Document database BLOB storage provider

docs/en/framework/infrastructure/blob-storing/database.md

@@ -9,6 +9,8 @@
 
 BLOB Storing Database Storage Provider can store BLOBs in a relational or non-relational database.
 
+The database provider reads the complete input stream into memory before saving a BLOB and returns BLOB content from an in-memory buffer. Database and driver value-size limits still apply. Consider an external object-storage provider for very large BLOBs or workloads that require end-to-end streaming.
+
 There are two database providers implemented;
 
 * [Volo.Abp.BlobStoring.Database.EntityFrameworkCore](https://www.nuget.org/packages/Volo.Abp.BlobStoring.Database.EntityFrameworkCore) package implements for [EF Core](../../data/entity-framework-core), so it can store BLOBs in [any DBMS supported](https://docs.microsoft.com/en-us/ef/core/providers/) by the EF Core.
@@ -32,16 +34,16 @@ This command adds all the NuGet packages to corresponding layers of your solutio
 
 ### Manual Installation
 
-Here, all the NuGet packages defined by this provider;
+The following NuGet packages are defined by this provider:
 
 * [Volo.Abp.BlobStoring.Database.Domain.Shared](https://www.nuget.org/packages/Volo.Abp.BlobStoring.Database.Domain.Shared)
 * [Volo.Abp.BlobStoring.Database.Domain](https://www.nuget.org/packages/Volo.Abp.BlobStoring.Database.Domain)
 * [Volo.Abp.BlobStoring.Database.EntityFrameworkCore](https://www.nuget.org/packages/Volo.Abp.BlobStoring.Database.EntityFrameworkCore)
 * [Volo.Abp.BlobStoring.Database.MongoDB](https://www.nuget.org/packages/Volo.Abp.BlobStoring.Database.MongoDB)
 
-You can only install Volo.Abp.BlobStoring.Database.EntityFrameworkCore or Volo.Abp.BlobStoring.Database.MongoDB (based on your preference) since they depends on the other packages.
+You only need to install Volo.Abp.BlobStoring.Database.EntityFrameworkCore or Volo.Abp.BlobStoring.Database.MongoDB (based on your preference), since they depend on the other packages.
 
-After installation, add `DepenedsOn` attribute to your related [module](../../architecture/modularity/basics.md). Here, the list of module classes defined by the related NuGet packages listed above:
+After installation, add the `[DependsOn]` attribute to your related [module](../../architecture/modularity/basics.md). Here is the list of module classes defined by the related NuGet packages listed above:
 
 * `BlobStoringDatabaseDomainModule`
 * `BlobStoringDatabaseDomainSharedModule`
@@ -52,6 +54,17 @@ Whenever you add a NuGet package to a project, also add the module class depende
 
 If you are using EF Core, you also need to configure your **Migration DbContext** to add BLOB storage tables to your database schema. Call `builder.ConfigureBlobStoring()` extension method inside the `OnModelCreating` method to include mappings to your DbContext. Then you can use the standard `Add-Migration` and `Update-Database` [commands](https://docs.microsoft.com/en-us/ef/core/managing-schemas/migrations/) to create necessary tables in your database.
 
+If you are using MongoDB and combine module collections in a custom `AbpMongoDbContext`, call `modelBuilder.ConfigureBlobStoring()` inside the `CreateModel` method:
+
+````csharp
+protected override void CreateModel(IMongoModelBuilder modelBuilder)
+{
+    base.CreateModel(modelBuilder);
+
+    modelBuilder.ConfigureBlobStoring();
+}
+````
+
 ## Configuration
 
 ### Connection String
@@ -60,9 +73,17 @@ If you will use your `Default` connection string, you don't need to any addition
 
 If you want to use a separate database for BLOB storage, use the `AbpBlobStoring` as the [connection string](../../fundamentals/connection-strings.md) name in your configuration file (`appsettings.json`). In this case, also read the [EF Core Migrations](../../data/entity-framework-core/migrations.md) document to learn how to create and use a different database for a desired module.
 
+### Common Database Properties
+
+The `AbpBlobStoringDatabaseDbProperties` class defines the following database settings. Set `DbTablePrefix` and `DbSchema` at application startup, before the database model is created:
+
+* `DbTablePrefix` (`Abp` by default) is the prefix for table and collection names.
+* `DbSchema` (`null` by default) is the database schema used by EF Core. MongoDB does not use this property.
+* `ConnectionStringName` (`AbpBlobStoring`) is the connection-string name used by both database providers.
+
 ### Configuring the Containers
 
-If you are using only the database storage provider, you don't need to manually configure it, since it is automatically done. If you are using multiple storage providers, you may want to configure it.
+The database module selects `DatabaseBlobProvider` for the default container when no provider has already been selected. It does not replace an explicitly configured provider. If you use multiple storage providers, configure the database provider for the required default, typed or named containers.
 
 Configuration is done in the `ConfigureServices` method of your [module](../../architecture/modularity/basics.md) class, as explained in the [BLOB Storing document](../blob-storing).
 
@@ -84,12 +105,18 @@ Configure<AbpBlobStoringOptions>(options =>
 
 It is expected to use the [BLOB Storing services](../blob-storing) to use the BLOB storing system. However, if you want to work on the database tables/entities, you can use the following information.
 
+### Database Tables and Collections
+
+With the default `Abp` prefix, EF Core maps the entities to the `AbpBlobContainers` and `AbpBlobs` tables. MongoDB uses collections with the same names. Changing `DbTablePrefix` changes both table and collection names, while `DbSchema` only changes the EF Core schema.
+
 ### Entities
 
 Entities defined for this module:
 
-* `DatabaseBlobContainer` (aggregate root) represents a container stored in the database.
+* `DatabaseBlobContainer` (aggregate root) represents a container stored in the database. It stores the tenant identifier and the container name. Persisted container names have a maximum length of 128 characters.
-* `DatabaseBlob` (aggregate root) represents a BLOB in the database.
+* `DatabaseBlob` (aggregate root) represents a BLOB in the database. It stores the container identifier, tenant identifier, BLOB name and content. Persisted BLOB names have a maximum length of 256 characters.
+
+The provider creates a container record lazily when the first BLOB is saved to that container. Read, existence-check and delete operations do not create container records, and deleting the last BLOB does not delete its container record.
 
 See the [entities document](../../architecture/domain-driven-design/entities.md) to learn what is an entity and aggregate root.
 
@@ -102,4 +129,4 @@ You can also use `IRepository<DatabaseBlobContainer, Guid>` and `IRepository<Dat
 
 ### Other Services
 
-* `DatabaseBlobProvider` is the main service that implements the database BLOB storage provider, if you want to override/replace it via [dependency injection](../../fundamentals/dependency-injection.md) (don't replace `IBlobProvider` interface, but replace `DatabaseBlobProvider` class).
+* `DatabaseBlobProvider` is the main service that implements the database BLOB storage provider, if you want to override/replace it via [dependency injection](../../fundamentals/dependency-injection.md) (don't replace `IBlobProvider` interface, but replace `DatabaseBlobProvider` class).