SQL-004 Test connection¶

UnitOfWork.TestConnection<TEntity>() proves database connectivity, session-factory build success, and the mapped table's existence/accessibility by running a bounded, always-empty LINQ query against a consumer-supplied entity type inside its own transaction. No rows are ever returned; only success or a thrown exception matters.

Classification¶

Field	Value
SQL ID	SQL-004
Operation type	Read
Execution method	ORM (NHibernate LINQ)
Database	Oracle / SQL Server / PostgreSQL (engine-neutral — identifier quoting and dialect vary by `options.Database`)
Schema	Unresolved** — `TEntity` is a generic type parameter; the table/schema come from the consumer's `ClassMap<TEntity>`
Command type	N/A (ORM-generated)
Business object	`UnitOfWork`
Criteria property	N/A — ORM
Lifecycle method	`UnitOfWork.TestConnection<TEntity>()`

Parameters¶

This statement has no parameters. The Where(x => false) predicate is a literal constant expression, so NHibernate's LINQ provider generates no bind variable for it.

Tables¶

Table	Role
TEntity	Source — unresolved, consumer-supplied generic entity; every column loaded by the consumer's `ClassMap<TEntity>`.

LINQ statement¶

Source: src/SAIF.NetCore.Nhibernate/SAIF.NetCore.NHibernate/SAIF.NetCore.NHibernate/UnitOfWork.cs:24. The queryable is obtained one line earlier via Repository<TEntity>.Query() (src/SAIF.NetCore.Nhibernate/SAIF.NetCore.NHibernate/SAIF.NetCore.NHibernate/Repository.cs:41-44).

// src/SAIF.NetCore.Nhibernate/SAIF.NetCore.NHibernate/SAIF.NetCore.NHibernate/Repository.cs:41-44
public IQueryable<TEntity> Query()
{
    return Session.Query<TEntity>();
}

// src/SAIF.NetCore.Nhibernate/SAIF.NetCore.NHibernate/SAIF.NetCore.NHibernate/UnitOfWork.cs:21-26
public void TestConnection<TEntity>()
{
    this.Begin();
    this.GetRepository<TEntity>().Query().Where(x => false).ToList();
    this.Commit();
}

Sample SQL¶

Inferred SQL: This SQL was inferred from the LINQ statement above and the NHibernate mappings. It is not concrete SQL from source code; NHibernate generates the executed statement at runtime, so aliases, column order, join syntax, and bind-parameter names may differ.

-- Inferred from LINQ (NHibernate mapping translation); not concrete SQL
SELECT
  T.*  -- unresolved mapping: TEntity (every column of the consumer's ClassMap<TEntity>)
FROM
  TEntity T  -- unresolved mapping: TEntity (table from the consumer's ClassMap<TEntity>)
WHERE
  1 = 0

Translation notes: - Unresolved mapping (by design): the library is generic over TEntity, so no table or column can be resolved from this repository. T.* stands for "every column the consumer mapping loads" (identity/composite-key, version, Map, References FK, and Component columns, in mapping order). No column name has been invented. - Illustration with the library's own test binding TestConnection<Dual>() (test project only, not shipped; DualMapping: Table("dual"), Id(x => x.Dummy).Column("Dummy")): the statement resolves to SELECT D.Dummy FROM dual D WHERE 1 = 0 on Oracle. - Constant predicate (version-dependent): NHibernate's LINQ provider renders the constant false lambda as an always-false predicate; the exact literal form (for example 1 = 0 or 0 = 1) depends on the resolved NHibernate version, which is not pinned.* - Materialization: ToList() is the materialization point. The result is discarded, and no operators run after it. - Engine-neutral: the statement shape is identical on Oracle, SQL Server, and PostgreSQL; only identifier quoting and dialect differ, chosen by options.Database. - Session strategy: the same SQL is issued under both stateful and stateless strategies (Query<T>() on ISession/IStatelessSession). Because the session is cleared first and holds no dirty entities, the stateful Commit() flush issues no DML.*

Operations and processes¶

Business rules¶

Note: Statements marked with * were inferred from code structure, naming conventions, or contextual evidence where direct confirmation was not available in source artifacts. Statements marked with ** could not be confirmed; treat as unknown until verified.

Sources¶

src/SAIF.NetCore.Nhibernate/SAIF.NetCore.NHibernate/SAIF.NetCore.NHibernate/UnitOfWork.cs
src/SAIF.NetCore.Nhibernate/SAIF.NetCore.NHibernate/SAIF.NetCore.NHibernate/Repository.cs