| // Copyright 2015 The Vanadium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package query_functions describes SyncQL's built-in functions. |
| // |
| // This package is called by the query_checker package to check that |
| // a function exists and is being passed the correct number of |
| // arguments and, if possible, the correct types of arguments. If |
| // the function can be executed at check time (because |
| // the function has no args or because the args are all literals (or |
| // (recursively) other functions that can be executed at check time), |
| // the function is executed at check time and the result of the function |
| // is subsituted for the function in the AST. |
| // |
| // If the function cannot be executed at check time, it is executed by |
| // the query package once for each candicate row (in the case of function |
| // calls in the where clause) or selected row (in the case of function calls |
| // in the select clause). |
| // |
| // It is expected that functions will be grouped in some way into separate |
| // files (e.g., string functions are in str_funcs.go). |
| // |
| // Functions must be listed in the functions map in query_functions.go. |
| // Each entry is a function struct which contains the following fields: |
| // |
| // argTypes []query_parser.OperandType |
| // The arguments expected. If the argument count is wrong, |
| // the checker will produce an error. The types are |
| // informational only as the function itself is required |
| // to attempt to coerce the args to the correct type or |
| // return an error. |
| // hasVarArgs bool |
| // True if, in addition to any types listed in argTypes, the function |
| // can take additional (optional) args. |
| // varArgsType The type of the additional (optional) args. |
| // returnType query_parser.OperandType |
| // The return type of the function, for informational purposes |
| // only. |
| // funcAddr queryFunc |
| // The address of the query function. |
| // If the function cannot complete to success, it must return an error and the |
| // argument responsible for the error. |
| // checkArgsAddr checkArgsFunc |
| // The address of a function to check args at checker time. |
| // This function should check any arguments that it can at checker time. |
| // It can check literals. Note: if all args are literals, the function itself |
| // is called at checker time rather than this function. |
| // DO NOT sepecify a checkArgsAddr if all that is to be checked is the number |
| // and types of args. These checks are standard. |
| package query_functions |
