mirror/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-01-16 20:12:31 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions
mariadb/sql/sql_cte.cc
Igor Babaev 7a29ca2776 Fixed the bug mdev-12563. 
The bug happened when the specification of a recursive CTE had
no recursive references at the top level of the specification.
In this case the regular processing of derived table references
of the select containing a non-recursive reference to this
recursive CTE misses handling the specification unit.
At the preparation stage any non-recursive reference to a
recursive CTE must be handled after the preparation of the
specification unit for this CTE. So we have to force this
preparation when regular handling of derived tables does not
do it.
2017-04-28 21:59:11 -07:00

1383 lines
42 KiB
C++
Raw Blame History

#include "sql_class.h"
#include "sql_lex.h"
#include "sql_cte.h"
#include "sql_view.h" // for make_valid_column_names
#include "sql_parse.h"
#include "sql_select.h"
/**
@brief
Add a new element to this with clause
@param elem The with element to add to this with clause
@details
The method adds the with element 'elem' to the elements
in this with clause. The method reports an error if
the number of the added element exceeds the value
of the constant max_number_of_elements_in_with_clause.
@retval
true if an error is reported
false otherwise
*/
bool With_clause::add_with_element(With_element *elem)
{
if (with_list.elements == max_number_of_elements_in_with_clause)
{
my_error(ER_TOO_MANY_DEFINITIONS_IN_WITH_CLAUSE, MYF(0));
return true;
}
elem->owner= this;
elem->number= with_list.elements;
elem->spec->with_element= elem;
with_list.link_in_list(elem, &elem->next);
return false;
}
/**
@brief
Check dependencies between tables defined in a list of with clauses
@param
with_clauses_list Pointer to the first clause in the list
@details
For each with clause from the given list the procedure finds all
dependencies between tables defined in the clause by calling the
method With_clause::checked_dependencies.
Additionally, based on the info collected by this method the procedure
finds anchors for each recursive definition and moves them at the head
of the definition.
@retval
false on success
true on failure
*/
bool check_dependencies_in_with_clauses(With_clause *with_clauses_list)
{
for (With_clause *with_clause= with_clauses_list;
with_clause;
with_clause= with_clause->next_with_clause)
{
if (with_clause->check_dependencies())
return true;
if (with_clause->check_anchors())
return true;
with_clause->move_anchors_ahead();
}
return false;
}
/**
@brief
Check dependencies between tables defined in this with clause
@details
The method performs the following for this with clause:
- checks that there are no definitions of the tables with the same name
- for each table T defined in this with clause looks for the tables
from the same with clause that are used in the query that specifies T
and set the dependencies of T on these tables in a bitmap.
- builds the transitive closure of the above direct dependencies
to find out all recursive definitions.
@retval
true if an error is reported
false otherwise
*/
bool With_clause::check_dependencies()
{
if (dependencies_are_checked)
return false;
/*
Look for for definitions with the same query name.
When found report an error and return true immediately.
For each table T defined in this with clause look for all other tables
from the same with clause that are used in the specification of T.
For each such table set the dependency bit in the dependency map of
the with element for T.
*/
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
for (With_element *elem= with_list.first;
elem != with_elem;
elem= elem->next)
{
if (my_strcasecmp(system_charset_info, with_elem->query_name->str,
elem->query_name->str) == 0)
{
my_error(ER_DUP_QUERY_NAME, MYF(0), with_elem->query_name->str);
return true;
}
}
if (with_elem->check_dependencies_in_spec())
return true;
}
/* Build the transitive closure of the direct dependencies found above */
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
with_elem->derived_dep_map= with_elem->base_dep_map;
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
table_map with_elem_map= with_elem->get_elem_map();
for (With_element *elem= with_list.first; elem; elem= elem->next)
{
if (elem->derived_dep_map & with_elem_map)
elem->derived_dep_map |= with_elem->derived_dep_map;
}
}
/*
Mark those elements where tables are defined with direct or indirect
recursion.
*/
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (with_elem->derived_dep_map & with_elem->get_elem_map())
with_elem->is_recursive= true;
}
dependencies_are_checked= true;
return false;
}
/*
This structure describes an element of the stack of embedded units.
The stack is used when looking for a definition of a table in
with clauses. The definition can be found only in the scopes
of the with clauses attached to the units from the stack.
