PCLT-DB-0.1.1: An addon to PCLT package: enchance PCLT catalog with PostgreSQL powers.

Database.PCLT.InterfaceWithDB

Contents

Description

Some instances of ReadableFromDB for reading PCLT catalog and related objects from DB.

DBMS is PostgreSQL v8.4. Not earlier, since PCLT-DB relies on a feature that appeared in PostgresSQL only in v8.4. - the WITH clause for SELECT query (also WITH RECURSIVE).

Synopsis

Instances of ReadableFromDB

newtype RawCatalogDataReadFromDBResult Source

Container for data, that is read from DB, that goes on input to catalog formation routine.

Constructors

RawCatalogDataReadFromDBResult (PCLT_RawCatalogData, [AddPCLT_toPCLT_Error]) 

Instances

newtype CatalogReadFromDBResult Source

Container for PCLT catalog, that is read from DB.

Constructors

CatalogReadFromDBResult (PCLT_Catalog, [ErrorWithPCSCatalog ReadPCSCatalogError], [AddPCLT_toPCLT_Error]) 

Instances

newtype CatalogNeedsToBeUpdated_DoesIt Source

Container for a flag, that is read from DB.

For each catalog in DB there is stored a special flag "catalog data or config changed". The flag gets raised by an army of triggers, that watches every table, and is thought to get dropped by a program, which uses DB catalog. Drop the flag right before catalog update from DB.

Unfortunately, the current implementation of this flagging system constraints the number of agents that update their catalogs from DB by only one (because, when agent updates it's catalog, it drops the flag, and other agents don't know that flag was risen, so they can't know if version of catalog in their operative memory is older then in DB or is it not).

But this limitation removal is planned as a first ToDo in the next version of PCLT-DB.

Constructors

CatalogNeedsToBeUpdated_DoesIt Bool 

Instances

Drop flag "catalog data or config changed" in DB

data DropFlag_CatalogNeedsToBeUpdated_Error Source

Errors that may occur, when performing dropFlag_CatalogNeedsToBeUpdated.

Constructors

NotModified_DFCNTBUE 
DBError_DFCNTBUE SqlError 

Instances

data AddressedDropFlag_CatalogNeedsToBeUpdated_Error Source

Wrapper around DropFlag_CatalogNeedsToBeUpdated_Error, added PCLT_CatalogID, for which "drop flag" operation failed.

Constructors

AddressedDropFlag_CatalogNeedsToBeUpdated_Error DropFlag_CatalogNeedsToBeUpdated_Error PCLT_CatalogID 

Instances

dropFlag_CatalogNeedsToBeUpdated :: Connection -> PCLT_CatalogID -> IO (Maybe AddressedDropFlag_CatalogNeedsToBeUpdated_Error)Source

Drop that flag in DB.

Consider catalog update

data CatalogUpdateFromDBErrors Source

The container for all types of errors that may result, when trying to update a catalog from DB.

Constructors

CatalogUpdateFromDBErrors 

Fields

cueDropCNTBUFlag :: Maybe AddressedDropFlag_CatalogNeedsToBeUpdated_Error
 
cueARFDBE :: Maybe AddressedReadFromDBError
 
cueCatReadErrs :: [ErrorWithPCSCatalog ReadPCSCatalogError]
 
cueCollectionErrs :: [AddPCLT_toPCLT_Error]
 
cueCatalogID :: PCLT_CatalogID
 
cueCatalogRead :: Bool
 

Instances

emptyCUE :: CatalogUpdateFromDBErrors -> BoolSource

Checks if catalog is read without a single error.

defaultCatalogUpdateFromDBErrors :: PCLT_CatalogID -> CatalogUpdateFromDBErrorsSource

An empty form to be filled.

cfhie2cue :: CatalogFromHSRTInitErrors -> CatalogUpdateFromDBErrorsSource

There is a one way relation from CatalogFromHSRTInitErrors to CatalogUpdateFromDBErrors. That's because subject operations are similar it their abstractions.

considerCatalogUpdate :: Connection -> PCLT_CatalogID -> IO (Maybe PCLT_Catalog, Maybe CatalogUpdateFromDBErrors)Source

Check if the flag "catalog data or config changed" is up in DB. If so, drop it and try to read from DB

  1. PCLT_InnerConfig
  2. RawCatalogDataReadFromDBResult
  3. CatalogReadFromDBResult