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73 lines
2.8 KiB
Plaintext
73 lines
2.8 KiB
Plaintext
/**
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* This class allows to include a set of layers in a database-side transaction,
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* provided the layer data providers support transactions and are compatible
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* with each other.
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*
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* Only layers which are not in edit mode can be included in a transaction,
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* and all layers need to be in read-only mode for a transaction to be committed
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* or rolled back.
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*
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* Layers cannot only be included in one transaction at a time.
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*
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* When editing layers which are part of a transaction group, all changes are
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* sent directly to the data provider (bypassing the undo/redo stack), and the
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* changes can either be committed or rolled back on the database side via the
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* QgsTransaction::commit and QgsTransaction::rollback methods.
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*
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* As long as the transaction is active, the state of all layer features reflects
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* the current state in the transaction.
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*
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* Edits on features can get rejected if another conflicting transaction is active.
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*/
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class QgsTransaction : QObject /Abstract/
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{
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%TypeHeaderCode
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#include <qgstransaction.h>
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%End
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public:
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/** Creates a transaction for the specified connection string and provider */
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static QgsTransaction *create( const QString &connString, const QString &providerKey ) /Factory/;
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/** Creates a transaction which includes the specified layers. Connection string
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* and data provider are taken from the first layer */
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static QgsTransaction *create( const QStringList &layerIds ) /Factory/;
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virtual ~QgsTransaction();
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/** Add layer to the transaction. The layer must not be in edit mode.*/
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bool addLayer( const QString &layerId );
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/** Add layer to the transaction. The layer must not be in edit mode.*/
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bool addLayer( QgsVectorLayer *layer );
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/** Begin transaction
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* The statement timeout, in seconds, specifies how long an sql statement
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* is allowed to block QGIS before it is aborted. Statements can block,
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* depending on the provider, if multiple transactions are active and a
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* statement would produce a conflicting state. In these cases, the
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* statements block until the conflicting transaction is committed or
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* rolled back.
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* Some providers might not honour the statement timeout. */
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bool begin( QString &errorMsg /Out/, int statementTimeout = 20 );
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/** Commit transaction. All layers need to be in read-only mode. */
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bool commit( QString &errorMsg /Out/ );
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/** Roll back transaction. All layers need to be in read-only mode. */
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bool rollback( QString &errorMsg /Out/ );
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/** Executes sql */
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virtual bool executeSql( const QString &sql, QString &error /Out/ ) = 0;
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/**
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* Checks if a the provider of a give layer supports transactions.
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*/
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static bool supportsTransaction( const QgsVectorLayer *layer );
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signals:
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/**
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* Emitted after a rollback
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*/
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void afterRollback();
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};
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