Method executeSelectQuery

server/conn_query_exec.go:153–319

executeSelectQuery runs a result-returning query against DuckDB and streams results to the client. Sends RowDescription, DataRow messages, CommandComplete, and ReadyForQuery. Returns the number of rows sent, any SQLSTATE+message sent to the client, and any connection-level error.

(query string, cmdType string)

		rewritten += ";"
	}
	return rewritten
}

// namesDuckLakeCatalog reports whether name is this session's logical alias for
// the physical DuckLake catalog. True only when the session actually executes
// against DuckLake and its PG-visible database name differs from the physical
// one — i.e. the control plane accepted an org catalog name at connect. Every
// other session (standalone, plain "ducklake", memory) has no alias, so this is
// false and nothing new is rewritten.
//
// The empty-database guard is load-bearing, not belt-and-braces. `USE ""`
// arrives here as an empty name — rewriteDirectQuery's empty-target check runs
// BEFORE quote-stripping, so `""` passes it and unquotes to "". Without the
// guard, a session whose database is unset matches its own empty name and
// invalid SQL is silently rewritten into `USE ducklake.main`.
//
// TODO: a catalog-qualified `SET search_path = '<alias>.main'` is NOT rewritten
// and fails on the worker, while the physical `'ducklake.main'` works. Neither
// this function nor the transpiler's LogicalCatalogTransform sees it: the
// catalog name sits inside a string literal, not a RangeVar, so the AST pass
// has nothing to match on and this pass only inspects `USE`. Left alone
// deliberately — SQLMesh selects a catalog with `USE <catalog>` as its own
// statement (the path above), and uses search_path only in dbt code it marks
// unsupported. Fix it here if a client ever needs the qualified form.
func (c *clientConn) namesDuckLakeCatalog(name string) bool {
	return c.physicalCatalog == physicalDuckLakeCatalog &&
		c.database != "" &&
		!strings.EqualFold(c.database, physicalDuckLakeCatalog) &&
		strings.EqualFold(c.database, name)
}

// physicalDuckLakeCatalog is the physical catalog name DuckLake is attached as.
const physicalDuckLakeCatalog = "ducklake"

// executeSelectQuery runs a result-returning query against DuckDB and streams results to the client.
// Sends RowDescription, DataRow messages, CommandComplete, and ReadyForQuery.
// Returns the number of rows sent, any SQLSTATE+message sent to the client,
// and any connection-level error.
func (c *clientConn) executeSelectQuery(query string, cmdType string, workerStatements ...workerStatement) (int64, string, string, error) {
	ctx, cleanup := c.queryContext()
	defer cleanup()
	statement := workerStatementWithQuery(workerOriginClient, workerOperationSelect, query)
	if len(workerStatements) > 0 {
		statement = workerStatements[0]
	}

	execStart := time.Now()
	execCtx, execSpan := observe.Tracer().Start(ctx, "duckgres.execute")
	var queryRowsAff int64
	var queryFinalErr error
	c.logWorkerStatementStarted(statement)
	defer func() {
		c.logWorkerStatementFinished(statement, execStart, queryRowsAff, queryFinalErr)
	}()
	runQuery := func() (RowSet, error) {
		return c.executor.QueryContext(ctx, query)
	}