The with clauses are looked through from starting from the top
element of the stack.
*/
struct st_unit_ctxt_elem
{
st_unit_ctxt_elem *prev; // the previous element of the stack
st_select_lex_unit *unit;
};
/**
@brief
Find the dependencies of this element on its siblings in its specification
@details
For each table reference ref(T) from the FROM list of every select sl
immediately contained in the specification query of this element this
method searches for the definition of T in the the with clause which
this element belongs to. If such definition is found then the dependency
on it is set in sl->with_dep and in this->base_dep_map.
*/
bool With_element::check_dependencies_in_spec()
{
for (st_select_lex *sl= spec->first_select(); sl; sl= sl->next_select())
{
st_unit_ctxt_elem ctxt0= {NULL, owner->owner};
st_unit_ctxt_elem ctxt1= {&ctxt0, spec};
check_dependencies_in_select(sl, &ctxt1, false, &sl->with_dep);
base_dep_map|= sl->with_dep;
}
return false;
}
/**
@brief
Search for the definition of a table among the elements of this with clause
@param table The reference to the table that is looked for
@param barrier The barrier with element for the search
@details
The function looks through the elements of this with clause trying to find
the definition of the given table. When it encounters the element with
the same query name as the table's name it returns this element. If no
such definitions are found the function returns NULL.
@retval
found with element if the search succeeded
NULL - otherwise
*/
With_element *With_clause::find_table_def(TABLE_LIST *table,
With_element *barrier)
{
for (With_element *with_elem= with_list.first;
with_elem != barrier;
with_elem= with_elem->next)
{
if (my_strcasecmp(system_charset_info, with_elem->query_name->str,
table->table_name) == 0)
{
table->set_derived();
return with_elem;
}
}
return NULL;
}
/**
@brief
Search for the definition of a table in with clauses
@param tbl The reference to the table that is looked for
@param ctxt The context describing in what with clauses of the upper
levels the table has to be searched for.
@details
The function looks for the definition of the table tbl in the definitions
of the with clauses from the upper levels specified by the parameter ctxt.
When it encounters the element with the same query name as the table's name
it returns this element. If no such definitions are found the function
returns NULL.
@retval
found with element if the search succeeded
NULL - otherwise
*/
With_element *find_table_def_in_with_clauses(TABLE_LIST *tbl,
st_unit_ctxt_elem *ctxt)
{
With_element *barrier= NULL;
for (st_unit_ctxt_elem *unit_ctxt_elem= ctxt;
unit_ctxt_elem;
unit_ctxt_elem= unit_ctxt_elem->prev)
{
st_select_lex_unit *unit= unit_ctxt_elem->unit;
With_clause *with_clause= unit->with_clause;
if (with_clause &&
(tbl->with= with_clause->find_table_def(tbl, barrier)))
return tbl->with;
barrier= NULL;
if (unit->with_element && !unit->with_element->get_owner()->with_recursive)
{
/*
This unit is the specification if the with element unit->with_element.
The with element belongs to a with clause without the specifier RECURSIVE.
So when searching for the matching definition of tbl this with clause must
be looked up to this with element
*/
barrier= unit->with_element;
}
}
return NULL;
}
/**
@brief
Find the dependencies of this element on its siblings in a select
@param sl The select where to look for the dependencies
@param ctxt The structure specifying the scope of the definitions
of the with elements of the upper levels
@param in_sbq if true mark dependencies found in subqueries in
this->sq_dep_map
@param dep_map IN/OUT The bit where to mark the found dependencies
@details
For each table reference ref(T) from the FROM list of the select sl
the method searches in with clauses for the definition of the table T.
If the found definition belongs to the same with clause as this with
element then the method set dependency on T in the in/out parameter
dep_map, add if required - in this->sq_dep_map.
The parameter ctxt describes the proper context for the search
of the definition of T.
*/
void With_element::check_dependencies_in_select(st_select_lex *sl,
st_unit_ctxt_elem *ctxt,
bool in_subq,
table_map *dep_map)
{
With_clause *with_clause= sl->get_with_clause();
for (TABLE_LIST *tbl= sl->table_list.first; tbl; tbl= tbl->next_local)
{
if (tbl->derived || tbl->nested_join)
continue;
tbl->with_internal_reference_map= 0;
/*
If there is a with clause attached to the unit containing sl
look first for the definition of tbl in this with clause.
