slow and jerky Graphics in 12.1 compared to older version 9.0

Consider the following piece of code

Manipulate[ Graphics[ {{Gray, Line@Table[RandomReal[1.5 {-1, 1}, {2, 2}], {10000}]}, Dynamic[Disk[{0.1 a Cos[a], 0.12 Sin[a]}, 0.1]]}, PlotRange -> 1.5, FrameTicks -> False, Frame -> True], {a, 0, 4 \[Pi]}] 

Running the above code I find that the Graphics in newer versions of Mathematica (e.g. version 12.1) are jerky and are rendered considerably slower. I ran the same code in version 9.0 and it runs relatively smoothly.

Does someone know why this is so? and what changed between the older and the newer versions of Mathematica?

What happens to a spell cast by a target affected by the delayed effect of the Slow spell when he saves?

Part of the description of the Slow spell says:

If the creature attempts to cast a spell with a casting time of 1 action, roll a d20. On an 11 or higher, the spell doesn’t take effect until the creature’s next turn, and the creature must use its action on that turn to complete the spell. If it can’t, the spell is wasted.

The affected spellcaster casts a spell and is hindered by the Slow spell so that his spell does not go off until his next turn, but he saves against the Slow spell at the end of his turn.

MySQL query is very slow (15 minutes)

I was previously using SQLite for a personal project and due to a constraint of having it available online, I decided to make the switch to MySQL. I converted my database to the MySQL equivalent but I just noticed that performance is VERY poor. This is a 70 mb database with around 600k records total. The query I am running is an INNER JOIN that executes in less than 500 ms using SQLite but the same query using MySQL takes 15 minutes.

SELECT has.tag_id, has.image_id FROM has INNER JOIN image ON image.image_id = has.image_id INNER JOIN person ON person.person_id = image.person_id WHERE person.name="Random Person" 
  • has table has 80k records
  • image table has 290k records
  • person table has 500 records

Here is the structure of the three tables:

create table media.person (     person_id int auto_increment         primary key,     name         text not null )     collate = utf8_unicode_ci;  create table media.image (     id           int auto_increment,     image_id     int  not null,     person_id int  not null,     link         text not null,     checksum     text null,     constraint id         unique (id) )     collate = utf8_unicode_ci;  alter table media.image     add primary key (id);  create table media.has (     id       int auto_increment         primary key,     tag_id   int not null,     image_id int not null )     collate = utf8_unicode_ci; 

Note that I added a primary key to the has table because I suspected it might have been the source of the problem, but it isn’t and SQLite was doing fine without that primary key.

The database uses the InnoDB engine. Here is the output of the mysql --version command:

mysql Ver 14.14 Distrib 5.7.30 

Where could the problem come from? I can understand a small loss of performance because MySQL is heavier than SQLite but certainly not to the point of going from 500 ms to 15 minutes for such a simple query.

0/1 Knapsack algorithm with memoization slow (C#) [closed]

I’m solving a knapsack problem here. It works, but gives time limit exceeds on a certain test case.


Problem statement

There are N items, numbered 1,2,…,N. For each i (1≤i≤N), Item i has a weight of wi and a value of vi

Taro has decided to choose some of the N items and carry them home in a knapsack. The capacity of the knapsack is W, which means that the sum of the weights of items taken must be at most W

Find the maximum possible sum of the values of items that Taro takes home.


The input is in the following form:

N W w1 v1 w2 v2 : wN vN 

N: Number of items.

W: Max weight I can have.

wi: ith weight.

vi: ith value.

