EOS数据库操作

目录

新增

新增内容往往用到emplace构造函数，来进行数据库对象的新增。

  1. void test_da::create(account_name user, string title, string content)
  2.     {
  3.         require_auth( user ); //验证权限
  4.         das datable( _self, user);　//定义数据库对象
  5.         datable.emplace(user, [&]( da & d){
  6.             d.title = title;
  7.             d.content = content;
  8.             d.post_id = datable.available_primary_key();
  9.             d.poster = user;
  10.         });　//数据库内容创建
  11.     }

这里需要注意的是：

  1. 定义数据库对象，其中第一个参数是合约的拥有者_self，第二个变量就是数据库的payer，也就是数据库是谁的，数据库存储在谁的账户下。
  2. emplace函数接收两个参数，一个payer,和一个lamada表达式。这个结构是固定的。

那么我们现在来看一下我们的test_da类是怎么定义的。 .hpp　

  1. class test_da : public contract {
  2.      public:
  3.            test_da( account_name self ):contract(self){}
  5.            // @abi action
  6.            void create(account_name user, string title, string content);
  8.      private:
  9.            // @abi table data i64
  10.            struct da {
  11.                  uint64_t     post_id;
  12.                  account_name poster;
  13.                  string       title;
  14.                  string       content;
  16.                  uint64_t primary_key()const { return post_id; }
  17.                  account_name get_poster() const { return poster; }
  19.                  EOSLIB_SERIALIZE(da, (post_id)(poster)(title)(content))
  20.            };
  21.            typedef eosio::multi_index<N(data), da, indexed_by<N(byposter), const_mem_fun<da, account_name, &da::get_poster>> > das;
  22.   };
  23. } /// namespace eosio
  1. 所有的智能合约都继承自contract合约。test_da( account_name self ):contract(self){}是test_da合约的构造函数。
  2. 下面是对create函数的声明。
  3. 接下来是对数据字段的定义。这里我们定义了数据结构da.
  4. primary_key函数是定义主键的函数。　
  5. 接下来我们定义了辅助主键返回poster。
  6. EOSLIB_SERIALIZE宏的第一个参数是数据结构，其他参数是数据结构中的数据成员。
  7. typedef我们在这里定义了一个名字为das的类型，它用来定义数据库对象。这里我们定义的是一个具有主键及一个辅助键的数据库对象。

ABI文件 abi 非常重要，错误的abi会导致合约执行失败。

  1. {
  2.   "types": [],
  3.   "structs": [{
  4.       "name": "da",
  5.       "base": "",
  6.       "fields": [{
  7.           "name": "post_id",
  8.           "type": "uint64"
  9.         },{
  10.           "name": "poster",
  11.           "type": "account_name"
  12.         },{
  13.           "name": "title",
  14.           "type": "string"
  15.         },{
  16.           "name": "content",
  17.           "type": "string"
  18.         }
  19.       ]
  20.     },{
  21.       "name": "create",
  22.       "base": "",
  23.       "fields": [{
  24.           "name": "user",
  25.           "type": "account_name"
  26.         },{
  27.           "name": "title",
  28.           "type": "string"
  29.         },{
  30.           "name": "content",
  31.           "type": "string"
  32.         }
  33.       ]
  34.     }}
  35.   ],
  36.   "actions": [{
  37.           "name": "create",
  38.           "type": "create",
  39.         }
  40.   ],
  41.   "tables": [{
  42.       "name": "data",
  43.       "index_type": "i64",
  44.       "key_names": [
  45.         "post_id"
  46.       ],
  47.       "key_types": [
  48.         "uint64"
  49.       ],
  50.       "type": "da"
  51.     }
  52.   ],
  53.   "ricardian_clauses": []
  54. }

接下来来演示一下:

  1. 发布合约

    1. cleos set contract eosio test_da     
    2. Reading WAST/WASM from test_da/test_da.wasm...
    3. Using already assembled WASM...
    4. Publishing contract...
    5. executed transaction: 3d6f04278617d3807fe876a33057f1155acf9c9e5a392ac6ed8ad51e79506009  6752 bytes  24679 us
    6. #         eosio <= eosio::setcode               {"account":"eosio","vmtype":0,"vmversion":0,"code":"0061736d0100000001ad011a60037f7e7e0060057f7e7e7f...
    7. #         eosio <= eosio::setabi                {"account":"eosio","abi":{"types":[],"structs":[{"name":"da","base":"","fields":[{"name":"post_id","...