If such definition is not found there look in the with
clauses of the upper levels.
If the definition of tbl is found somewhere in with clauses
then tbl->with is set to point to this definition
*/
if (with_clause && !tbl->with)
tbl->with= with_clause->find_table_def(tbl, NULL);
if (!tbl->with)
tbl->with= find_table_def_in_with_clauses(tbl, ctxt);
if (tbl->with && tbl->with->owner== this->owner)
{
/*
The found definition T of tbl belongs to the same
with clause as this with element. In this case:
- set the dependence on T in the bitmap dep_map
- set tbl->with_internal_reference_map with
the bitmap for this definition
- set the dependence on T in the bitmap this->sq_dep_map
if needed
*/
*dep_map|= tbl->with->get_elem_map();
tbl->with_internal_reference_map= get_elem_map();
if (in_subq)
sq_dep_map|= tbl->with->get_elem_map();
else
top_level_dep_map|= tbl->with->get_elem_map();
}
}
/* Now look for the dependencies in the subqueries of sl */
st_select_lex_unit *inner_unit= sl->first_inner_unit();
for (; inner_unit; inner_unit= inner_unit->next_unit())
check_dependencies_in_unit(inner_unit, ctxt, in_subq, dep_map);
}
/**
@brief
Find a recursive reference to this with element in subqueries of a select
@param sel The select in whose subqueries the reference
to be looked for
@details
The function looks for a recursive reference to this with element in
subqueries of select sl. When the first such reference is found
it is returned as the result.
The function assumes that the identification of all CTE references
has been performed earlier.
@retval
Pointer to the found recursive reference if the search succeeded
NULL - otherwise
*/
TABLE_LIST *With_element::find_first_sq_rec_ref_in_select(st_select_lex *sel)
{
TABLE_LIST *rec_ref= NULL;
st_select_lex_unit *inner_unit= sel->first_inner_unit();
for (; inner_unit; inner_unit= inner_unit->next_unit())
{
st_select_lex *sl= inner_unit->first_select();
for (; sl; sl= sl->next_select())
{
for (TABLE_LIST *tbl= sl->table_list.first; tbl; tbl= tbl->next_local)
{
if (tbl->derived || tbl->nested_join)
continue;
if (tbl->with && tbl->with->owner== this->owner &&
(tbl->with_internal_reference_map & mutually_recursive))
{
rec_ref= tbl;
return rec_ref;
}
}
if ((rec_ref= find_first_sq_rec_ref_in_select(sl)))
return rec_ref;
}
}
return 0;
}
/**
@brief
Find the dependencies of this element on its siblings in a unit
@param unit The unit where to look for the dependencies
@param ctxt The structure specifying the scope of the definitions
of the with elements of the upper levels
@param in_sbq if true mark dependencies found in subqueries in
this->sq_dep_map
@param dep_map IN/OUT The bit where to mark the found dependencies
@details
This method searches in the unit 'unit' for the the references in FROM
lists of all selects contained in this unit and in the with clause
attached to this unit that refer to definitions of tables from the
same with clause as this element.
If such definitions are found then the dependencies on them are
set in the in/out parameter dep_map and optionally in this->sq_dep_map.
The parameter ctxt describes the proper context for the search.
*/
void With_element::check_dependencies_in_unit(st_select_lex_unit *unit,
st_unit_ctxt_elem *ctxt,
bool in_subq,
table_map *dep_map)
{
if (unit->with_clause)
check_dependencies_in_with_clause(unit->with_clause, ctxt, in_subq, dep_map);
in_subq |= unit->item != NULL;
st_unit_ctxt_elem unit_ctxt_elem= {ctxt, unit};
st_select_lex *sl= unit->first_select();
for (; sl; sl= sl->next_select())
{
check_dependencies_in_select(sl, &unit_ctxt_elem, in_subq, dep_map);
}
}
/**
@brief
Find the dependencies of this element on its siblings in a with clause
@param witt_clause The with clause where to look for the dependencies
@param ctxt The structure specifying the scope of the definitions
of the with elements of the upper levels
@param in_sbq if true mark dependencies found in subqueries in
this->sq_dep_map
@param dep_map IN/OUT The bit where to mark the found dependencies
@details
This method searches in the with_clause for the the references in FROM
lists of all selects contained in the specifications of the with elements
from this with_clause that refer to definitions of tables from the
same with clause as this element.
