Refactor parts of Item_func_sp into Item_sp

In preparation for implementing custom aggregate functions, refactor
the common code between regular stored functions and aggregate stored
functions. This includes:

* initialising SP result field
* executing a SP
* access checks

In addition, refactor sp_head::execute_function to take two extra
parameters, a function rcontext and a Query_arena. These two paremeters
were initially initialised and destroyed within
sp_head::execute_function, but for aggregate stored functions we will
require control over their lifetime. The owner of these objects now
becomes Item_sp.

Signed-off-by: Vicențiu Ciorbaru <vicentiu@mariadb.org>

sql/item.cc

@@ -2730,6 +2730,237 @@ Item* Item_func_or_sum::build_clone(THD *thd)
   return copy;
 }
 
+Item_sp::Item_sp(THD *thd, Name_resolution_context *context_arg,
+                 sp_name *name_arg) :
+  context(context_arg), m_name(name_arg), m_sp(NULL), func_ctx(NULL),
+  sp_result_field(NULL)
+{
+  dummy_table= (TABLE*) thd->calloc(sizeof(TABLE) + sizeof(TABLE_SHARE));
+  dummy_table->s= (TABLE_SHARE*) (dummy_table + 1);
+  memset(&sp_mem_root, 0, sizeof(sp_mem_root));
+}
+
+const char *
+Item_sp::func_name(THD *thd) const
+{
+  /* Calculate length to avoid reallocation of string for sure */
+  uint len= (((m_name->m_explicit_name ? m_name->m_db.length : 0) +
+              m_name->m_name.length)*2 + //characters*quoting
+             2 +                         // ` and `
+             (m_name->m_explicit_name ?
+              3 : 0) +                   // '`', '`' and '.' for the db
+             1 +                         // end of string
+             ALIGN_SIZE(1));             // to avoid String reallocation
+  String qname((char *)alloc_root(thd->mem_root, len), len,
+               system_charset_info);
+
+  qname.length(0);
+  if (m_name->m_explicit_name)
+  {
+    append_identifier(thd, &qname, m_name->m_db.str, m_name->m_db.length);
+    qname.append('.');
+  }
+  append_identifier(thd, &qname, m_name->m_name.str, m_name->m_name.length);
+  return qname.c_ptr_safe();
+}
+
+void
+Item_sp::cleanup()
+{
+  delete sp_result_field;
+  sp_result_field= NULL;
+  m_sp= NULL;
+  delete func_ctx;
+  func_ctx= NULL;
+  free_root(&sp_mem_root, MYF(0));
+  dummy_table->alias.free();
+}
+
+/**
+  @brief Checks if requested access to function can be granted to user.
+    If function isn't found yet, it searches function first.
+    If function can't be found or user don't have requested access
+    error is raised.
+
+  @param thd thread handler
+
+  @return Indication if the access was granted or not.
+  @retval FALSE Access is granted.
+  @retval TRUE Requested access can't be granted or function doesn't exists.
+
+*/
+bool
+Item_sp::sp_check_access(THD *thd)
+{
+  DBUG_ENTER("Item_sp::sp_check_access");
+  DBUG_ASSERT(m_sp);
+  DBUG_RETURN(m_sp->check_execute_access(thd));
+}
+
+/**
+  @brief Execute function & store value in field.
+
+  @return Function returns error status.
+  @retval FALSE on success.
+  @retval TRUE if an error occurred.
+*/
+bool Item_sp::execute(THD *thd, bool *null_value, Item **args, uint arg_count)
+{
+  if (execute_impl(thd, args, arg_count))
+  {
+    *null_value= 1;
+    context->process_error(thd);
+    if (thd->killed)
+      thd->send_kill_message();
+    return true;
+  }
+
+  /* Check that the field (the value) is not NULL. */
+
+  *null_value= sp_result_field->is_null();
+  return (*null_value);
+}
+
+/**
+   @brief Execute function and store the return value in the field.
+
+   @note This function was intended to be the concrete implementation of
+    the interface function execute. This was never realized.
+
+   @return The error state.
+   @retval FALSE on success
+   @retval TRUE if an error occurred.
+*/
+bool
+Item_sp::execute_impl(THD *thd, Item **args, uint arg_count)
+{
+  Sub_statement_state statement_state;
+  Security_context *save_security_ctx= thd->security_ctx;
+  enum enum_sp_data_access access=
+    (m_sp->daccess() == SP_DEFAULT_ACCESS) ?
+     SP_DEFAULT_ACCESS_MAPPING : m_sp->daccess();
+
+  DBUG_ENTER("Item_sp::execute_impl");
+
+  if (context->security_ctx)
+  {
+    /* Set view definer security context */
+    thd->security_ctx= context->security_ctx;
+  }
+
+  if (sp_check_access(thd))
+  {
+    thd->security_ctx= save_security_ctx;
+    DBUG_RETURN(TRUE);
+  }
+
+  /*