  2. 创建数据

    1. cleos push action eosio create '{"user":"eosio","title":"first","content":"create a first one"}' -p eosio
    2. executed transaction: 830057f270fa499b1d61b82e80ad8cda1774cdc1786c1e786f558a3e0a48974c  216 bytes  17229 us
    3. #         eosio <= eosio::create                {"user":"eosio","title":"first","content":"create a first one"}

下面我们来查一下数据表：

  1. cleos get table eosio eosio data
  2. {
  3.   "rows": [{
  4.       "post_id": 0,
  5.       "poster": "eosio",
  6.       "title": "first",
  7.       "content": "create a first one"
  8.     }
  9.   ],
  10.   "more": false
  11. }

创建信息成功，那么我们用别的账号创建会怎样呢？

  1. cleos push action eosio create '{"user":"eostea","title":"eostea first","content":"eostea create a first one"}' -p eostea
  2. executed transaction: 8542a87e563a9c62b7dbe46ae09ccf829c7821f8879167066b658096718de148  232 bytes  2243 us
  3. #         eosio <= eosio::create                {"user":"eostea","title":"eostea first","content":"eostea create a first one"}

查看数据表：

  1. cleos get table eosio eostea data
  2. {
  3.   "rows": [{
  4.       "post_id": 0,
  5.       "poster": "eostea",
  6.       "title": "eostea first",
  7.       "content": "eostea create a first one"
  8.     }
  9.   ],
  10.   "more": false
  11. }

到这里，相信大家对创建数据已经没有什么疑惑了。

查询

对于数据库，最重要的功能就是查询，如果没有查询功能，数据库里的数据就不能呈现，也就没有意义。查询数据库主要分为两方面，一方面是主键查询，一方面是通过二级索引查询。

这里为了使表中数据多样化我会做一些修改，将所有数据都合到一张表中。 我将以上.cpp中的das datable( _self, user);改为das datable( _self, _self);.这样数

据都存在合约账户的表中。

主键查询

这里我添加了一个方法来查询数据并打印：

  1. void test_da::getd(uint64_t post_id){
  2.         das datable(_self, _self);
  3.         auto post_da = datable.find( post_id);
  4.         eosio::print("Post_id: ", post_da->post_id, "  Post_Tile: ", post_da->title.c_str(), " Content: ", post_da->content.c_str());
  5.     }

ABI文件也做了相应的调整，执行：

  1. cleos push action eosio getd '{"post_id":1}' -p eosio
  2. executed transaction: ac8663235462d947c74542af848cca54a059c3991d193237025da7d4767d6725  192 bytes  1724 us
  3. #         eosio <= eosio::getd                  {"post_id":1}
  4. >> Post_id: 1  Post_Tile: first Content: eosio create a first one

二级索引查询

添加二级索引查询代码如下：

  1. auto poster_index = datable.template get_index<N(byposter)>();
  2. auto pos = poster_index.find( user );
  4. for (; pos != poster_index.end(); pos++)
  5. {
  6.     eosio::print("content:", pos->content.c_str(), " post_id:", pos->post_id, " title:", pos->title.c_str());
  7. }

获取二级索引并获取数据，这里我只用了find查询，其他查询就不在一一介绍。

执行getd操作：

  1. cleos push action eosio getd '{"post_id":2,"user": "eostea"}' -p eosio
  2. executed transaction: 2370e1fb1ee8a581f7321f02fb40645e51269e579d183c33ef470dba0b3afdbc  200 bytes  5403 us
  3. #         eosio <= eosio::getd                  {"post_id":2,"user":"eostea"}
  4. >> Post_id: 2  Post_Tile: eostea first Content: eostea create a first onecontent:eostea create a first one post_id:2 title:eostea first

数据库中数据如下：

  1. cleos get table eosio eosio data
  2. {
  3.  "rows": [{
  4.      "post_id": 0,
  5.      "poster": "eosio",
  6.      "title": "first",
  7.      "content": "eostea create a first one"
  8.    },{
  9.      "post_id": 1,
  10.      "poster": "eosio",
  11.      "title": "first",
  12.      "content": "eostea create a first one"
  13.    },{
  14.      "post_id": 2,
  15.      "poster": "eostea",
  16.      "title": "eostea first",
  17.      "content": "eostea create a first one"
  18.    }
  19.  ],
  20.  "more": false
  21. }

更改

更改数据库内容。 这里我们先看一下目前的数据库内容。

  1. cleos get table eosio eosio data
  2. {
  3.  "rows": [{
  4.      "post_id": 0,
  5.      "poster": "eosio",
  6.      "title": "first",
  7.      "content": "eostea create a first one"
  8.    },{
  9.      "post_id": 1,
  10.      "poster": "eosio",
  11.      "title": "first",
  12.      "content": "eostea create a first one"
  13.    },{
  14.      "post_id": 2,
  15.      "poster": "eostea",
  16.      "title": "eostea first",
  17.      "content": "eostea create a first one"
  18.    }
  19.  ],
  20.  "more": false
  21. }