If such definitions are found then the dependencies on them are
set in the in/out parameter dep_map and optionally in this->sq_dep_map.
The parameter ctxt describes the proper context for the search.
*/
void
With_element::check_dependencies_in_with_clause(With_clause *with_clause,
st_unit_ctxt_elem *ctxt,
bool in_subq,
table_map *dep_map)
{
for (With_element *with_elem= with_clause->with_list.first;
with_elem;
with_elem= with_elem->next)
{
check_dependencies_in_unit(with_elem->spec, ctxt, in_subq, dep_map);
}
}
/**
@brief
Find mutually recursive with elements and check that they have ancors
@details
This method performs the following:
- for each recursive with element finds all mutually recursive with it
- links each group of mutually recursive with elements into a ring chain
- checks that every group of mutually recursive with elements contains
at least one anchor
- checks that after removing any with element with anchor the remaining
with elements mutually recursive with the removed one are not recursive
anymore
@retval
true if an error is reported
false otherwise
*/
bool With_clause::check_anchors()
{
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (!with_elem->is_recursive)
continue;
/*
It with_elem is recursive with element find all elements mutually recursive
with it (any recursive element is mutually recursive with itself). Mark all
these elements in the bitmap->mutually_recursive. Also link all these
elements into a ring chain.
*/
if (!with_elem->next_mutually_recursive)
{
With_element *last_mutually_recursive= with_elem;
table_map with_elem_dep= with_elem->derived_dep_map;
table_map with_elem_map= with_elem->get_elem_map();
for (With_element *elem= with_elem; elem; elem= elem->next)
{
if (!elem->is_recursive)
continue;
if (elem == with_elem ||
((elem->derived_dep_map & with_elem_map) &&
(with_elem_dep & elem->get_elem_map())))
{
elem->next_mutually_recursive= with_elem;
last_mutually_recursive->next_mutually_recursive= elem;
last_mutually_recursive= elem;
with_elem->mutually_recursive|= elem->get_elem_map();
}
}
for (With_element *elem= with_elem->next_mutually_recursive;
elem != with_elem;
elem= elem->next_mutually_recursive)
elem->mutually_recursive= with_elem->mutually_recursive;
}
/*
For each select from the specification of 'with_elem' check whether
it is an anchor i.e. does not depend on any with elements mutually
recursive with 'with_elem".
*/
for (st_select_lex *sl= with_elem->spec->first_select();
sl;
sl= sl->next_select())
{
if (with_elem->is_anchor(sl))
{
with_elem->with_anchor= true;
break;
}
}
}
/*
Check that for any group of mutually recursive with elements
- there is at least one anchor
- after removing any with element with anchor the remaining with elements
mutually recursive with the removed one are not recursive anymore
*/
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (!with_elem->is_recursive)
continue;
if (!with_elem->with_anchor)
{
/*
Check that the other with elements mutually recursive with 'with_elem'
contain at least one anchor.
*/
With_element *elem= with_elem;
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
{
if (elem->with_anchor)
break;
}
if (elem == with_elem)
{
my_error(ER_RECURSIVE_WITHOUT_ANCHORS, MYF(0),
with_elem->query_name->str);
return true;
}
}
else
{
/* 'with_elem' is a with element with an anchor */
With_element *elem= with_elem;
/*
For the other with elements mutually recursive with 'with_elem'
set dependency bits between those elements in the field work_dep_map
and build transitive closure of these dependencies
*/
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
elem->work_dep_map= elem->base_dep_map & elem->mutually_recursive;
elem= with_elem;
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
{
table_map elem_map= elem->get_elem_map();
With_element *el= with_elem;
while ((el= el->get_next_mutually_recursive()) != with_elem)
{
if (el->work_dep_map & elem_map)
el->work_dep_map|= elem->work_dep_map;
}
}
/* If the transitive closure displays any cycle report an arror */
elem= with_elem;
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
{
if (elem->work_dep_map & elem->get_elem_map())
{
my_error(ER_UNACCEPTABLE_MUTUAL_RECURSION, MYF(0),
with_elem->query_name->str);
return true;
}
}
}
}
return false;
}
/**
@brief
Move anchors at the beginning of the specifications for with elements
@details
This method moves anchors at the beginning of the specifications for
all recursive with elements.
