Open and parse files lazily #204
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rubenv
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Jan 27, 2022
migrate.go
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| type Migration struct { | ||
| Id string | ||
| Up []string | ||
| Down []string | ||
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| type MigrationData struct { | ||
| Up []string | ||
| Down []string | ||
| DisableTransactionUp bool | ||
| DisableTransactionDown bool | ||
| } | ||
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| type migrationFile struct { | ||
| dir http.FileSystem | ||
| root string | ||
| baseName string | ||
| } | ||
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| type Migration struct { | ||
| Id string | ||
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| // data may be nil if not parsed yet. | ||
| data *MigrationData | ||
| // file is information of migration file, which is used to parse later. | ||
| // file may be nil if migration file has already been parsed when Migration is initialized. | ||
| file *migrationFile | ||
| } |
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This is a problem really. It changes the external API of the library, which means it may break peoples code. And I'd rather not do that.
Unless we find a way to do this without breaking the API, I'm afraid this won't be an option.
This reverts commit 859f73b.
…le to be loaded only when needed.
KeiichiHirobe
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Current implementation always parse all of sql files, so may require a lot of time and memory if there are too many files or too big files in directory. But, in most of cases, we only need to parse 1~3 files because sort
byIddoes not need content of files, it needs only the name of files.So, I think it is better to parse sql files only when we need content of files.
Some migration sources are not supported to open/parse lazily in this PR.
HttpFileSystemMigrationSource,FileMigrationSourceandEmbedFileSystemMigrationSourceare supported,MemoryMigrationSource,AssetMigrationSourceandPackrBoxare not supported.I don't think that's a problem because I guess most users don't use the latter migration sources.
I believe lazy loading should be the default behavior, but I made it optional with
SetLazyLoad(true)to keep backward compatibility.ref: #203