Here is my solution to it:

using System; using System.Collections.Generic;  public static class Solution {   // Both s_weights and s_values will have the same length.   private static int[] s_weights; // array holding the weights of the items.   private static int[] s_values; // array holding the values of the items.   private static Dictionary<(int, int), long> s_memo; // memoization dictionary.    // NOTE: I cannot use an array instead of a dictionary here, cause it   // will be a very large 2d array and will give OutOfMemoryException.    public static void Main()   {     // Read the first line, which contains number of items and max weight.     string[] nw = Console.ReadLine().Split(' ');     // Parse n.     int n = int.Parse(nw[0]);     // Parse the max weight.     int maxWeight = int.Parse(nw[1]);      s_weights = new int[n];     s_values = new int[n];     // arbitrary high capacity dictionary to avoid resizing which is O(n).     s_memo = new Dictionary<(int, int), long>(10000000);      // Read each line from the input.     for (int i = 0; i < n; i++)     {       string[] wv = Console.ReadLine().Split(' ');       s_weights[i] = int.Parse(wv[0]);       s_values[i] = int.Parse(wv[1]);     }     // Start the recursion with the maximum weight and all the items.     Console.WriteLine(Solve(maxWeight, n));   }    private static long Solve(int weightLeft, int numberOfItemsToConsider)   {     // simple base case.     if (weightLeft == 0 || numberOfItemsToConsider == 0) return 0;      // If already calculated, get it from the dictionary.     if (s_memo.TryGetValue((weightLeft, numberOfItemsToConsider), out var cachedValue))     {       return cachedValue;     }      // Recursive call calculating the solution if we don't take the current item.     long dontTakeCurrent = Solve(weightLeft, numberOfItemsToConsider - 1);     long result;      // Can we take the current item? If yes, calculate the solution.     if (weightLeft >= s_weights[numberOfItemsToConsider - 1])     {       long takeCurrent = s_values[numberOfItemsToConsider - 1] + Solve(weightLeft - s_weights[numberOfItemsToConsider - 1], numberOfItemsToConsider - 1);       // Maximize the value between the two cases, taking or not taking the item.       result = Math.Max(takeCurrent, dontTakeCurrent);       // Add the result to the memo dictionary.       s_memo.Add((weightLeft, numberOfItemsToConsider), result);       return result;     }     // Here, we don't have another choice other than not taking the item.     result = dontTakeCurrent;     s_memo.Add((weightLeft, numberOfItemsToConsider), result);     return result;   }                           } 

Note: I’ve already asked the question in codereview but no answer until now, so I thought cs could be a better place to ask about it.

Slow Database with concurrent queries, Table cache hitrate 0% [Newbie! Need help :)]

I’m a bit of a newbie when it comes to dba work so please take it easy!

I have gone through countless threads trying to improve the performance of my database, looking for someone who could give me some pointers on changes I may need to do for my variables that may squeeze more performance. Or if I have misconfigured anything.

Here are the details Server specs: E3 1270 V6 w/32gb Ram OS: Windows Server 2016 Mysql Version: 8.0.19 – MySQL Community Server – GPL

MYSQL Config https://ybin.me/p/b99f994ad62c27ad#zvwS1+XGP6ZIZtKYdiMOySg+aYR85Qp3ciTvFr6q4mE=

Show Global Status (during high usage):

https://ybin.me/p/b74fae252e807749#F9+88tWsVo/hqHjKlnlnG1gEUwj7vlonLlYrUxXnThg=

SHOW ENGINE INNODB STATUS (During High Usage)