*/
void With_clause::move_anchors_ahead()
{
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (with_elem->is_recursive)
with_elem->move_anchors_ahead();
}
}
/**
@brief
Move anchors at the beginning of the specification of this with element
@details
If the specification of this with element contains anchors the method
moves them at the very beginning of the specification.
Additionally for the other selects of the specification if none of them
contains a recursive reference to this with element or a mutually recursive
one the method looks for the first such reference in the first recursive
select and set a pointer to it in this->sq_rec_ref.
*/
void With_element::move_anchors_ahead()
{
st_select_lex *next_sl;
st_select_lex *new_pos= spec->first_select();
st_select_lex *last_sl;
new_pos->linkage= UNION_TYPE;
for (st_select_lex *sl= new_pos; sl; sl= next_sl)
{
next_sl= sl->next_select();
if (is_anchor(sl))
{
sl->move_node(new_pos);
new_pos= sl->next_select();
}
else if (!sq_rec_ref && no_rec_ref_on_top_level())
{
sq_rec_ref= find_first_sq_rec_ref_in_select(sl);
DBUG_ASSERT(sq_rec_ref != NULL);
}
last_sl= sl;
}
if (spec->union_distinct)
spec->union_distinct= last_sl;
first_recursive= new_pos;
}
/**
@brief
Perform context analysis for all unreferenced tables defined in with clause
@param thd The context of the statement containing this with clause
@details
For each unreferenced table T defined in this with clause the method
calls the method With_element::prepare_unreferenced that performs
context analysis of the element with the definition of T.
@retval
false If context analysis does not report any error
true Otherwise
*/
bool With_clause::prepare_unreferenced_elements(THD *thd)
{
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (!with_elem->is_referenced() && with_elem->prepare_unreferenced(thd))
return true;
}
return false;
}
/**
@brief
Save the specification of the given with table as a string
@param thd The context of the statement containing this with element
@param spec_start The beginning of the specification in the input string
@param spec_end The end of the specification in the input string
@details
The method creates for a string copy of the specification used in this
element. The method is called when the element is parsed. The copy may be
used to create clones of the specification whenever they are needed.
@retval
false on success
true on failure
*/
bool With_element::set_unparsed_spec(THD *thd, char *spec_start, char *spec_end)
{
unparsed_spec.length= spec_end - spec_start;
unparsed_spec.str= (char*) thd->memdup(spec_start, unparsed_spec.length+1);
unparsed_spec.str[unparsed_spec.length]= '\0';
if (!unparsed_spec.str)
{
my_error(ER_OUTOFMEMORY, MYF(ME_FATALERROR),
static_cast<int>(unparsed_spec.length));
return true;
}
return false;
}
/**
@brief
Create a clone of the specification for the given with table
@param thd The context of the statement containing this with element
@param with_table The reference to the table defined in this element for which
the clone is created.
@details
The method creates a clone of the specification used in this element.
The clone is created for the given reference to the table defined by
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.
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.
@note
Clones is created only for not first references to tables defined in
the with clause. They are necessary for merged specifications because
the optimizer handles any such specification as independent on the others.
When a table defined in the with clause is materialized in a temporary table
one could do without specification clones. However in this case they
are created as well, because currently different table references to a
the same temporary table cannot share the same definition structure.
@retval
pointer to the built clone if succeeds
NULL - otherwise
*/
st_select_lex_unit *With_element::clone_parsed_spec(THD *thd,
TABLE_LIST *with_table)
{
LEX *lex;
st_select_lex_unit *res= NULL;
Query_arena backup;
Query_arena *arena= thd->activate_stmt_arena_if_needed(&backup);
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;
if (parser_state.init(thd, unparsed_spec.str, unparsed_spec.length))
goto err;
lex_start(thd);
with_select= &lex->select_lex;
with_select->select_number= ++thd->select_number;
parse_status= parse_sql(thd, &parser_state, 0);
if (parse_status)
goto err;
spec_tables= lex->query_tables;
spec_tables_tail= 0;
for (TABLE_LIST *tbl= spec_tables;
tbl;
tbl= tbl->next_global)
{
tbl->grant.privilege= with_table->grant.privilege;
spec_tables_tail= tbl;
}
if (spec_tables)
{
if (with_table->next_global)
{
spec_tables_tail->next_global= with_table->next_global;
with_table->next_global->prev_global= &spec_tables_tail->next_global;
}
else
{
old_lex->query_tables_last= &spec_tables_tail->next_global;
}
spec_tables->prev_global= &with_table->next_global;
with_table->next_global= spec_tables;
}
res= &lex->unit;
res->set_with_clause(owner);
lex->unit.include_down(with_table->select_lex);
lex->unit.set_slave(with_select);
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));
lex_end(lex);
err:
if (arena)
thd->restore_active_arena(arena, &backup);
thd->lex= old_lex;
return res;
}
/**
@brief
Rename columns of the unit derived from the spec of this with element
@param thd The context of the statement containing the with element
@param unit The specification of the with element or its clone
@details
The method assumes that the parameter unit is either specification itself
of this with element or a clone of this specification. The looks through
the column list in this with element. It reports an error if the cardinality
of this list differs from the cardinality of select lists in 'unit'.