写一个更改数据的action代码如下：

  1. void test_da::change(account_name user, uint64_t post_id, string title, string content)
  2.     {
  3.         require_auth(user);
  4.         das datable( _self, user);
  5.         auto post = datable.find(post_id);
  6.         eosio_assert(post->poster == user, "yonghucuowu");
  7.         datable.modify(post, user, [&](auto& p){
  8.             if (title != "")
  9.                 p.title = title;
  10.             if (content != "")
  11.                 p.content = content;
  12.         });
  13.     }

前几行代码之前讲解过，现在直接说modify方法，他的第一个参数是你查询出的要更改的对象，第二个参数是payer,其他的不用多说。

下面我们执行一下命令：

  1. cleos push action eosio change '{"user":"eosio","post_id":1,"title":"change","content":"change action"}' -p eosio
  2. executed transaction: 8cb561a712f2741560118651aefd49efd161e3d73c56f6d24cf1d699c265e2dc  224 bytes  2130 us
  3. #         eosio <= eosio::change                {"user":"eosio","post_id":1,"title":"change","content":"change action"}

下面我们看一下数据库：

  1. cleos get table eosio eosio data
  2. {
  3.   "rows": [{
  4.       "post_id": 0,
  5.       "poster": "eosio",
  6.       "title": "first",
  7.       "content": "eostea create a first one"
  8.     },{
  9.       "post_id": 1,
  10.       "poster": "eosio",
  11.       "title": "change",
  12.       "content": "change action"
  13.     },{
  14.       "post_id": 2,
  15.       "poster": "eostea",
  16.       "title": "eostea first",
  17.       "content": "eostea create a first one"
  18.     }
  19.   ],
  20.   "more": false
  21. }

post_id=1的记录已经被改变，说明我们成功了。

删除数据

删除数据我又加了一个action,如下所示:

  1. void test_da::dele(account_name user, uint64_t post_id)
  2.     {
  3.         require_auth(user);
  4.         das datable( _self, user);
  5.         auto post = datable.find(post_id);
  6.         eosio::print(post->title.c_str());
  8.         eosio_assert(post->poster == user, "yonghucuowu");
  9.         datable.erase(post);
  10.     }

这里调用了erase方法删除数据，参数为一个数据对象。下面我们来看一下执行结果：

  1. cleos push action eosio dele '{"user":"eosio","post_id":1}' -p eosioexecuted transaction: 3affbbbbd1da328ddcf37753f1f2f6c5ecc36cd81a0e12fea0c789e75b59714e  200 bytes  2383 us
  2. #         eosio <= eosio::dele                  {"user":"eosio","post_id":1}

现在再来看一下我们的数据库：

  1. cleos get table eosio eosio data
  2. {
  3.   "rows": [{
  4.       "post_id": 0,
  5.       "poster": "eosio",
  6.       "title": "first",
  7.       "content": "eostea create a first one"
  8.     },{
  9.       "post_id": 2,
  10.       "poster": "eostea",
  11.       "title": "eostea first",
  12.       "content": "eostea create a first one"
  13.     }
  14.   ],
  15.   "more": false
  16. }

post_id=1的数据已经被我们删除。

到这里，数据库的增删改查已经讲解完毕，最终的智能合约：

.cpp

  1. #include "test_da/test_da.hpp"
  3. namespace eosio {
  5.     void test_da::create(account_name user, string title, string content)
  6.     {
  7.         require_auth( user );
  8.         das datable( _self, _self);
  9.         datable.emplace(user, [&]( da & d){
  10.             d.title = title;
  11.             d.content = content;
  12.             d.post_id = datable.available_primary_key();
  13.             d.poster = user;
  14.         });
  15.     }
  17.     void test_da::change(account_name user, uint64_t post_id, string title, string content)
  18.     {
  19.         require_auth(user);
  20.         das datable( _self, user);
  21.         auto post = datable.find(post_id);
  22.         eosio_assert(post->poster == user, "yonghucuowu");
  23.         datable.modify(post, user, [&](auto& p){
  24.             if (title != "")
  25.                 p.title = title;
  26.             if (content != "")
  27.                 p.content = content;
  28.         });
  29.     }
  31.     void test_da::dele(account_name user, uint64_t post_id)
  32.     {
  33.         require_auth(user);
  34.         das datable( _self, user);
  35.         auto post = datable.find(post_id);
  36.         eosio::print(post->title.c_str());
  38.         eosio_assert(post->poster == user, "yonghucuowu");
  39.         datable.erase(post);
  40.     }
  42.     void test_da::getd(uint64_t post_id, account_name user){
  43.         das datable(_self, _self);
  44.         auto post_da = datable.find( post_id);
  45.         eosio::print("Post_id: ", post_da->post_id, "  Post_Tile: ", post_da->title.c_str(), " Content: ", post_da->content.c_str());
  47.         auto poster_index = datable.template get_index<N(byposter)>();
  48.         auto pos = poster_index.find( user );
  50.         for (; pos != poster_index.end(); pos++)
  51.         {
  52.             eosio::print("content:", pos->content.c_str(), " post_id:", pos->post_id, " title:", pos->title.c_str());
  53.         }
  54.     }
  56. }
  57. EOSIO_ABI(eosio::test_da, (create)(change)(dele)(getd))

