c - Berkeley DB 的 db_stat 无法正常工作

Question

我从 Oracle 下载了 Berkeley DB 5.3.28 和 18.1.40，在 Ubuntu 18.04 上编译成功。一切都按预期工作，除了 db_stat 实用程序不想为我返回正确的数据库统计信息。特别是，没有唯一键，没有数据项等......都是错误的。

这是我的测试代码:

#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <db.h>


int main() {
  DB *dbp;
  DBT key, data;
  int ret, t_ret;

  ret = db_create(&dbp, NULL, 0);
    assert(ret == 0);

  ret = dbp->open(dbp, NULL, "sample.db", "", DB_BTREE, DB_CREATE, 0664);
  assert(ret == 0);

  memset(&key, 0, sizeof(key));
  memset(&data, 0, sizeof(data));
  key.data = (char*)"fruit";
  key.size = sizeof("fruit");
  data.data = (char*)"apple";
  data.size = sizeof("apple");

  ret = dbp->put(dbp, NULL, &key, &data, 0);
  assert(ret == 0);

  key.data = (char*)"color";
  key.size = sizeof("color");
  data.data = (char*)"red";
  data.size = sizeof("red");

  ret = dbp->put(dbp, NULL, &key, &data, 0);
  assert(ret == 0);

  key.data = (char*)"language";
  key.size = sizeof("language");
  data.data = (char*)"c";
  data.size = sizeof("c");

  ret = dbp->put(dbp, NULL, &key, &data, 0);
  assert(ret == 0);

  dbp->close(dbp, 0);
}

db_stat 输出:

db_stat -d sample.db

Sun Jun  7 20:26:59 2020    Local time
53162   Btree magic number
9   Btree version number
Little-endian   Byte order
multiple-databases  Flags
2   Minimum keys per-page
4096    Underlying database page size
1007    Overflow key/data size
1   Number of levels in the tree
1   Number of unique keys in the tree
1   Number of data items in the tree
0   Number of tree internal pages
0   Number of bytes free in tree internal pages (0% ff)
1   Number of tree leaf pages
4054    Number of bytes free in tree leaf pages (1% ff)
0   Number of tree duplicate pages
0   Number of bytes free in tree duplicate pages (0% ff)
0   Number of tree overflow pages
0   Number of bytes free in tree overflow pages (0% ff)
0   Number of empty pages
0   Number of pages on the free list

Answer 1

您在 dbp->open 调用中将数据库命名为 ""。因此，您还必须使用 -s 标志将其传递给 db_stat:

$ db_stat -d sample.db -s ""
Wed Jun 10 03:16:43 2020    Local time
53162   Btree magic number
9   Btree version number
Little-endian   Byte order
record-numbers, multiple-databases  Flags
2   Minimum keys per-page
8192    Underlying database page size
2031    Overflow key/data size
1   Number of levels in the tree
3   Number of unique keys in the tree
3   Number of data items in the tree
0   Number of tree internal pages
0   Number of bytes free in tree internal pages (0% ff)
1   Number of tree leaf pages
8090    Number of bytes free in tree leaf pages (1% ff)
0   Number of tree duplicate pages
0   Number of bytes free in tree duplicate pages (0% ff)
0   Number of tree overflow pages
0   Number of bytes free in tree overflow pages (0% ff)
0   Number of empty pages
0   Number of pages on the free list

(我的 BDB 默认为 8K 页面，但其他方面相同。)