Otherwise it renames the columns of the first select list and sets the flag
unit->column_list_is_processed to true preventing renaming columns for the
second time.
@retval
true if an error was reported
false otherwise
*/
bool
With_element::rename_columns_of_derived_unit(THD *thd,
st_select_lex_unit *unit)
{
if (unit->columns_are_renamed)
return false;
st_select_lex *select= unit->first_select();
if (column_list.elements) // The column list is optional
{
List_iterator_fast<Item> it(select->item_list);
List_iterator_fast<LEX_STRING> nm(column_list);
Item *item;
LEX_STRING *name;
if (column_list.elements != select->item_list.elements)
{
my_error(ER_WITH_COL_WRONG_LIST, MYF(0));
return true;
}
/* Rename the columns of the first select in the unit */
while ((item= it++, name= nm++))
{
item->set_name(thd, name->str, (uint) name->length, system_charset_info);
item->is_autogenerated_name= false;
}
}
else
make_valid_column_names(thd, select->item_list);
unit->columns_are_renamed= true;
return false;
}
/**
@brief
Perform context analysis the definition of an unreferenced table
@param thd The context of the statement containing this with element
@details
The method assumes that this with element contains the definition
of a table that is not used anywhere. In this case one has to check
that context conditions are met.
@retval
true if an error was reported
false otherwise
*/
bool With_element::prepare_unreferenced(THD *thd)
{
bool rc= false;
st_select_lex *first_sl= spec->first_select();
/* Prevent name resolution for field references out of with elements */
for (st_select_lex *sl= first_sl;
sl;
sl= sl->next_select())
sl->context.outer_context= 0;
thd->lex->context_analysis_only|= CONTEXT_ANALYSIS_ONLY_DERIVED;
if (!spec->prepared &&
(spec->prepare(thd, 0, 0) ||
rename_columns_of_derived_unit(thd, spec) ||
check_duplicate_names(thd, first_sl->item_list, 1)))
rc= true;
thd->lex->context_analysis_only&= ~CONTEXT_ANALYSIS_ONLY_DERIVED;
return rc;
}
bool With_element::is_anchor(st_select_lex *sel)
{
return !(mutually_recursive & sel->with_dep);
}
/**
@brief
Search for the definition of the given table referred in this select node
@param table reference to the table whose definition is searched for
@details
The method looks for the definition of the table whose reference is occurred
in the FROM list of this select node. First it searches for it in the
with clause attached to the unit this select node belongs to. If such a
definition is not found then the embedding units are looked through.
@retval
pointer to the found definition if the search has been successful
NULL - otherwise
*/
With_element *st_select_lex::find_table_def_in_with_clauses(TABLE_LIST *table)
{
st_select_lex_unit *master_unit= NULL;
With_element *found= NULL;
for (st_select_lex *sl= this;
sl;
sl= master_unit->outer_select())
{
With_element *with_elem= sl->get_with_element();
/*
If sl->master_unit() is the spec of a with element then the search for
a definition was already done by With_element::check_dependencies_in_spec
and it was unsuccesful. Yet for units cloned from the spec it has not
been done yet.