InnoDB       ===================================== 2020-05-17 16:57:16 0xa6c INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 7 seconds ----------------- BACKGROUND THREAD ----------------- srv_master_thread loops: 103908 srv_active, 0 srv_shutdown, 300397 srv_idle srv_master_thread log flush and writes: 0 ---------- SEMAPHORES ---------- OS WAIT ARRAY INFO: reservation count 42855 OS WAIT ARRAY INFO: signal count 37923 RW-shared spins 3053, rounds 3116, OS waits 59 RW-excl spins 6909, rounds 59455, OS waits 1320 RW-sx spins 99, rounds 1306, OS waits 25 Spin rounds per wait: 1.02 RW-shared, 8.61 RW-excl, 13.19 RW-sx ------------------------ LATEST DETECTED DEADLOCK ------------------------ 2020-05-17 13:52:00 0x2904 *** (1) TRANSACTION: TRANSACTION 12175899, ACTIVE 0 sec starting index read mysql tables in use 3, locked 3 LOCK WAIT 4 lock struct(s), heap size 1136, 3 row lock(s) MySQL thread id 3340, OS thread handle 3660, query id 2398670 localhost 127.0.0.1 root updating UPDATE user_inventory SET count = 22 WHERE identifier = 'steam:11000013f8eef2a' AND item = 'bandage'  *** (1) HOLDS THE LOCK(S): RECORD LOCKS space id 584 page no 84 n bits 336 index PRIMARY of table `essentialmode`.`user_inventory` trx id 12175899 lock_mode X locks rec but not gap Record lock, heap no 69 PHYSICAL RECORD: n_fields 6; compact format; info bits 0  0: len 4; hex 8039a49f; asc  9  ;;  1: len 6; hex 000000b9849a; asc       ;;  2: len 7; hex 02000001ad0151; asc       Q;;  3: len 21; hex 737465616d3a313130303030313366386565663261; asc steam:11000013f8eef2a;;  4: len 7; hex 62616e64616765; asc bandage;;  5: len 4; hex 8000002b; asc    +;;   *** (1) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 584 page no 2445 n bits 792 index item of table `essentialmode`.`user_inventory` trx id 12175899 lock_mode X waiting Record lock, heap no 561 PHYSICAL RECORD: n_fields 2; compact format; info bits 0  0: len 7; hex 62616e64616765; asc bandage;;  1: len 4; hex 800002e8; asc     ;;   *** (2) TRANSACTION: TRANSACTION 12175886, ACTIVE 0 sec fetching rows mysql tables in use 3, locked 3 LOCK WAIT 60 lock struct(s), heap size 8400, 2334 row lock(s) MySQL thread id 3336, OS thread handle 10296, query id 2398648 localhost 127.0.0.1 root updating UPDATE user_inventory SET count = 4 WHERE identifier = 'steam:11000010e1c050e' AND item = 'bandage'  *** (2) HOLDS THE LOCK(S): RECORD LOCKS space id 584 page no 2445 n bits 792 index item of table `essentialmode`.`user_inventory` trx id 12175886 lock_mode X Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0  0: len 8; hex 73757072656d756d; asc supremum;;  Record lock, heap no 561 PHYSICAL RECORD: n_fields 2; compact format; info bits 0  0: len 7; hex 62616e64616765; asc bandage;;  1: len 4; hex 800002e8; asc     ;;   *** (2) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 584 page no 84 n bits 336 index PRIMARY of table `essentialmode`.`user_inventory` trx id 12175886 lock_mode X locks rec but not gap waiting Record lock, heap no 69 PHYSICAL RECORD: n_fields 6; compact format; info bits 0  0: len 4; hex 8039a49f; asc  9  ;;  1: len 6; hex 000000b9849a; asc       ;;  2: len 7; hex 02000001ad0151; asc       Q;;  3: len 21; hex 737465616d3a313130303030313366386565663261; asc steam:11000013f8eef2a;;  4: len 7; hex 62616e64616765; asc bandage;;  5: len 4; hex 8000002b; asc    +;;  *** WE ROLL BACK TRANSACTION (1) ------------ TRANSACTIONS ------------ Trx id counter 12207888 Purge done for trx's n:o < 12207888 undo n:o < 0 state: running but idle History list length 19 LIST OF TRANSACTIONS FOR EACH SESSION: ---TRANSACTION 283609840283040, not started 0 lock struct(s), heap size 1136, 0 row lock(s) ---TRANSACTION 283609840282192, not started 0 lock struct(s), heap size 1136, 0 row lock(s) ---TRANSACTION 283609840281344, not started 0 lock struct(s), heap size 1136, 0 row lock(s) -------- FILE I/O -------- I/O thread 0 state: wait Windows aio (insert buffer thread) I/O thread 1 state: wait Windows aio (log thread) I/O thread 2 state: wait Windows aio (read thread) I/O thread 3 state: wait Windows aio (read thread) I/O thread 4 state: wait Windows aio (read thread) I/O thread 5 state: wait Windows aio (read thread) I/O thread 6 state: wait