mirror of https://gitee.com/bigwinds/arangodb
239 lines
9.1 KiB
JavaScript
239 lines
9.1 KiB
JavaScript
/*jslint indent: 2, nomen: true, maxlen: 100, sloppy: true, vars: true, white: true, plusplus: true */
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/*global require */
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////////////////////////////////////////////////////////////////////////////////
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/// @brief query explain actions
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///
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/// @file
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///
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/// DISCLAIMER
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///
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/// Copyright 2012 triagens GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is triAGENS GmbH, Cologne, Germany
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///
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/// @author Jan Steemann
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/// @author Copyright 2012, triAGENS GmbH, Cologne, Germany
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////////////////////////////////////////////////////////////////////////////////
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var actions = require("org/arangodb/actions");
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var ArangoError = require("org/arangodb").ArangoError;
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var ERRORS = require("internal").errors;
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var EXPLAIN = require("internal").AQL_EXPLAIN;
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// -----------------------------------------------------------------------------
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// --SECTION-- global variables
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// -----------------------------------------------------------------------------
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////////////////////////////////////////////////////////////////////////////////
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/// @addtogroup ArangoAPI
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/// @{
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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/// @brief explain a query and return information about it
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///
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/// @RESTHEADER{POST /_api/explain,explains a query}
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///
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/// @RESTBODYPARAM{body,json,required}
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/// The query string needs to be passed in the attribute `query` of a JSON
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/// object as the body of the POST request. If the query references any bind
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/// variables, these must also be passed in the attribute `bindVars`.
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///
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/// @RESTDESCRIPTION
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///
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/// To explain how an AQL query would be executed on the server, the query string
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/// can be sent to the server via an HTTP POST request. The server will then validate
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/// the query and create an execution plan for it, but will not execute it.
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///
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/// The execution plan that is returned by the server can be used to estimate the
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/// probable performance of an AQL query. Though the actual performance will depend
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/// on many different factors, the execution plan normally can give some good hint
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/// on the amount of work the server needs to do in order to actually run the query.
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///
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/// The top-level statements will appear in the result in the same order in which
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/// they have been used in the original query. Each result element has at most the
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/// following attributes:
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/// - `id`: the row number of the top-level statement, starting at 1
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/// - `type`: the type of the top-level statement (e.g. `for`, `return` ...)
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/// - `loopLevel`: the nesting level of the top-level statement, starting at 1
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/// Depending on the type of top-level statement, there might be other attributes
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/// providing additional information, for example, if and which indexed will be
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/// used.
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/// Many top-level statements will provide an `expression` attribute that
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/// contains data about the expression they operate on. This is true for `FOR`,
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/// `FILTER`, `SORT`, `COLLECT`, and `RETURN` statements. The
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/// `expression` attribute has the following sub-attributes:
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/// - `type`: the type of the expression. Some possible values are:
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/// - `collection`: an iteration over documents from a collection. The
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/// `value` attribute will then contain the collection name. The `extra`
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/// attribute will contain information about if and which index is used when
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/// accessing the documents from the collection. If no index is used, the
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/// `accessType` sub-attribute of the `extra` attribute will have the
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/// value `all`, otherwise it will be `index`.
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/// - `list`: a list of dynamic values. The `value` attribute will contain the
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/// list elements.
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/// - `const list`: a list of constant values. The `value` attribute will contain the
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/// list elements.
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/// - `reference`: a reference to another variable. The `value` attribute
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/// will contain the name of the variable that is referenced.
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///
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/// Please note that the structure of the explain result data might change in future
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/// versions of ArangoDB without further notice and without maintaining backwards
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/// compatibility.
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///
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/// @RESTRETURNCODES
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///
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/// @RESTRETURNCODE{200}
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/// If the query is valid, the server will respond with `HTTP 200` and
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/// return a list of the individual query execution steps in the `"plan"`
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/// attribute of the response.
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///
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/// @RESTRETURNCODE{400}
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/// The server will respond with `HTTP 400` in case of a malformed request,
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/// or if the query contains a parse error. The body of the response will
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/// contain the error details embedded in a JSON object.
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/// Omitting bind variables if the query references any will result also result
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/// in an `HTTP 400` error.