*/
if (with_elem && sl->master_unit() == with_elem->spec)
break;
With_clause *with_clause=sl->get_with_clause();
if (with_clause)
{
With_element *barrier= with_clause->with_recursive ? NULL : with_elem;
if ((found= with_clause->find_table_def(table, barrier)))
break;
}
master_unit= sl->master_unit();
/* Do not look for the table's definition beyond the scope of the view */
if (master_unit->is_view)
break;
}
return found;
}
/**
@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;
if (!with_elem->is_referenced() || with_elem->is_recursive)
derived= with_elem->spec;
else
{
if(!(derived= with_elem->clone_parsed_spec(thd, this)))
return true;
derived->with_element= with_elem;
}
with_elem->inc_references();
return false;
}
bool TABLE_LIST::is_recursive_with_table()
{
return with && with->is_recursive;
}
/*
A reference to a with table T is recursive if it occurs somewhere
in the query specifying T or in the query specifying one of the tables
mutually recursive with T.
*/
bool TABLE_LIST::is_with_table_recursive_reference()
{
return (with_internal_reference_map &&
(with->get_mutually_recursive() & with_internal_reference_map));
}
/*
Specifications of with tables with recursive table references
in non-mergeable derived tables are not allowed in this
implementation.
*/
/*
We say that the specification of a with table T is restricted
if all below is true.
1. Any immediate select of the specification contains at most one
recursive table reference taking into account table references
from mergeable derived tables.
2. Any recursive table reference is not an inner operand of an
outer join operation used in an immediate select of the
specification.
3. Any immediate select from the specification of T does not
contain aggregate functions.
4. The specification of T does not contain recursive table references.
If the specification of T is not restricted we call the corresponding
with element unrestricted.
The SQL standards allows only with elements with restricted specification.
By default we comply with the standards here.
Yet we allow unrestricted specification if the status variable
'standards_compliant_cte' set to 'off'(0).
*/
/**
@brief
Check if this select makes the including specification unrestricted
@param
only_standards_compliant true if the system variable
'standards_compliant_cte' is set to 'on'
@details
This method checks whether the conditions 1-4 (see the comment above)
are satisfied for this select. If not then mark this element as
unrestricted and report an error if 'only_standards_compliant' is true.
@retval
true if an error is reported
false otherwise
*/
bool st_select_lex::check_unrestricted_recursive(bool only_standard_compliant)
{
With_element *with_elem= get_with_element();
if (!with_elem ||!with_elem->is_recursive)
{
/*
If this select is not from the specifiocation of a with elememt or
if this not a recursive with element then there is nothing to check.
*/
return false;
}
/* Check conditions 1-2 for restricted specification*/
table_map unrestricted= 0;
table_map encountered= 0;
if (with_elem->check_unrestricted_recursive(this,
unrestricted,
encountered))
return true;
with_elem->get_owner()->add_unrestricted(unrestricted);
/* Check conditions 3-4 for restricted specification*/
if (with_sum_func ||
(with_elem->contains_sq_with_recursive_reference()))
with_elem->get_owner()->add_unrestricted(
with_elem->get_mutually_recursive());
/* Report an error on unrestricted specification if this is required */
if (only_standard_compliant && with_elem->is_unrestricted())
{
my_error(ER_NOT_STANDARD_COMPLIANT_RECURSIVE,
MYF(0), with_elem->query_name->str);
return true;
}
return false;
}
/**
@brief
Check if a select from the spec of this with element is partially restricted
@param
sel select from the specification of this element where to check
whether conditions 1-2 are satisfied
unrestricted IN/OUT bitmap where to mark unrestricted specs
encountered IN/OUT bitmap where to mark encountered recursive references
@details
This method checks whether the conditions 1-2 (see the comment above)
are satisfied for the select sel.
This method is called recursively for derived tables.
