Views

The View class in Weasel.Firebird.Views manages a Firebird view: the SELECT after AS, created, compared and dropped like any other schema object.

Defining a View

var view = new View("active_users",
    "SELECT id, name, email FROM users WHERE is_active");

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A name without a schema lives in PUBLIC; any other schema is refused. See No schemas before Firebird 6.

Generating DDL

var migrator = new FirebirdMigrator();
var writer = new StringWriter();

view.WriteCreateStatement(migrator, writer);
// CREATE OR ALTER VIEW active_users AS SELECT id, name, email FROM users WHERE is_active;

view.WriteDropStatement(migrator, writer);
// An EXECUTE BLOCK that drops the view only while it exists

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Statement	Written as
Create	CREATE OR ALTER VIEW name AS query, one plain statement
Update	The same statement: the view is altered in place, never dropped first
Drop	An EXECUTE BLOCK that runs DROP VIEW only while the view exists
Racing appliers	A CREATE OR ALTER that loses a catalog race runs again, so every applier succeeds

CREATE OR ALTER VIEW adds, removes, renames and retypes the view's columns. The views, procedures and triggers that use it, and the privileges granted on it, survive the change. Firebird refuses one change: removing a column that something else still uses. Dropping the view first would be refused for the same reason.

A trailing ; in the query is left off.

Delta Detection

await using var conn = new FbConnection(connectionString);
await conn.OpenAsync();

var delta = await view.FindDeltaAsync(conn);
// Create, Update or None

await view.ApplyChangesAsync(conn);

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Firebird keeps the query as it was written, in RDB$RELATIONS.RDB$VIEW_SOURCE, so the two texts are compared:

Difference	Change?
Whitespace, line breaks	No
Case outside literals	No
A trailing ;	No
A literal ('one' vs 'ONE')	Yes
A comment	Yes: it is part of the stored text

The source is read whole, however long the query. A view named like an existing table reports Create, and Firebird refuses the CREATE OR ALTER VIEW rather than replacing the table.

Teardown

DropSchemaAsync drops every view, a view over a view included.