PostgreSQL Metadata

浏览数：21 / 时间：2015年06月12日
 
In this overload first parameter is name of a collection, and second parameter is the array of restrictions to be applied when querying information. These restrictions specify which subset of the collection will be returned. The restrictions can include, for example, the database name (in this case, only collection elements belonging to this database will be returned) or the mask for the name of collection elements (only the elements satisfying this mask will be returned). The quantity and description of restrictions allowed for each metadata collection are represented in the table here. Their number can also be obtained from the return of the GetSchema() method. If the second parameter is null/Nothing, it is ignored.
Instead of specifying the metadata collection name as a string constant, you may use members of System.Data.DbMetaDataCollectionNames and Devart.Data.PostgreSql.PgSqlMetadataCollectionNames as the first GetSchema argument values. The members of these classes are the string fields, each field stores the corresponding metadata collection name. It is recommended to use these fields rather than manually input the collection names manually as the string constants because in case of using these fields, you will find misspellings at compile-time, and intellisense will show you all the available metadata collection names.
GetSchema Method Reference
GetSchema supports two kinds of wildcards: "%" and "_". These special characters behave exactly as in LIKE operator. "%" means zero or more of any characters, "_" means any single character.
When calling the GetSchema method, you can pass all or few of restrictions, applicable to the chosen collection. In the latter case, you have to put "%" wildcard in the place of omitted restriction, if it must be specified before the restriction you want to apply. For example, GetSchema("Casts", new string[] { "%", "%", "date" }) returns list of all casts to type "date". Or, suppose you want to query all functions within a certain schema: GetSchema("Functions", new string[] { "%", "public" }) returns list of all functions in schema public. Note that this collection may accept 8 restrictions, however, you do not need to specify all of them.
The following table provides detailed information on metadata collections that can be retrieved using the GetSchema method, and restrictions that can be applied for them. Some collections may be not supported in older server versions. If you try to get metadata for unsupported collection you will get exception with message "Collection not defined".

 

Collection Name
Number of restrictions
Remarks
MetaDataCollections 0
Returns this list. Same as using GetSchema() method without parameters.
ReservedWords 0
Lists all reserved words used in the server.
AggregateFunctions 2
GetSchema("AggregateFunctions") returns detailed list of all aggregate functions on the server.
  • The first restriction for this collection is a name of a function. If specified, the method returns all overloads with given name.
  • The second restriction is name of function definer. For example, you can issue "%" as the first restriction, and "postgres" as the second one, to obtain list of functions defined by user "postgres".

     
Arguments 5
GetSchema("AggregateFunctions") returns the list of the function arguments. The following restrictions may be specified:
  • Schema name
  • Function name
  • User name
  • Type
  • Function OID (for overload functions)
Casts 3
GetSchema("Casts") returns list of casts available on the server.
  • The first restriction for this collection is namespace of a cast.
  • The second restriction is source type for the cast.
  • The third restriction is target type for the cast.

     
Columns 3
Returns list of columns, their schema, table, type, and some extra information.
  • Restricted by schema name, GetSchema returns columns of all tables within the schema.
  • The second restriction is name of a table that GetSchema method should search in.
  • At last, you can set column name pattern to filter columns by name.

     
Databases 3
Returns list of databases on the server.
  • The first restriction is a name of a database.
  • The second restriction is definer‘s name.
  • The last restriction is encoding of the database.

     
DatasourceInformation 1
Returns information about data sources.
The only restriction is schema name.
Domains 9
Returns list of domains on the server. The restrictions for this collection are the following:
  • Domain name
  • Definer
  • OID type
  • Base type
  • Type length
  • Typmod
  • Number of dimensions
  • Schema name
  • OID

     
ForeignKeys 4
Returns list of foreign keys on the server. The restrictions for this collection are the following:
  • Key name
  • Schema name
  • Table name
  • OID

     
Functions 8
Returns list of functions on the server. The following restrictions may be specified:
  • Function name
  • Schema name
  • Definer
  • Language
  • Arguments count
  • Return type OID
  • Return type
  • OID

     
Groups 1
Lists all groups on the server, including IDs and members.
The only restriction is a group name.
Indexes 4
Returns list of indexes and their details. Restricted by:
  • Index name
  • Schema name
  • Table name
  • OID

     
Languages 2
Lists all languages on the server.
The first restriction is a language name, the second is OID.
NestedTables 5
Lists nested tables on the server. Restricted by:
  • Table name
  • Schema name
  • Parent table name
  • Parent schema name
  • OID

     
Operators 2
Returns list of operators allowed on the server.
Restrict it by OID and name.
PrimaryKeys 3
Returns list of primary keys on the server.
  • First restriction is key name.
  • Second is schema name
  • Third is table name

     
Schemas 2
Returns list of schemas on the server.
  • The first restriction is OID
  • The second restriction is schema name

     
Tables 4
Returns list of tables on the server. Restrict the collection with:
  • OID
  • Table name
  • Schema name
  • Definer

     
Triggers 6
Returns list of triggers on the server. Restricted by:
  • OID
  • Trigger name
  • Schema name
  • Definer
  • Language
  • Arguments count

     
Types 5
Returns list of types on the server. Restricted by:
  • OID
  • Type name
  • Schema name
  • Definer
  • Type Length

     
Users 1
Lists all users on the server.
When restricted by username, returns information about specific user.
Views 4
Returns list of types on the server. Restricted by:
  • OID
  • View name
  • Schema name
  • Definer

     

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