD_COMPLIANT_RECURSIVE,
-	     MYF(0), with_elem->query_name->str);
+             MYF(0), with_elem->get_name_str());
     return true;
   }
 
@@ -1457,7 +1615,7 @@ void With_clause::print(String *str, enum_query_type query_type)
 
 void With_element::print(String *str, enum_query_type query_type)
 {
-  str->append(query_name);
+  str->append(get_name());
   if (column_list.elements)
   {
     List_iterator_fast<LEX_CSTRING> li(column_list);