Bug#36542023: Simplify the find_field function interfaces

The existing functions for resolving column references are still
present, but interfaces have been simplified and made more consistent.

Error handling is separated out and an error is now indicated with
a true function return, as usual.

Generally, a successful resolver function call will return one out of
three responses:
- column was not found, or
- column was found and resolved to a field reference, or
- column was found and resolved to an indirect reference (Item_ref).
The arguments could be simpler, but this subdivision is there for
efficiency: a field reference is usually used to resolve an Item_field
object, however it may also be used to populate some indirect
reference object (Item_ref) later on. Thus, it makes sense to keep the
field reference until we know what to do with it.

Interfaces for iterating over natural join columns and view columns have
been changed from operating on Item pointers to Item_ident pointers,
since they only work with field objects and reference objects.
This simplified the code, since some asserts and casts could be removed.

The old slightly confusing enum find_item_error_report_type for
reporting or ignoring certain error conditions has been replaced with
a bitmask specifying which errors to possibly return.

Old asserts marked 'WL#6570 remove-after-qa' are deleted.

The patch also fixes the problem in bug 36704815 by not checking
derived tables when the column reference contains a database name.
New tests are added for this case.

Specific changes, per function:

find_field_in_tables()

- Irrelevant argument register_tree_change is deleted.
- Improved asserts for valid column name search.
- Shortcut for item->m_table_ref != nullptr is removed.

find_field_in_table_ref()

- Irrelevant arguments register_tree_change and cached_field_index_ptr
  are deleted.

find_field_in_table()

- Irrelevant arguments field_index_ptr, register_tree_change and
  actual_table have been deleted.
- Improved asserts of input arguments (Table_ref argument).
- Removed check for empty database name.

find_field_in_table_sef()

- Only cosmetic changes.

find_field_in_view()

- Irrelevant arguments register_tree_change and actual_table are
  deleted.
- The possible alias name of a column is passed explicitly, instead of
  being picked up from the "ref" argument.
- ps_arena_holder is removed since this function is only called during
  resolving.
- Successful outcome is reported as field not found, base table field
  found or reference found.

find_field_in_natural_join()

- Irrelevant arguments register_tree_change and actual_table are
  deleted.
- ps_arena_holder was deleted, since function is only called by resolver.
- Explicit call to nj_col->table_field->fix_fields() was irrelevant and
  has been removed.

Item_field::fix_fields()

- Special call to rf->fix_fields() was irrelevant and hence deleted.

Item_field::fix_outer_field()

- A new argument "complete" is used to signal that the object returned
  from this function is fully resolved.
- The field_found variable is removed since it is no longer used.
- The field upward_lookup is replaced with has_outer_context, since it
  better describes what is being tested. (It is used to report error
  in the case that Item_field::fix_fields() did not find a field
  reference and there are no possible outer references to resolve).

Item_ref::fix_fields()

- Mostly unchanged, only adapted to new call interfaces.
- ps_arena_holder was deleted, since function is only called by resolver.
- Some redundant code is removed and substituted with asserts.

Change-Id: I11c51c25f30c4f85abefa9d326c2336bc31bb7d7

Author: roylyseng

mysql-test/include/with_non_recursive.inc

@@ -226,15 +226,16 @@ FROM qn;
 --error ER_PARSE_ERROR
 with test.qn as (select "with") select * from test.qn;
 
---echo # Adding a db. prefix to a field still resolves to the QN; it's a bit awkward as
---echo # the QN doesn't belong to a db, but it's the same with derived table:
+--echo # Adding a database prefix to a field does not resolve to the QN:
+--error ER_BAD_FIELD_ERROR
 select test.qn.a from (select "with" as a) qn;
 
---echo # OTOH, db. prefix in FROM doesn't resolve to QN, which is good
+--echo # database prefix in FROM does not resolve to QN:
 with qn as (select "with") select * from qn;
 with qn as (select "with") select * from test.qn;
 with qn as (select "with" as a) select a from qn;
 with qn as (select "with" as a) select qn.a from qn;
+--error ER_BAD_FIELD_ERROR
 with qn as (select "with" as a) select test.qn.a from qn;
 with qn as (select "with" as a) select a from test.qn;
 with qn as (select "with" as a) select qn.a from test.qn;

mysql-test/r/derived.result

@@ -1,11 +1,15 @@
-drop table if exists t1,t2,t3;
-select * from (select 2 from DUAL) b;
+select * from (select 2 from DUAL) AS b;
 2
 2
-SELECT 1 as a FROM (SELECT 1 UNION SELECT a) b;
+SELECT 1 as a FROM (SELECT 1 UNION SELECT a) AS b;
 ERROR 42S22: Unknown column 'a' in 'field list'
-SELECT 1 as a FROM (SELECT a UNION SELECT 1) b;
+SELECT 1 as a FROM (SELECT a UNION SELECT 1) AS b;
 ERROR 42S22: Unknown column 'a' in 'field list'
+select dt.a from (select 1 as a) as dt;
+a
+1
+select test.dt.a from (select 1 as a) as dt;
+ERROR 42S22: Unknown column 'test.dt.a' in 'field list'
 CREATE TABLE t1 (a int not null, b char (10) not null);
 insert into t1 values(1,'a'),(2,'b'),(3,'c'),(3,'c');
 CREATE TABLE t2 (a int not null, b char (10) not null);

