PostgreSQL Query performance slow with Text column
PostgreSQL Query performance slower with Text column
我们正在使用 PostgreSQL 9.5.2
我们有 11 tables，每个 table
平均有 10K 条记录
其中一个 table 包含最大内容大小为 12K 个字符的文本列。
当我们从 select 语句中排除文本列时，大约需要 5 秒，而当我们包含文本列时，大约需要 55 秒。如果我们 select 来自同一 table 的任何其他列，它工作正常，但是一旦我们使用文本列，性能就会继续下降。
所有 table 都是内部连接的。
你能建议一下如何解决这个问题吗？
说明输出显示 378 毫秒，但实际上，获取这些数据大约需要 1 分钟。
所以当我们从 "ic" table 中排除文本列时，会在 4-5 秒内得到结果。
"Nested Loop Left Join (cost=4.04..156.40 rows=10 width=616) (actual time=3.092..377.128 rows=24118 loops=1)"
" -> Nested Loop Left Join (cost=3.90..59.92 rows=7 width=603) (actual time=2.834..110.842 rows=14325 loops=1)"
" -> Nested Loop Left Join (cost=3.76..58.56 rows=7 width=604) (actual time=2.832..101.481 rows=12340 loops=1)"
" -> Nested Loop (cost=3.62..57.19 rows=7 width=590) (actual time=2.830..90.614 rows=8436 loops=1)"
" Join Filter: (i."Id" = ic."ImId")"
" -> Nested Loop (cost=3.33..51.42 rows=7 width=210) (actual time=2.807..65.782 rows=8436 loops=1)"
" -> Nested Loop (cost=3.19..50.21 rows=7 width=187) (actual time=2.424..54.596 rows=8436 loops=1)"
" -> Nested Loop (cost=2.77..46.16 rows=7 width=175) (actual time=1.944..32.056 rows=8436 loops=1)"
" -> Nested Loop (cost=2.35..23.66 rows=5 width=87) (actual time=1.750..1.877 rows=4 loops=1)"
" -> Hash Join (cost=2.22..22.84 rows=5 width=55) (actual time=1.492..1.605 rows=4 loops=1)"
" Hash Cond: (i."ImtypId" = it."Id")"
" -> Nested Loop (cost=0.84..21.29 rows=34 width=51) (actual time=1.408..1.507 rows=30 loops=1)"
" -> Nested Loop (cost=0.56..9.68 rows=34 width=35) (actual time=1.038..1.053 rows=30 loops=1)"
" -> Index Only Scan using ev_query on "table_Ev" e (cost=0.28..4.29 rows=1 width=31) (actual time=0.523..0.523 rows=1 loops=1)"
" Index Cond: ("Id" = 1301)"
" Heap Fetches: 0"
" -> Index Only Scan using asmitm_query on "table_AsmItm" ai (cost=0.28..5.07 rows=31 width=8) (actual time=0.499..0.508 rows=30 loops=1)"
" Index Cond: (("AsmId" = e."AsmId") AND ("IsActive" = true))"
" Filter: "IsActive""
" Heap Fetches: 0"
" -> Index Only Scan using itm_query on "table_Itm" i (cost=0.28..0.33 rows=1 width=16) (actual time=0.014..0.014 rows=1 loops=30)"
" Index Cond: ("Id" = ai."ImId")"
" Heap Fetches: 0"
" -> Hash (cost=1.33..1.33 rows=4 width=12) (actual time=0.026..0.026 rows=4 loops=1)"
" Buckets: 1024 Batches: 1 Memory Usage: 9kB"
" -> Seq Scan on "ItmTyp" it (cost=0.00..1.33 rows=4 width=12) (actual time=0.013..0.018 rows=4 loops=1)"
" Filter: ("ParentId" = 12)"
" Rows Removed by Filter: 22"
" -> Index Only Scan using jur_query on "table_Jur" j (cost=0.14..0.15 rows=1 width=36) (actual time=0.065..0.066 rows=1 loops=4)"
" Index Cond: ("Id" = i."JurId")"
" Heap Fetches: 4"
" -> Index Scan using pwsres_evid_ImId_canid_query on "table_PwsRes" p (cost=0.42..3.78 rows=72 width=92) (actual time=0.056..6.562 rows=2109 loops=4)"
" Index Cond: (("EvId" = 1301) AND ("ImId" = i."Id"))"
" -> Index Only Scan using user_query on "table_User" u (cost=0.42..0.57 rows=1 width=16) (actual time=0.002..0.002 rows=1 loops=8436)"
" Index Cond: ("Id" = p."CanId")"
" Heap Fetches: 0"
