SQL-запрос из Битрикса

SELECT DISTINCT B.TYPE_SID, B.ID BANNER_ID, B.WEIGHT BANNER_WEIGHT,
B.SHOWS_FOR_VISITOR, B.FIX_CLICK, B.FIX_SHOW, B.KEYWORDS BANNER_KEYWORDS,
C.ID CONTRACT_ID, C.WEIGHT CONTRACT_WEIGHT, C.KEYWORDS CONTRACT_KEYWORDS
FROM b_adv_type T
INNER JOIN b_adv_banner B ON ( B.ACTIVE='Y' and B.TYPE_SID = T.SID
and B.STATUS_SID = 'PUBLISHED'
and (B.FOR_NEW_GUEST is null or B.FOR_NEW_GUEST='N')
and (ifnull(B.MAX_SHOW_COUNT,0)>ifnull(B.SHOW_COUNT,0)
or ifnull(B.MAX_SHOW_COUNT,0)=0) and (ifnull(B.MAX_CLICK_COUNT,0)>ifnull(B.CLICK_COUNT,0)
or ifnull(B.MAX_CLICK_COUNT,0)=0) and (ifnull(B.MAX_VISITOR_COUNT,0)>ifnull(B.VISITOR_COUNT,0)
or ifnull(B.MAX_VISITOR_COUNT,0)=0) and (B.DATE_SHOW_FROM<=now() or B.DATE_SHOW_
FROM is null or length(B.DATE_SHOW_FROM)<=0) and (B.DATE_SHOW_TO>=now()
or B.DATE_SHOW_TO is null or length(B.DATE_SHOW_TO)<=0))
INNER JOIN b_adv_banner_2_site BS ON ( BS.BANNER_ID = B.ID and BS.SITE_ID = 'ru')
INNER JOIN b_adv_contract C ON ( C.ID = B.CONTRACT_ID and C.ACTIVE='Y'
and (ifnull(C.MAX_SHOW_COUNT,0)>ifnull(C.SHOW_COUNT,0)
or ifnull(C.MAX_SHOW_COUNT,0)=0) and (ifnull(C.MAX_CLICK_COUNT,0)>ifnull(C.CLICK_COUNT,0)
or ifnull(C.MAX_CLICK_COUNT,0)=0)  and (ifnull(C.MAX_VISITOR_COUNT,0)>ifnull(C.VISITOR_COUNT,0)
or ifnull(C.MAX_VISITOR_COUNT,0)=0) and (C.DATE_SHOW_FROM<=now() or C.DATE_SHOW_
FROM is null or length(C.DATE_SHOW_FROM)<=0) and (C.DATE_SHOW_TO>=now()
or C.DATE_SHOW_TO is null or length(C.DATE_SHOW_TO)<=0))
INNER JOIN b_adv_contract_2_site CS ON ( CS.CONTRACT_ID = B.CONTRACT_ID and CS.SITE_ID = 'ru')
INNER JOIN b_adv_contract_2_type CT ON ( CT.CONTRACT_ID = C.ID
and (CT.TYPE_SID = 'ALL' or CT.TYPE_SID = T.SID))
INNER JOIN b_adv_banner_2_weekday BW ON ( BW.BANNER_ID = B.ID
and BW.C_WEEKDAY='SUNDAY' and BW.C_HOUR = '11')
INNER JOIN b_adv_contract_2_weekday CW ON ( CW.CONTRACT_ID = C.ID
and CW.C_WEEKDAY='SUNDAY' and CW.C_HOUR = '11')
LEFT JOIN b_adv_banner_2_group UG1 ON ( (UG1.BANNER_ID = B.ID and UG1.GROUP_ID in (2,1,21)) )
LEFT JOIN b_adv_banner_2_page BP1 ON ( BP1.BANNER_ID = B.ID and BP1.SHOW_ON_PAGE='Y')
LEFT JOIN b_adv_banner_2_page BP2 ON ( BP2.BANNER_ID = B.ID and BP2.SHOW_ON_PAGE='N'
and '/e-store/books/index.php?SECTION_ID=145' like concat(BP2.PAGE, '%'))
LEFT JOIN b_adv_contract_2_page CP1 ON ( CP1.CONTRACT_ID = C.ID and CP1.SHOW_ON_PAGE='Y')
LEFT JOIN b_adv_contract_2_page CP2 ON ( CP2.CONTRACT_ID = C.ID and CP2.SHOW_ON_PAGE='N'
and '/e-store/books/index.php?SECTION_ID=145' like concat(CP2.PAGE, '%'))
LEFT JOIN b_adv_banner_2_stat_adv BA ON BA.BANNER_ID = B.ID
LEFT JOIN b_adv_banner_2_country BC ON BC.BANNER_ID = B.ID WHERE T.ACTIVE = 'Y'
and BP2.ID is null and CP2.ID is null
and (BP1.ID is null or '/e-store/books/index.php?SECTION_ID=145' like concat(BP1.PAGE, '%'))
and (CP1.ID is null or '/e-store/books/index.php?SECTION_ID=145' like concat(CP1.PAGE, '%'))
and (BA.STAT_ADV_ID is null or BA.STAT_ADV_ID='0')
and (BC.COUNTRY_ID is null or BC.COUNTRY_ID='N0')
and ( (B.SHOW_USER_GROUP = 'Y' and UG1.GROUP_ID is not null)
or (B.SHOW_USER_GROUP <> 'Y' and UG1.GROUP_ID is null))
ORDER BY B.TYPE_SID desc, C.ID desc

У Битрикса одна из лучших админок, но внутри полный бардак. Как это работает на больших таблицах?
Например, не понятно зачем делать потенциально числовые поля строковыми: CP1.SHOW_ON_PAGE='Y'