MDEV-32220 sql_yacc.yy: unify the drop_routine rule

- Removing two copies of the drop_routine.
  Adding a shared and much simplified version.

- Removing LEX metods:
      bool stmt_drop_function(const DDL_options_st &options,
                              const Lex_ident_sys_st &db,
                              const Lex_ident_sys_st &name);

      bool stmt_drop_function(const DDL_options_st &options,
                              const Lex_ident_sys_st &name);

      bool stmt_drop_procedure(const DDL_options_st &options,
                               sp_name *name);

  The code inside the methods was very similar.
  Adding one method instead:

      bool stmt_drop_routine(const Sp_handler *sph,
                          const DDL_options_st &options,
                          const Lex_ident_sys_st &db,
                          const Lex_ident_sys_st &name);

- Adding a new virtual method Sp_handler:sqlcom_drop().
  It helped to unify the code inside the new stmt_drop_routine().

sql/sp.h

@@ -157,6 +157,7 @@ class Sp_handler
   }
   virtual enum_sp_type type() const= 0;
   virtual LEX_CSTRING type_lex_cstring() const= 0;
+  virtual enum_sql_command sqlcom_drop() const= 0;
   virtual LEX_CSTRING empty_body_lex_cstring(sql_mode_t mode) const
   {
     static LEX_CSTRING m_empty_body= {STRING_WITH_LEN("???")};
@@ -256,6 +257,7 @@ class Sp_handler_procedure: public Sp_handler
     static LEX_CSTRING m_type_str= { STRING_WITH_LEN("PROCEDURE")};
     return m_type_str;
   }
+  enum_sql_command sqlcom_drop() const { return SQLCOM_DROP_PROCEDURE; }
   LEX_CSTRING empty_body_lex_cstring(sql_mode_t mode) const;
   const char *show_create_routine_col1_caption() const
   {
@@ -306,6 +308,7 @@ class Sp_handler_function: public Sp_handler
     static LEX_CSTRING m_type_str= { STRING_WITH_LEN("FUNCTION")};
     return m_type_str;
   }
+  enum_sql_command sqlcom_drop() const { return SQLCOM_DROP_FUNCTION; }
   LEX_CSTRING empty_body_lex_cstring(sql_mode_t mode) const;
   const char *show_create_routine_col1_caption() const
   {
@@ -375,6 +378,7 @@ class Sp_handler_package_spec: public Sp_handler_package
     static LEX_CSTRING m_type_str= {STRING_WITH_LEN("PACKAGE")};
     return m_type_str;
   }
+  enum_sql_command sqlcom_drop() const { return SQLCOM_DROP_PACKAGE; }
   LEX_CSTRING empty_body_lex_cstring(sql_mode_t mode) const
   {
     static LEX_CSTRING m_empty_body= {STRING_WITH_LEN("BEGIN END")};
@@ -408,6 +412,7 @@ class Sp_handler_package_body: public Sp_handler_package
     static LEX_CSTRING m_type_str= {STRING_WITH_LEN("PACKAGE BODY")};
     return m_type_str;
   }
+  enum_sql_command sqlcom_drop() const { return SQLCOM_DROP_PACKAGE_BODY; }
   LEX_CSTRING empty_body_lex_cstring(sql_mode_t mode) const
   {
     static LEX_CSTRING m_empty_body= {STRING_WITH_LEN("BEGIN END")};
@@ -441,6 +446,7 @@ class Sp_handler_trigger: public Sp_handler
     static LEX_CSTRING m_type_str= { STRING_WITH_LEN("TRIGGER")};
     return m_type_str;
   }
+  enum_sql_command sqlcom_drop() const { return SQLCOM_DROP_TRIGGER; }
   MDL_key::enum_mdl_namespace get_mdl_type() const
   {
     DBUG_ASSERT(0);

sql/sql_lex.cc

@@ -11487,54 +11487,68 @@ bool LEX::stmt_create_stored_function_start(const DDL_options_st &options,
 }
 