Windows aio (read thread) I/O thread 7 state: wait Windows aio (read thread) I/O thread 8 state: wait Windows aio (read thread) I/O thread 9 state: wait Windows aio (read thread) I/O thread 10 state: wait Windows aio (read thread) I/O thread 11 state: wait Windows aio (read thread) I/O thread 12 state: wait Windows aio (read thread) I/O thread 13 state: wait Windows aio (read thread) I/O thread 14 state: wait Windows aio (read thread) I/O thread 15 state: wait Windows aio (read thread) I/O thread 16 state: wait Windows aio (read thread) I/O thread 17 state: wait Windows aio (read thread) I/O thread 18 state: wait Windows aio (read thread) I/O thread 19 state: wait Windows aio (read thread) I/O thread 20 state: wait Windows aio (read thread) I/O thread 21 state: wait Windows aio (read thread) I/O thread 22 state: wait Windows aio (read thread) I/O thread 23 state: wait Windows aio (read thread) I/O thread 24 state: wait Windows aio (read thread) I/O thread 25 state: wait Windows aio (read thread) I/O thread 26 state: wait Windows aio (read thread) I/O thread 27 state: wait Windows aio (read thread) I/O thread 28 state: wait Windows aio (read thread) I/O thread 29 state: wait Windows aio (read thread) I/O thread 30 state: wait Windows aio (read thread) I/O thread 31 state: wait Windows aio (read thread) I/O thread 32 state: wait Windows aio (read thread) I/O thread 33 state: wait Windows aio (read thread) I/O thread 34 state: wait Windows aio (read thread) I/O thread 35 state: wait Windows aio (read thread) I/O thread 36 state: wait Windows aio (read thread) I/O thread 37 state: wait Windows aio (read thread) I/O thread 38 state: wait Windows aio (read thread) I/O thread 39 state: wait Windows aio (read thread) I/O thread 40 state: wait Windows aio (read thread) I/O thread 41 state: wait Windows aio (read thread) I/O thread 42 state: wait Windows aio (read thread) I/O thread 43 state: wait Windows aio (read thread) I/O thread 44 state: wait Windows aio (read thread) I/O thread 45 state: wait Windows aio (read thread) I/O thread 46 state: wait Windows aio (read thread) I/O thread 47 state: wait Windows aio (read thread) I/O thread 48 state: wait Windows aio (read thread) I/O thread 49 state: wait Windows aio (read thread) I/O thread 50 state: wait Windows aio (read thread) I/O thread 51 state: wait Windows aio (read thread) I/O thread 52 state: wait Windows aio (read thread) I/O thread 53 state: wait Windows aio (read thread) I/O thread 54 state: wait Windows aio (read thread) I/O thread 55 state: wait Windows aio (read thread) I/O thread 56 state: wait Windows aio (read thread) I/O thread 57 state: wait Windows aio (read thread) I/O thread 58 state: wait Windows aio (read thread) I/O thread 59 state: wait Windows aio (read thread) I/O thread 60 state: wait Windows aio (read thread) I/O thread 61 state: wait Windows aio (read thread) I/O thread 62 state: wait Windows aio (read thread) I/O thread 63 state: wait Windows aio (read thread) I/O thread 64 state: wait Windows aio (read thread) I/O thread 65 state: wait Windows aio (read thread) I/O thread 66 state: wait Windows aio (write thread) I/O thread 67 state: wait Windows aio (write thread) I/O thread 68 state: wait Windows aio (write thread) I/O thread 69 state: wait Windows aio (write thread) I/O thread 70 state: wait Windows aio (write thread) I/O thread 71 state: wait Windows aio (write thread) I/O thread 72 state: wait Windows aio (write thread) I/O thread 73 state: wait Windows aio (write thread) I/O thread 74 state: wait Windows aio (write thread) I/O thread 75 state: wait Windows aio (write thread) I/O thread 76 state: wait Windows aio (write thread) I/O thread 77 state: wait Windows aio (write thread) I/O thread 78 state: wait Windows aio (write thread) I/O thread 79 state: wait Windows aio (write thread) I/O thread 80 state: wait Windows aio (write thread) I/O thread 81 state: wait Windows aio (write thread) I/O thread 82 state: wait Windows aio (write thread) I/O thread 83 state: wait Windows aio (write thread) I/O thread 84 state: wait Windows aio (write thread) I/O thread 85 state: wait Windows aio (write thread) I/O thread 86 state: wait Windows aio (write thread) I/O thread 87 state: wait Windows