Function dsqlNullifyReturning

src/dsql/StmtNodes.cpp:10021–10064

Create a compound statement to initialize returning parameters.

// Create a compound statement to initialize returning parameters.
static StmtNode* dsqlNullifyReturning(DsqlCompilerScratch* dsqlScratch, StmtNode* input)
{
	if (dsqlScratch->isPsql())
		return input;

	auto& pool = dsqlScratch->getPool();
	ReturningClause* returning;

	if (auto eraseNode = nodeAs<EraseNode>(input))
		returning = eraseNode->dsqlReturning;
	else if (auto modifyNode = nodeAs<ModifyNode>(input))
		returning = modifyNode->dsqlReturning;
	else if (auto storeNode = nodeAs<StoreNode>(input))
		returning = storeNode->dsqlReturning;
	else
	{
		fb_assert(false);
		returning = nullptr;
	}

	if (!returning)
		return input;

	// If this is a RETURNING in DSQL, we need to initialize the output
	// parameters with NULL, to return in case of empty resultset in some
	// circumstances (for example WHERE CURRENT OF ... RETURNING).

	const auto nullAssign = FB_NEW_POOL(pool) CompoundStmtNode(pool);
	auto nullPtr = nullAssign->statements.getBuffer(returning->first->items.getCount());

	for (auto& retPtr : returning->second->items)
	{
		AssignmentNode* assign = FB_NEW_POOL(pool) AssignmentNode(pool);
		assign->asgnFrom = NullNode::instance();
		assign->asgnTo = retPtr;
		*nullPtr++ = assign;
	}

	// Return a compound statement with the initialization and the original statement.
	const auto list = FB_NEW_POOL(pool) CompoundStmtNode(pool);
	list->statements.add(nullAssign);
	list->statements.add(input);
	return list;
}

// Check that a field is named only once in INSERT or UPDATE statements.
static void dsqlFieldAppearsOnce(const Array<NestConst<ValueExprNode> >& values, const char* command)