Union all ItemsLimit pushdown

[Vladilen]

In a query like:

PRAGMA kikimr.KqpPushOlapProcess="true";
PRAGMA kikimr.OptEnablePredicateExtract="true";
PRAGMA kikimr.OptEnableOlapPushdownProjections="true";
PRAGMA OptimizeSimpleILIKE;
PRAGMA AnsiLike;
SELECT a,b,c
FROM `table1`
WHERE (`timestamp`) >= DateTime('2026-07-16T11:30:00Z') AND (`timestamp`) < DateTime('2026-07-16T13:30:00Z')
AND (a >= 9) AND ( a <= 15)

UNION ALL

SELECT a,b,c
FROM `table2`
WHERE (`timestamp`) >= DateTime('2026-07-16T11:30:00Z') AND (`timestamp`) < DateTime('2026-07-16T13:30:00Z')
AND (a >= 9) AND ( a <= 15)

ORDER BY `timestamp` DESC

LIMIT 10;

Limit 10 is not pushdowned to ColumnShard and CS reads all data.

If I run each query separately, ItemsLimit is pushdowned and CS returns early