aio (write thread) I/O thread 88 state: wait Windows aio (write thread) I/O thread 89 state: wait Windows aio (write thread) I/O thread 90 state: wait Windows aio (write thread) I/O thread 91 state: wait Windows aio (write thread) I/O thread 92 state: wait Windows aio (write thread) I/O thread 93 state: wait Windows aio (write thread) I/O thread 94 state: wait Windows aio (write thread) I/O thread 95 state: wait Windows aio (write thread) I/O thread 96 state: wait Windows aio (write thread) I/O thread 97 state: wait Windows aio (write thread) I/O thread 98 state: wait Windows aio (write thread) I/O thread 99 state: wait Windows aio (write thread) I/O thread 100 state: wait Windows aio (write thread) I/O thread 101 state: wait Windows aio (write thread) I/O thread 102 state: wait Windows aio (write thread) I/O thread 103 state: wait Windows aio (write thread) I/O thread 104 state: wait Windows aio (write thread) I/O thread 105 state: wait Windows aio (write thread) I/O thread 106 state: wait Windows aio (write thread) I/O thread 107 state: wait Windows aio (write thread) I/O thread 108 state: wait Windows aio (write thread) I/O thread 109 state: wait Windows aio (write thread) I/O thread 110 state: wait Windows aio (write thread) I/O thread 111 state: wait Windows aio (write thread) I/O thread 112 state: wait Windows aio (write thread) I/O thread 113 state: wait Windows aio (write thread) I/O thread 114 state: wait Windows aio (write thread) I/O thread 115 state: wait Windows aio (write thread) I/O thread 116 state: wait Windows aio (write thread) I/O thread 117 state: wait Windows aio (write thread) I/O thread 118 state: wait Windows aio (write thread) I/O thread 119 state: wait Windows aio (write thread) I/O thread 120 state: wait Windows aio (write thread) I/O thread 121 state: wait Windows aio (write thread) I/O thread 122 state: wait Windows aio (write thread) I/O thread 123 state: wait Windows aio (write thread) I/O thread 124 state: wait Windows aio (write thread) I/O thread 125 state: wait Windows aio (write thread) I/O thread 126 state: wait Windows aio (write thread) I/O thread 127 state: wait Windows aio (write thread) I/O thread 128 state: wait Windows aio (write thread) I/O thread 129 state: wait Windows aio (write thread) Pending normal aio reads: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] , aio writes: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] ,  ibuf aio reads:, log i/o's:, sync i/o's: Pending flushes (fsync) log: 0; buffer pool: 0 25639 OS file reads, 5252794 OS file writes, 2142145 OS fsyncs 0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s ------------------------------------- INSERT BUFFER AND ADAPTIVE HASH INDEX ------------------------------------- Ibuf: size 1, free list len 30, seg size 32, 78 merges merged operations:  insert 89, delete mark 3, delete 0 discarded operations:  insert 0, delete mark 0, delete 0 Hash table size 4425293, node heap has 577 buffer(s) Hash table size 4425293, node heap has 7 buffer(s) Hash table size 4425293, node heap has 3 buffer(s) Hash table size 4425293, node heap has 42 buffer(s) Hash table size 4425293, node heap has 25 buffer(s) Hash table size 4425293, node heap has 8 buffer(s) Hash table size 4425293, node heap has 117 buffer(s) Hash table size 4425293, node heap has 268 buffer(s) 63.71 hash searches/s, 4.29 non-hash searches/s --- LOG --- Log sequence number          8204611911 Log buffer assigned up to    8204611911 Log buffer completed up to   8204611911 Log written up to            8204611911 Log flushed up to            8204611911 Added dirty pages up to      8204611911 Pages flushed up to          8204611911 Last checkpoint at           8204611911 2113740 log i/o's done, 0.00 log i/o's/second ---------------------- BUFFER POOL AND MEMORY ---------------------- Total large memory allocated 17582522368 Dictionary memory allocated 1618261 Buffer pool size   1048576 Free buffers       1010227 Database pages     37302 Old database pages 13779 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 1961, not young 12509 0.00 youngs/s, 0.00 non-youngs/s Pages read 25245, created 12063, written 2341874 0.00 reads/s, 0.00 creates/s, 0.00 writes/s Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 