{"id":14465,"date":"2022-10-07T23:14:49","date_gmt":"2022-10-07T17:44:49","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-ef-sql-query-performance-on-comma-separated-string-ids\/"},"modified":"2022-10-07T23:14:49","modified_gmt":"2022-10-07T17:44:49","slug":"solved-ef-sql-query-performance-on-comma-separated-string-ids","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-ef-sql-query-performance-on-comma-separated-string-ids\/","title":{"rendered":"[Solved] EF SQL query Performance on comma-separated string Ids"},"content":{"rendered":"

[ad_1]
\n<\/p>\n

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<\/div>\n
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If you store Ids as comma separated string – you always have TABLE\/INDEX scan. If your table is small it can be enough.<\/p>\n

With SecondaryTable<\/code> table which stores Ids associated with main table there a lot of other plans:<\/p>\n

    \n
  1. You can leave as is and trust or not DB Engine optimiser<\/li>\n<\/ol>\n
    query = query.Where(x => x.SecondaryTable.Any(s => s.Id == value));\n<\/code><\/pre>\n
      \n
    1. If pair (MainId, Id) is unique. The following query should definitely hit index<\/li>\n<\/ol>\n
      var query = \n   from m in query\n   from s in m.SecondaryTable.Where(s => s.Id == value)\n   select s;\n<\/code><\/pre>\n
        \n
      1. If pair (MainId, Id) is NOT unique.<\/li>\n<\/ol>\n
        var secondary = db.SecondaryTable.Where(s => s.Id == value);\nvar mainIds = secondary.Select(s => new { s.MainId }).Distinct();\n\nquery = \n   from m in query\n   from s in mainIds.Where(s => s.MainId == m.Id)\n   select m;\n<\/code><\/pre>\n
        Anyway, better to test and check execution plan.<\/p>\n<\/p><\/div>\n
        <\/div>\n<\/div>\n
                    0<\/span> <\/p><\/div>\n<\/div>\n
        [ad_2]<\/p>\n
        solved EF SQL query Performance on comma-separated string Ids <\/p>\n","protected":false},"excerpt":{"rendered":"
        [ad_1] If you store Ids as comma separated string – you always have TABLE\/INDEX scan. If your table is small it can be enough. With SecondaryTable table which stores Ids associated with main table there a lot of other plans: You can leave as is and trust or not DB Engine optimiser query = query.Where(x … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324,546,3791,578,500],"class_list":["post-14465","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-database","tag-entity-framework-core","tag-linq","tag-sql-server"],"yoast_head":"\n[Solved] EF SQL query Performance on comma-separated string Ids - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-ef-sql-query-performance-on-comma-separated-string-ids\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] EF SQL query Performance on comma-separated string Ids - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] If you store Ids as comma separated string – you always have TABLE\/INDEX scan. If your table is small it can be enough. With SecondaryTable table which stores Ids associated with main table there a lot of other plans: You can leave as is and trust or not DB Engine optimiser query = query.Where(x ... 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