 
-bool LEX::stmt_drop_function(const DDL_options_st &options,
-                             const Lex_ident_sys_st &db,
-                             const Lex_ident_sys_st &name)
+/*
+  Process a drop routine statement:
+    DROP {FUNCTION|PROCEDURE|PACKAGE|PACKAGE BODY}
+    [IF NOT EXISTS ] [db.]name;
+
+  @param sph     - The stored routine
+  @param options - The IF EXISTS clause
+  @param db      - The database name.
+                   It can be {NULL,0}, which means the routine name
+                   is not qualified with the database name.
+  @param name    - The routine name
+  @returns       - false ok success, true on error.
+*/
+bool LEX::stmt_drop_routine(const Sp_handler *sph,
+                            const DDL_options_st &options,
+                            const Lex_ident_sys_st &db,
+                            const Lex_ident_sys_st &name)
 {
-  DBUG_ASSERT(db.str);
   DBUG_ASSERT(name.str);
-  const Lex_ident_db db_int= thd->to_ident_db_internal_with_error(db);
-  if (unlikely(!db_int.str))
-    return true;
-
   if (unlikely(sphead))
   {
-    my_error(ER_SP_NO_DROP_SP, MYF(0), "FUNCTION");
+    my_error(ER_SP_NO_DROP_SP, MYF(0), sph->type_lex_cstring().str);
     return true;
   }
-  set_command(SQLCOM_DROP_FUNCTION, options);
-  spname= new (thd->mem_root) sp_name(&db_int, &name, true);
-  return spname == NULL;
-}
-
-
-bool LEX::stmt_drop_function(const DDL_options_st &options,
-                             const Lex_ident_sys_st &name)
-{
-  LEX_CSTRING db= {0, 0};
-  if (unlikely(sphead))
-  {
-    my_error(ER_SP_NO_DROP_SP, MYF(0), "FUNCTION");
+  if (check_routine_name(&name))
     return true;
+  enum_sql_command sqlcom= sph->sqlcom_drop();
+  LEX_CSTRING db_int= {0, 0};
+  if (db.str)
+  {
+    // An explicit database name is given
+    if (!(db_int= thd->to_ident_db_internal_with_error(db)).str)
+      return true;
   }
-  if (thd->db.str && unlikely(copy_db_to(&db)))
-    return true;
-  set_command(SQLCOM_DROP_FUNCTION, options);
-  spname= new (thd->mem_root) sp_name(&db, &name, false);
-  return spname == NULL;
-}
-
-
-bool LEX::stmt_drop_procedure(const DDL_options_st &options,
-                              sp_name *name)
-{
-  if (unlikely(sphead))
+  else if (thd->db.str || sqlcom != SQLCOM_DROP_FUNCTION)
   {
-    my_error(ER_SP_NO_DROP_SP, MYF(0), "PROCEDURE");
-    return true;
+    /*
+      There is no an explicit database name in the DROP statement.
+      Two cases are possible:
+      a. The current database is not NULL.
+         copy_db_to() copies the current database to db_int.
+      b. The current database is NULL and the command is either of these:
+         - DROP PACKAGE
+         - DROP PACKAGE BODY
+         - DROP PROCEDURE
+         copy_db_to() raises ER_NO_DB_ERROR.
+    */
+    if (copy_db_to(&db_int))
+      return true;
   }
-  set_command(SQLCOM_DROP_PROCEDURE, options);
-  spname= name;
+  else
+  {
+    /*
+      This is a "DROP FUNCTION name" statement.
+      There is no an explicit database name given.
+      The current database is not set.
+      It can still be a valid DROP FUNCTION - for an UDF.
+      Keep db_int=={NULL,0}.
+    */
+  }
+  set_command(sqlcom, options);
+  spname= new (thd->mem_root) sp_name(&db_int, &name, db.str != NULL);
   return false;
 }
 

sql/sql_lex.h

@@ -4852,15 +4852,10 @@ struct LEX: public Query_tables_list
                                 Item_result return_type,
                                 const LEX_CSTRING &soname);
 