" -> Index Only Scan using ins_query on "table_Ins" ins (cost=0.14..0.16 rows=1 width=31) (actual time=0.001..0.001 rows=1 loops=8436)"
" Index Cond: ("Id" = u."InsId")"
" Heap Fetches: 0"
" -> Index Scan using "IX_ItmCont_ImId" on "table_ItmCont" ic (cost=0.29..0.81 rows=1 width=392) (actual time=0.002..0.002 rows=1 loops=8436)"
" Index Cond: ("ImId" = p."ImId")"
" Filter: ("ContTyp" = 'CP'::text)"
" Rows Removed by Filter: 1"
" -> Index Scan using "IX_FreDetail_FreId" on "table_FreDetail" f (cost=0.14..0.18 rows=2 width=22) (actual time=0.000..0.001 rows=1 loops=8436)"
" Index Cond: ("FreId" = p."FreId")"
" -> Index Scan using "IX_DurDetail_DurId" on "table_DurDetail" d (cost=0.14..0.17 rows=2 width=7) (actual time=0.000..0.000 rows=0 loops=12340)"
" Index Cond: ("DurId" = p."DurId")"
" -> Index Scan using "IX_DruConsRouteDetail_DruConsRouId" on "table_DruConsRouDetail" dr (cost=0.14..0.18 rows=2 width=21) (actual time=0.001..0.001 rows=1 loops=14325)"
" Index Cond: ("DruConsRouteId" = p."RouteId")"
" SubPlan 1"
" -> Index Only Scan using asm_query on "table_Asm" (cost=0.14..8.16 rows=1 width=26) (actual time=0.001..0.001 rows=1 loops=24118)"
" Index Cond: ("Id" = e."AsmId")"
" Heap Fetches: 24118"
" SubPlan 2"
" -> Seq Scan on "ItmTyp" ity (cost=0.00..1.33 rows=1 width=4) (actual time=0.003..0.003 rows=1 loops=24118)"
" Filter: ("Id" = it."ParentId")"
" Rows Removed by Filter: 25"
"Planning time: 47.056 ms"
"Execution time: 378.229 ms"
如果解释分析输出花费 378 毫秒，这就是查询花费的时间，可能没有太多改进空间。如果传输和加载数据需要 1 分钟，则您需要为此努力。
如果您尝试在 psql 或 pgadmin 中查看非常宽的行，计算行宽或呈现 html 可能需要一些时间，但这与查询性能无关。
我们正在使用 PostgreSQL 9.5.2
我们有 11 tables，每个 table
平均有 10K 条记录其中一个 table 包含最大内容大小为 12K 个字符的文本列。
当我们从 select 语句中排除文本列时，大约需要 5 秒，而当我们包含文本列时，大约需要 55 秒。如果我们 select 来自同一 table 的任何其他列，它工作正常，但是一旦我们使用文本列，性能就会继续下降。 所有 table 都是内部连接的。
你能建议一下如何解决这个问题吗？
说明输出显示 378 毫秒，但实际上，获取这些数据大约需要 1 分钟。 所以当我们从 "ic" table 中排除文本列时，会在 4-5 秒内得到结果。
"Nested Loop Left Join (cost=4.04..156.40 rows=10 width=616) (actual time=3.092..377.128 rows=24118 loops=1)"
" -> Nested Loop Left Join (cost=3.90..59.92 rows=7 width=603) (actual time=2.834..110.842 rows=14325 loops=1)"
" -> Nested Loop Left Join (cost=3.76..58.56 rows=7 width=604) (actual time=2.832..101.481 rows=12340 loops=1)"
" -> Nested Loop (cost=3.62..57.19 rows=7 width=590) (actual time=2.830..90.614 rows=8436 loops=1)"
" Join Filter: (i."Id" = ic."ImId")"
" -> Nested Loop (cost=3.33..51.42 rows=7 width=210) (actual time=2.807..65.782 rows=8436 loops=1)"
" -> Nested Loop (cost=3.19..50.21 rows=7 width=187) (actual time=2.424..54.596 rows=8436 loops=1)"
" -> Nested Loop (cost=2.77..46.16 rows=7 width=175) (actual time=1.944..32.056 rows=8436 loops=1)"
" -> Nested Loop (cost=2.35..23.66 rows=5 width=87) (actual time=1.750..1.877 rows=4 loops=1)"
" -> Hash Join (cost=2.22..22.84 rows=5 width=55) (actual time=1.492..1.605 rows=4 loops=1)"
" Hash Cond: (i."ImtypId" = it."Id")"
" -> Nested Loop (cost=0.84..21.29 rows=34 width=51) (actual time=1.408..1.507 rows=30 loops=1)"
" -> Nested Loop (cost=0.56..9.68 rows=34 width=35) (actual time=1.038..1.053 rows=30 loops=1)"