+    Throw an error if a non-deterministic function is called while
+    statement-based replication (SBR) is active.
+  */
+
+  if (!m_sp->detistic() && !trust_function_creators &&
+      (access == SP_CONTAINS_SQL || access == SP_MODIFIES_SQL_DATA) &&
+      (mysql_bin_log.is_open() &&
+       thd->variables.binlog_format == BINLOG_FORMAT_STMT))
+  {
+    my_error(ER_BINLOG_UNSAFE_ROUTINE, MYF(0));
+    thd->security_ctx= save_security_ctx;
+    DBUG_RETURN(TRUE);
+  }
+
+  /*
+    Disable the binlogging if this is not a SELECT statement. If this is a
+    SELECT, leave binlogging on, so execute_function() code writes the
+    function call into binlog.
+  */
+  thd->reset_sub_statement_state(&statement_state, SUB_STMT_FUNCTION);
+
+  init_sql_alloc(&sp_mem_root, MEM_ROOT_BLOCK_SIZE, 0, MYF(0));
+  Query_arena call_arena(&sp_mem_root, Query_arena::STMT_INITIALIZED_FOR_SP);
+
+  bool err_status= m_sp->execute_function(thd, args, arg_count,
+                                          sp_result_field, &func_ctx,
+                                          &call_arena);
+  /* Free Items allocated during function execution. */
+  delete func_ctx;
+  func_ctx= NULL;
+  call_arena.free_items();
+  free_root(&sp_mem_root, MYF(0));
+  memset(&sp_mem_root, 0, sizeof(sp_mem_root));
+
+  thd->restore_sub_statement_state(&statement_state);
+
+  thd->security_ctx= save_security_ctx;
+  DBUG_RETURN(err_status);
+}
+
+
+/**
+  @brief Initialize the result field by creating a temporary dummy table
+    and assign it to a newly created field object. Meta data used to
+    create the field is fetched from the sp_head belonging to the stored
+    proceedure found in the stored procedure functon cache.
+
+  @note This function should be called from fix_fields to init the result
+    field. It is some what related to Item_field.
+
+  @see Item_field
+
+  @param thd A pointer to the session and thread context.
+
+  @return Function return error status.
+  @retval TRUE is returned on an error
+  @retval FALSE is returned on success.
+*/
+
+bool
+Item_sp::init_result_field(THD *thd, sp_head *sp, uint max_length,
+                           uint maybe_null, bool *null_value, LEX_CSTRING *name)
+{
+  DBUG_ENTER("Item_sp::init_result_field");
+
+  DBUG_ASSERT(m_sp == NULL);
+  DBUG_ASSERT(sp_result_field == NULL);
+
+  if (!(m_sp= sp))
+  {
+    my_missing_function_error (m_name->m_name, ErrConvDQName(m_name).ptr());
+    context->process_error(thd);
+    DBUG_RETURN(TRUE);
+  }
+
+  /*
+     A Field needs to be attached to a Table.
+     Below we "create" a dummy table by initializing
+     the needed pointers.
+   */
+  dummy_table->alias.set("", 0, table_alias_charset);
+  dummy_table->in_use= thd;
+  dummy_table->copy_blobs= TRUE;
+  dummy_table->s->table_cache_key= empty_clex_str;
+  dummy_table->s->table_name= empty_clex_str;
+  dummy_table->maybe_null= maybe_null;
+
+  if (!(sp_result_field= m_sp->create_result_field(max_length, name,
+                                                   dummy_table)))
+   DBUG_RETURN(TRUE);
+
+  if (sp_result_field->pack_length() > sizeof(result_buf))
+  {
+    void *tmp;
+    if (!(tmp= thd->alloc(sp_result_field->pack_length())))
+      DBUG_RETURN(TRUE);
+    sp_result_field->move_field((uchar*) tmp);
+  }
+  else
+    sp_result_field->move_field(result_buf);
+
+  sp_result_field->null_ptr= (uchar *) null_value;
+  sp_result_field->null_bit= 1;
+
+  DBUG_RETURN(FALSE);
+}
 
 /**
   @brief

sql/item.h

@@ -4471,6 +4471,34 @@ class Item_func_or_sum: public Item_result_field,
   Item* build_clone(THD *thd);
 };
 
+class sp_head;
+class sp_name;
+struct st_sp_security_context;
+
+class Item_sp
+{
+public:
+  Name_resolution_context *context;
+  sp_name *m_name;
+  sp_head *m_sp;
+  TABLE *dummy_table;
+  uchar result_buf[64];
+  sp_rcontext *func_ctx;
+  MEM_ROOT sp_mem_root;
+
+  /*
+     The result field of the stored function.
+  */
+  Field *sp_result_field;
+  Item_sp(THD *thd, Name_resolution_context *context_arg, sp_name *name_arg);
+  const char *func_name(THD *thd) const;
+  void cleanup();
+  bool sp_check_access(THD *thd);
+  bool execute(THD *thd, bool *null_value, Item **args, uint arg_count);
+  bool execute_impl(THD *thd, Item **args, uint arg_count);
+  bool init_result_field(THD *thd, sp_head *sp, uint max_length,
+                         uint maybe_null, bool *null_value, LEX_CSTRING *name);
+};
 
 class Item_ref :public Item_ident
 {