.hpp

  1. #include <eosiolib/eosio.hpp>
  2. #include <string>
  4. namespace eosio {
  5. using std::string;
  6. class test_da : public contract {
  7.      public:
  8.            test_da( account_name self ):contract(self){}
  10.            // @abi action
  11.            void create(account_name user, string title, string content);
  12.            void change(account_name user, uint64_t post_id, string title, string content);
  13.            void dele(account_name user, uint64_t post_id);
  14.            void getd(uint64_t post_id, account_name user);
  16.      private:
  17.            // @abi table data i64
  18.            struct da {
  19.                  uint64_t     post_id;
  20.                  account_name poster;
  21.                  string       title;
  22.                  string       content;
  24.                  uint64_t primary_key()const { return post_id; }
  25.                  account_name get_poster() const { return poster; }
  27.                  EOSLIB_SERIALIZE(da, (post_id)(poster)(title)(content))
  28.            };
  29.            typedef eosio::multi_index<N(data), da, indexed_by<N(byposter), const_mem_fun<da, account_name, &da::get_poster>> > das;
  30.   };
  31. } /// namespace eosio

.abi

  1. {
  2.   "types": [],
  3.   "structs": [{
  4.       "name": "da",
  5.       "base": "",
  6.       "fields": [{
  7.           "name": "post_id",
  8.           "type": "uint64"
  9.         },{
  10.           "name": "poster",
  11.           "type": "account_name"
  12.         },{
  13.           "name": "title",
  14.           "type": "string"
  15.         },{
  16.           "name": "content",
  17.           "type": "string"
  18.         }
  19.       ]
  20.     },{
  21.       "name": "create",
  22.       "base": "",
  23.       "fields": [{
  24.           "name": "user",
  25.           "type": "account_name"
  26.         },{
  27.           "name": "title",
  28.           "type": "string"
  29.         },{
  30.           "name": "content",
  31.           "type": "string"
  32.         }
  33.       ]
  34.     },{
  35.       "name": "change",
  36.       "base": "",
  37.       "fields": [{
  38.           "name": "user",
  39.           "type": "account_name"
  40.         },{
  41.           "name": "post_id",
  42.           "type": "uint64"
  43.         },{
  44.           "name": "title",
  45.           "type": "string"
  46.         },{
  47.           "name": "content",
  48.           "type": "string"
  49.         }
  50.       ]
  51.     },{
  52.       "name": "dele",
  53.       "base": "",
  54.       "fields": [{
  55.           "name": "user",
  56.           "type": "account_name"
  57.         },{
  58.           "name": "post_id",
  59.           "type": "uint64"
  60.         }
  61.       ]
  62.     },{
  63.       "name": "get_data",
  64.       "base": "",
  65.       "fields": [{
  66.           "name": "post_id",
  67.           "type": "uint64"
  68.         },{
  69.           "name": "user",
  70.           "type": "account_name"
  71.         }
  72.       ]
  73.     }
  74.   ],
  75.   "actions": [{
  76.           "name": "create",
  77.           "type": "create",
  78.         },{
  79.           "name": "change",
  80.           "type": "change",
  81.         },{
  82.           "name": "dele",
  83.           "type": "dele",
  84.         },{
  85.           "name": "getd",
  86.           "type": "get_data",
  87.         }
  88.   ],
  89.   "tables": [{
  90.       "name": "data",
  91.       "index_type": "i64",
  92.       "key_names": [
  93.         "post_id"
  94.       ],
  95.       "key_types": [
  96.         "uint64"
  97.       ],
  98.       "type": "da"
  99.     }
  100.   ],
  101.   "ricardian_clauses": []
  102. }