" -> Index Only Scan using ev_query on "table_Ev" e (cost=0.28..4.29 rows=1 width=31) (actual time=0.523..0.523 rows=1 loops=1)"
" Index Cond: ("Id" = 1301)"
" Heap Fetches: 0"
" -> Index Only Scan using asmitm_query on "table_AsmItm" ai (cost=0.28..5.07 rows=31 width=8) (actual time=0.499..0.508 rows=30 loops=1)"
" Index Cond: (("AsmId" = e."AsmId") AND ("IsActive" = true))"
" Filter: "IsActive""
" Heap Fetches: 0"
" -> Index Only Scan using itm_query on "table_Itm" i (cost=0.28..0.33 rows=1 width=16) (actual time=0.014..0.014 rows=1 loops=30)"
" Index Cond: ("Id" = ai."ImId")"
" Heap Fetches: 0"
" -> Hash (cost=1.33..1.33 rows=4 width=12) (actual time=0.026..0.026 rows=4 loops=1)"
" Buckets: 1024 Batches: 1 Memory Usage: 9kB"
" -> Seq Scan on "ItmTyp" it (cost=0.00..1.33 rows=4 width=12) (actual time=0.013..0.018 rows=4 loops=1)"
" Filter: ("ParentId" = 12)"
" Rows Removed by Filter: 22"
" -> Index Only Scan using jur_query on "table_Jur" j (cost=0.14..0.15 rows=1 width=36) (actual time=0.065..0.066 rows=1 loops=4)"
" Index Cond: ("Id" = i."JurId")"
" Heap Fetches: 4"
" -> Index Scan using pwsres_evid_ImId_canid_query on "table_PwsRes" p (cost=0.42..3.78 rows=72 width=92) (actual time=0.056..6.562 rows=2109 loops=4)"
" Index Cond: (("EvId" = 1301) AND ("ImId" = i."Id"))"
" -> Index Only Scan using user_query on "table_User" u (cost=0.42..0.57 rows=1 width=16) (actual time=0.002..0.002 rows=1 loops=8436)"
" Index Cond: ("Id" = p."CanId")"
" Heap Fetches: 0"
" -> Index Only Scan using ins_query on "table_Ins" ins (cost=0.14..0.16 rows=1 width=31) (actual time=0.001..0.001 rows=1 loops=8436)"
" Index Cond: ("Id" = u."InsId")"
" Heap Fetches: 0"
" -> Index Scan using "IX_ItmCont_ImId" on "table_ItmCont" ic (cost=0.29..0.81 rows=1 width=392) (actual time=0.002..0.002 rows=1 loops=8436)"
" Index Cond: ("ImId" = p."ImId")"
" Filter: ("ContTyp" = 'CP'::text)"
" Rows Removed by Filter: 1"
" -> Index Scan using "IX_FreDetail_FreId" on "table_FreDetail" f (cost=0.14..0.18 rows=2 width=22) (actual time=0.000..0.001 rows=1 loops=8436)"
" Index Cond: ("FreId" = p."FreId")"
" -> Index Scan using "IX_DurDetail_DurId" on "table_DurDetail" d (cost=0.14..0.17 rows=2 width=7) (actual time=0.000..0.000 rows=0 loops=12340)"
" Index Cond: ("DurId" = p."DurId")"
" -> Index Scan using "IX_DruConsRouteDetail_DruConsRouId" on "table_DruConsRouDetail" dr (cost=0.14..0.18 rows=2 width=21) (actual time=0.001..0.001 rows=1 loops=14325)"
" Index Cond: ("DruConsRouteId" = p."RouteId")"
" SubPlan 1"
" -> Index Only Scan using asm_query on "table_Asm" (cost=0.14..8.16 rows=1 width=26) (actual time=0.001..0.001 rows=1 loops=24118)"
" Index Cond: ("Id" = e."AsmId")"
" Heap Fetches: 24118"
" SubPlan 2"
" -> Seq Scan on "ItmTyp" ity (cost=0.00..1.33 rows=1 width=4) (actual time=0.003..0.003 rows=1 loops=24118)"
" Filter: ("Id" = it."ParentId")"
" Rows Removed by Filter: 25"
"Planning time: 47.056 ms"
"Execution time: 378.229 ms"
如果解释分析输出花费 378 毫秒，这就是查询花费的时间，可能没有太多改进空间。如果传输和加载数据需要 1 分钟，则您需要为此努力。
如果您尝试在 psql 或 pgadmin 中查看非常宽的行，计算行宽或呈现 html 可能需要一些时间，但这与查询性能无关。