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///
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/// @RESTRETURNCODE{404}
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/// The server will respond with `HTTP 404` in case a non-existing collection is
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/// accessed in the query.
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///
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/// @EXAMPLES
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///
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/// Valid query:
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///
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/// @EXAMPLE_ARANGOSH_RUN{RestExplainValid}
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/// var url = "/_api/explain";
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/// var cn = "products";
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/// db._drop(cn);
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/// db._create(cn, { waitForSync: true });
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/// body = '{ ' +
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/// '"query" : "FOR p IN products FILTER p.id == @id LIMIT 2 RETURN p.name", ' +
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/// '"bindVars": { "id" : 3 } ' +
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/// '}';
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///
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/// var response = logCurlRequest('POST', url, body);
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///
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/// assert(response.code === 200);
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///
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/// logJsonResponse(response);
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/// @END_EXAMPLE_ARANGOSH_RUN
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///
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/// Invalid query:
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///
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/// @EXAMPLE_ARANGOSH_RUN{RestExplainInvalid}
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/// var url = "/_api/explain";
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/// var cn = "products";
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/// db._drop(cn);
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/// db._create(cn, { waitForSync: true });
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/// body = '{ "query" : "FOR p IN products FILTER p.id == @id LIMIT 2 RETURN p.n" }';
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///
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/// var response = logCurlRequest('POST', url, body);
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///
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/// assert(response.code === 400);
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///
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/// logJsonResponse(response);
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/// @END_EXAMPLE_ARANGOSH_RUN
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///
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/// The data returned in the `plan` attribute of the result contains one
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/// element per AQL top-level statement (i.e. `FOR`, `RETURN`,
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/// `FILTER` etc.). If the query optimiser removed some unnecessary statements,
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/// the result might also contain less elements than there were top-level
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/// statements in the AQL query.
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/// The following example shows a query with a non-sensible filter condition that
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/// the optimiser has removed so that there are less top-level statements:
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///
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/// @EXAMPLE_ARANGOSH_RUN{RestExplainEmpty}
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/// var url = "/_api/explain";
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/// var cn = "products";
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/// db._drop(cn);
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/// db._create(cn, { waitForSync: true });
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/// body = '{ "query" : "FOR i IN [ 1, 2, 3 ] FILTER 1 == 2 RETURN i" }';
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///
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/// var response = logCurlRequest('POST', url, body);
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///
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/// assert(response.code === 200);
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///
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/// logJsonResponse(response);
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/// @END_EXAMPLE_ARANGOSH_RUN
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////////////////////////////////////////////////////////////////////////////////
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function post_api_explain (req, res) {
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if (req.suffix.length !== 0) {
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actions.resultNotFound(req,
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res,
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ERRORS.errors.ERROR_HTTP_NOT_FOUND.code,
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ERRORS.errors.ERROR_HTTP_NOT_FOUND.message);
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return;
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}
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var json = actions.getJsonBody(req, res);
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if (json === undefined) {
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return;
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}
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var result = EXPLAIN(json.query, json.bindVars);
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if (result instanceof Error) {
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actions.resultException(req, res, result, undefined, false);
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return;
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}
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result = { "plan" : result };
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actions.resultOk(req, res, actions.HTTP_OK, result);
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}
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// -----------------------------------------------------------------------------
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// --SECTION-- initialiser
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// -----------------------------------------------------------------------------
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////////////////////////////////////////////////////////////////////////////////
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/// @brief explain gateway
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////////////////////////////////////////////////////////////////////////////////
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actions.defineHttp({
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url : "_api/explain",
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context : "api",
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callback : function (req, res) {
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try {
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switch (req.requestType) {
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case actions.POST:
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post_api_explain(req, res);
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break;
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default:
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actions.resultUnsupported(req, res);
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}
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}
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catch (err) {
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actions.resultException(req, res, err, undefined, false);
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}
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}
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});
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////////////////////////////////////////////////////////////////////////////////
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/// @}
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////////////////////////////////////////////////////////////////////////////////
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// Local Variables:
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// mode: outline-minor
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// outline-regexp: "^\\(/// @brief\\|/// @addtogroup\\|// --SECTION--\\|/// @page\\|/// @}\\)"
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// End:
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