@retval
true if an error is reported
false otherwise
*/
bool With_element::check_unrestricted_recursive(st_select_lex *sel,
table_map &unrestricted,
table_map &encountered)
{
/* Check conditions 1 for restricted specification*/
List_iterator<TABLE_LIST> ti(sel->leaf_tables);
TABLE_LIST *tbl;
while ((tbl= ti++))
{
st_select_lex_unit *unit= tbl->get_unit();
if (unit)
{
if(!tbl->is_with_table())
{
if (check_unrestricted_recursive(unit->first_select(),
unrestricted,
encountered))
return true;
}
if (!(tbl->is_recursive_with_table() && unit->with_element->owner == owner))
continue;
With_element *with_elem= unit->with_element;
if (encountered & with_elem->get_elem_map())
unrestricted|= with_elem->mutually_recursive;
else
encountered|= with_elem->get_elem_map();
}
}
for (With_element *with_elem= owner->with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (!with_elem->is_recursive && (unrestricted & with_elem->get_elem_map()))
continue;
if (encountered & with_elem->get_elem_map())
{
uint cnt= 0;
table_map encountered_mr= encountered & with_elem->mutually_recursive;
for (table_map map= encountered_mr >> with_elem->number;
map != 0;
map>>= 1)
{
if (map & 1)
{
if (cnt)
{
unrestricted|= with_elem->mutually_recursive;
break;
}
else
cnt++;
}
}
}
}
/* Check conditions 2 for restricted specification*/
ti.rewind();
while ((tbl= ti++))
{
if (!tbl->is_with_table_recursive_reference())
continue;
for (TABLE_LIST *tab= tbl; tab; tab= tab->embedding)
{
if (tab->outer_join & (JOIN_TYPE_LEFT | JOIN_TYPE_RIGHT))
{
unrestricted|= mutually_recursive;
break;
}
}
}
return false;
}
/**
@brief
Check subqueries with recursive table references from FROM list of this select
@details
For each recursive table reference from the FROM list of this select
this method checks:
- whether this reference is within a materialized derived table and
if so it report an error
- whether this reference is within a subquery and if so it set a flag
in this subquery that disallows some optimization strategies for
this subquery.
@retval
true if an error is reported
false otherwise
*/
bool st_select_lex::check_subqueries_with_recursive_references()
{
st_select_lex_unit *sl_master= master_unit();
List_iterator<TABLE_LIST> ti(leaf_tables);
TABLE_LIST *tbl;
while ((tbl= ti++))
{
if (!(tbl->is_with_table_recursive_reference() && sl_master->item))
continue;
With_element *with_elem= tbl->with;
bool check_embedding_materialized_derived= true;
for (st_select_lex *sl= this; sl; sl= sl_master->outer_select())
{
sl_master= sl->master_unit();
if (with_elem->get_owner() == sl_master->with_clause)
check_embedding_materialized_derived= false;
if (check_embedding_materialized_derived && !sl_master->with_element &&
sl_master->derived && sl_master->derived->is_materialized_derived())
{
my_error(ER_REF_TO_RECURSIVE_WITH_TABLE_IN_DERIVED,
MYF(0), with_elem->query_name->str);
return true;
}
if (!sl_master->item)
continue;
Item_subselect *subq= (Item_subselect *) sl_master->item;
subq->with_recursive_reference= true;
subq->register_as_with_rec_ref(tbl->with);
}
}
return false;
}
/**
@brief
Print this with clause
@param str Where to print to
@param query_type The mode of printing
@details
The method prints a string representation of this clause in the
string str. The parameter query_type specifies the mode of printing.
*/
void With_clause::print(String *str, enum_query_type query_type)
{
/*
Any with clause contains just definitions of CTE tables.
No data expansion is applied to these definitions.
*/
query_type= (enum_query_type) (query_type | QT_NO_DATA_EXPANSION);
str->append(STRING_WITH_LEN("with "));
if (with_recursive)
str->append(STRING_WITH_LEN("recursive "));
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (with_elem != with_list.first)
str->append(", ");
with_elem->print(str, query_type);
}
}
/**
@brief
Print this with element
@param str Where to print to
@param query_type The mode of printing
@details
The method prints a string representation of this with element in the
string str. The parameter query_type specifies the mode of printing.
*/
void With_element::print(String *str, enum_query_type query_type)
{
str->append(query_name);
str->append(STRING_WITH_LEN(" as "));
str->append('(');
spec->print(str, query_type);
str->append(')');
}
bool With_element::instantiate_tmp_tables()
{
List_iterator_fast<TABLE> li(rec_result->rec_tables);
TABLE *rec_table;
while ((rec_table= li++))
{
if (!rec_table->is_created() &&
instantiate_tmp_table(rec_table,
rec_result->tmp_table_param.keyinfo,
rec_result->tmp_table_param.start_recinfo,
&rec_result->tmp_table_param.recinfo,
0))
return true;
rec_table->file->extra(HA_EXTRA_WRITE_CACHE);
rec_table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
}
return false;
}
Reference in a new issue View git blame Copy permalink