-  bool stmt_drop_function(const DDL_options_st &options,
-                          const Lex_ident_sys_st &db,
-                          const Lex_ident_sys_st &name);
-
-  bool stmt_drop_function(const DDL_options_st &options,
-                          const Lex_ident_sys_st &name);
-
-  bool stmt_drop_procedure(const DDL_options_st &options,
-                           sp_name *name);
+  bool stmt_drop_routine(const Sp_handler *sph,
+                         const DDL_options_st &options,
+                         const Lex_ident_sys_st &db,
+                         const Lex_ident_sys_st &name);
 
   bool stmt_alter_function_start(sp_name *name);
   bool stmt_alter_procedure_start(sp_name *name);

sql/sql_yacc.yy

@@ -3016,6 +3016,20 @@ sp_handler:
         ;
 
 
+drop_routine:
+          DROP sp_handler opt_if_exists ident '.' ident
+          {
+            if (Lex->stmt_drop_routine($2, $3, $4, $6))
+              MYSQL_YYABORT;
+          }
+        | DROP sp_handler opt_if_exists ident
+          {
+            if (Lex->stmt_drop_routine($2, $3, Lex_ident_sys(), $4))
+              MYSQL_YYABORT;
+          }
+        ;
+
+
 sp_name:
           ident '.' ident
           {
@@ -18441,25 +18455,6 @@ sp_tail_standalone:
           }
         ;
 
-drop_routine:
-          DROP FUNCTION_SYM opt_if_exists ident '.' ident
-          {
-            if (Lex->stmt_drop_function($3, $4, $6))
-              MYSQL_YYABORT;
-          }
-        | DROP FUNCTION_SYM opt_if_exists ident
-          {
-            if (Lex->stmt_drop_function($3, $4))
-              MYSQL_YYABORT;
-          }
-        | DROP PROCEDURE_SYM opt_if_exists sp_name
-          {
-            if (Lex->stmt_drop_procedure($3, $4))
-              MYSQL_YYABORT;
-          }
-        ;
-
-
 create_routine:
           create_or_replace definer_opt PROCEDURE_SYM opt_if_not_exists
           {
@@ -19346,40 +19341,6 @@ sp_tail_standalone:
           }
         ;
 
-drop_routine:
-          DROP FUNCTION_SYM opt_if_exists ident '.' ident
-          {
-            if (Lex->stmt_drop_function($3, $4, $6))
-              MYSQL_YYABORT;
-          }
-        | DROP FUNCTION_SYM opt_if_exists ident
-          {
-            if (Lex->stmt_drop_function($3, $4))
-              MYSQL_YYABORT;
-          }
-        | DROP PROCEDURE_SYM opt_if_exists sp_name
-          {
-            if (Lex->stmt_drop_procedure($3, $4))
-              MYSQL_YYABORT;
-          }
-        | DROP PACKAGE_ORACLE_SYM opt_if_exists sp_name
-          {
-            LEX *lex= Lex;
-            lex->set_command(SQLCOM_DROP_PACKAGE, $3);
-            if (unlikely(lex->sphead))
-              my_yyabort_error((ER_SP_NO_DROP_SP, MYF(0), "PACKAGE"));
-            lex->spname= $4;
-          }
-        | DROP PACKAGE_ORACLE_SYM BODY_ORACLE_SYM opt_if_exists sp_name
-          {
-            LEX *lex= Lex;
-            lex->set_command(SQLCOM_DROP_PACKAGE_BODY, $4);
-            if (unlikely(lex->sphead))
-              my_yyabort_error((ER_SP_NO_DROP_SP, MYF(0), "PACKAGE BODY"));
-            lex->spname= $5;
-          }
-        ;
-
 
 create_routine:
           create_or_replace definer_opt PROCEDURE_SYM opt_if_not_exists