mysql-test/r/with_non_recursive.result

@@ -244,12 +244,10 @@ inner	outer
 # Qualified name isn't allowed after WITH:
 with test.qn as (select "with") select * from test.qn;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '.qn as (select "with") select * from test.qn' at line 1
-# Adding a db. prefix to a field still resolves to the QN; it's a bit awkward as
-# the QN doesn't belong to a db, but it's the same with derived table:
+# Adding a database prefix to a field does not resolve to the QN:
 select test.qn.a from (select "with" as a) qn;
-a
-with
-# OTOH, db. prefix in FROM doesn't resolve to QN, which is good
+ERROR 42S22: Unknown column 'test.qn.a' in 'field list'
+# database prefix in FROM does not resolve to QN:
 with qn as (select "with") select * from qn;
 with
 with
@@ -263,8 +261,7 @@ with qn as (select "with" as a) select qn.a from qn;
 a
 with
 with qn as (select "with" as a) select test.qn.a from qn;
-a
-with
+ERROR 42S22: Unknown column 'test.qn.a' in 'field list'
 with qn as (select "with" as a) select a from test.qn;
 a
 tmp
@@ -1355,12 +1352,10 @@ inner	outer
 # Qualified name isn't allowed after WITH:
 with test.qn as (select "with") select * from test.qn;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '.qn as (select "with") select * from test.qn' at line 1
-# Adding a db. prefix to a field still resolves to the QN; it's a bit awkward as
-# the QN doesn't belong to a db, but it's the same with derived table:
+# Adding a database prefix to a field does not resolve to the QN:
 select test.qn.a from (select "with" as a) qn;
-a
-with
-# OTOH, db. prefix in FROM doesn't resolve to QN, which is good
+ERROR 42S22: Unknown column 'test.qn.a' in 'field list'
+# database prefix in FROM does not resolve to QN:
 with qn as (select "with") select * from qn;
 with
 with
@@ -1374,8 +1369,7 @@ with qn as (select "with" as a) select qn.a from qn;
 a
 with
 with qn as (select "with" as a) select test.qn.a from qn;
-a
-with
+ERROR 42S22: Unknown column 'test.qn.a' in 'field list'
 with qn as (select "with" as a) select a from test.qn;
 a
 tmp

mysql-test/t/derived.test

@@ -7,16 +7,16 @@
 --source include/force_myisam_default.inc
 --source include/have_myisam.inc
 
-# Initialize
---disable_warnings
-drop table if exists t1,t2,t3;
---enable_warnings
+select * from (select 2 from DUAL) AS b;
+-- error ER_BAD_FIELD_ERROR
+SELECT 1 as a FROM (SELECT 1 UNION SELECT a) AS b;
+-- error ER_BAD_FIELD_ERROR
+SELECT 1 as a FROM (SELECT a UNION SELECT 1) AS b;
+
+select dt.a from (select 1 as a) as dt;
+-- error ER_BAD_FIELD_ERROR
+select test.dt.a from (select 1 as a) as dt;
 
-select * from (select 2 from DUAL) b;
--- error 1054
-SELECT 1 as a FROM (SELECT 1 UNION SELECT a) b;
--- error 1054
-SELECT 1 as a FROM (SELECT a UNION SELECT 1) b;
 CREATE TABLE t1 (a int not null, b char (10) not null);
 insert into t1 values(1,'a'),(2,'b'),(3,'c'),(3,'c');
 CREATE TABLE t2 (a int not null, b char (10) not null);

sql/auth/sql_authorization.cc

@@ -2674,20 +2674,22 @@ int mysql_table_grant(THD *thd, Table_ref *table_list,
           return true; /* purecov: inspected */
       }
       while ((column = column_iter++)) {
-        uint unused_field_idx = NO_FIELD_INDEX;
-        Table_ref *dummy;
-        Field *f = find_field_in_table_ref(
-            thd, table_list, column->column.ptr(), column->column.length(),
-            column->column.ptr(), nullptr, nullptr, nullptr,
-            // check that we have the
-            // to-be-granted privilege:
-            column->rights, false, &unused_field_idx, false, &dummy);
-        if (f == (Field *)nullptr) {
+        Field *field;
+        Find_field_result found;
+        if (find_field_in_table_ref(
+                thd, table_list, column->column.ptr(), column->column.length(),
+                column->column.ptr(), nullptr, nullptr,
+                // check that we have the to-be-granted privilege:
+                column->rights, false, &found, &field, nullptr)) {
+          return true;
+        }
+        assert(found != VIEW_FIELD_FOUND);
+        if (found != BASE_FIELD_FOUND) {
           my_error(ER_BAD_FIELD_ERROR, MYF(0), column->column.c_ptr(),
                    table_list->alias);
           return true;
         }
-        if (f == (Field *)-1) return true;
+        assert(field != nullptr);
         column_priv |= column->rights;
       }
       close_mysql_tables(thd);