我有一个 Ruby 程序，它使用 DataMapper 作为 ORM 来与内存中的 SQLite 数据库对话。这一直工作正常，但我最近刚刚添加了一个新的 DM 类和相应的表。令我惊讶的是，事情现在在 auto_migrate 期间爆炸了!

这是 DataMapper 生成的 SQL:

~ (0.000390) PRAGMA table_info("sensationd_channels")
~ (0.000010) PRAGMA table_info("sensationd_commands")
~ (0.000009) PRAGMA table_info("sensationd_configurations")
~ (0.000052) PRAGMA table_info("sensationd_measurements")
~ (0.000028) SELECT sqlite_version(*)
~ (0.000035) DROP TABLE IF EXISTS "sensationd_channels"
~ (0.000009) PRAGMA table_info("sensationd_channels")
~ (0.000423) CREATE TABLE "sensationd_channels" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "channel" INTEGER NOT NULL, "name" VARCHAR(50), "precision" INTEGER DEFAULT 11, "gain" INTEGER DEFAULT 1, "differential" BOOLEAN DEFAULT 'f', "configuration_id" INTEGER NOT NULL)
~ (0.000191) CREATE INDEX "index_sensationd_channels_configuration" ON "sensationd_channels" ("configuration_id")
~ (0.000015) DROP TABLE IF EXISTS "sensationd_commands"
~ (0.000009) PRAGMA table_info("sensationd_commands")
~ (0.000153) CREATE TABLE "sensationd_commands" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "action" INTEGER DEFAULT 1, "complete" BOOLEAN DEFAULT 'f', "issued_at" TIMESTAMP, "completed_at" TIMESTAMP)
~ (0.000015) DROP TABLE IF EXISTS "sensationd_configurations"
~ (0.000009) PRAGMA table_info("sensationd_configurations")
~ (0.000155) CREATE TABLE "sensationd_configurations" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "created_on" TIMESTAMP, "modified_on" TIMESTAMP, "name" VARCHAR(50) NOT NULL, "active" BOOLEAN)
~ (0.000015) DROP TABLE IF EXISTS "sensationd_measurements"
~ (0.000009) PRAGMA table_info("sensationd_measurements")
~ (0.000152) CREATE TABLE "sensationd_measurements" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "timestamp" TIMESTAMP, "measurement" VARCHAR(65535) NOT NULL, "channel_id" INTEGER NOT NULL, "channel_configuration_id" INTEGER NOT NULL)
~ (0.000175) CREATE INDEX "index_sensationd_measurements_channel" ON "sensationd_measurements" ("channel_id", "channel_configuration_id")
~ (0.000083) SELECT "id", "created_on", "modified_on", "name", "active" FROM "sensationd_configurations" WHERE "active" = 't' ORDER BY "id" LIMIT 1
~ (0.000073) INSERT INTO "sensationd_configurations" ("created_on", "modified_on", "name", "active") VALUES ('2011-08-01T12:36:18-07:00', '2011-08-01T12:36:18-07:00', 'Test U6-Pro Configuration, differential.', 't')
~ (0.000109) SELECT "id", "action", "complete", "issued_at", "completed_at" FROM "sensationd_commands" ORDER BY "issued_at" DESC LIMIT 1
~ (0.000086) INSERT INTO "sensationd_channels" ("channel", "name", "precision", "gain", "differential", "configuration_id") VALUES (0, '0', 11, 0, 't', 1)
~ no such table: sensationd_commands (code: 1, sql state: , query: SELECT "id", "action", "complete", "issued_at", "completed_at" FROM "sensationd_commands" ORDER BY "issued_at" DESC LIMIT 1, uri: sqlite3::memory:?scheme=sqlite&user=&password=&host=&port=&query=&fragment=&adapter=sqlite3&path=:memory:)

看起来它创建表格很顺利，但是几行之后就找不到了。我认为我错误配置了数据库连接，除了找到其他表并且工作正常。

正在运行的软件:

• Ruby 1.9.2p289 通过 RVM
• SQLite3 @3.7.7.1 通过 MacPorts
• DataMapper gem 1.1.0 版

有谁知道为什么会这样，我能做些什么？

最佳答案

我怀疑问题是由于 DataMapper(或更准确地说，DataObjects，DataMapper 使用的数据库驱动程序)自动执行的线程池。线程之间不共享数据库连接。这对于像 postgresql 或 mysql 甚至 sqlite3 作为“文件支持”数据库的东西来说很好(甚至是有益的)。对于 sqlite3 的内存存储，连接是数据库。因此，其他线程将因此而失败。此外，在一段时间不活动(~1 分钟？)后，线程将被清理，数据库也将消失。

如果是这样，我不确定是否有简单的解决方法。您可以修改 do_sqlite3 来避免这种情况。另一种基本上应该同样快的替代方法是在内存驱动器上使用文件支持的 sqlite3 数据库。

关于ruby - 通过 DataMapper 来自 SQLite 内存数据库的 No Such Table 错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/6904298/