37302, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---------------------- INDIVIDUAL BUFFER POOL INFO ---------------------- ---BUFFER POOL 0 Buffer pool size   131072 Free buffers       126195 Database pages     4738 Old database pages 1766 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 47, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 3177, created 1561, written 390400 0.00 reads/s, 0.00 creates/s, 0.00 writes/s Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4738, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---BUFFER POOL 1 Buffer pool size   131072 Free buffers       126202 Database pages     4747 Old database pages 1732 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 57, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 3144, created 1603, written 377393 0.00 reads/s, 0.00 creates/s, 0.00 writes/s Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4747, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---BUFFER POOL 2 Buffer pool size   131072 Free buffers       126359 Database pages     4584 Old database pages 1682 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 1596, not young 12509 0.00 youngs/s, 0.00 non-youngs/s Pages read 3159, created 1431, written 286695 0.00 reads/s, 0.00 creates/s, 0.00 writes/s No buffer pool page gets since the last printout Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4584, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---BUFFER POOL 3 Buffer pool size   131072 Free buffers       126376 Database pages     4563 Old database pages 1679 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 23, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 3060, created 1503, written 217282 0.00 reads/s, 0.00 creates/s, 0.00 writes/s No buffer pool page gets since the last printout Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4563, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---BUFFER POOL 4 Buffer pool size   131072 Free buffers       126427 Database pages     4515 Old database pages 1683 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 39, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 3113, created 1402, written 296757 0.00 reads/s, 0.00 creates/s, 0.00 writes/s Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4515, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---BUFFER POOL 5 Buffer pool size   131072 Free buffers       126346 Database pages     4604 Old database pages 1681 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 48, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 3120, created 1484, written 220370 0.00 reads/s, 0.00 creates/s, 0.00 writes/s Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4604, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---BUFFER POOL 6 Buffer pool size   131072 Free buffers       126053 Database pages     4883 Old database pages 1815 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 104, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 3276, created 1607, written 259821 0.00 reads/s, 0.00 creates/s, 0.00 writes/s Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4883, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] ---BUFFER POOL 7 Buffer pool size   131072 Free buffers       126269 Database pages     4668 Old database pages 1741 Modified db pages  0 Pending reads      0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 47, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 3196, created 1472, written 293156 0.00 reads/s, 0.00 creates/s, 0.00 writes/s Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 4668, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] -------------- ROW OPERATIONS -------------- 0 queries inside InnoDB, 0 queries in queue 0 read views open inside InnoDB Process ID=9652, Main thread ID=00000000000028B4 , state=sleeping Number of rows inserted 425605, updated 1126794, deleted 24758, read 3734292042 0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s Number of system rows inserted 1841, updated 1056, deleted 1656, read 1362568 0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 69.28 reads/s ---------------------------- END OF INNODB MONITOR OUTPUT ============================ 

MYSQL Tuner Tips https://i.gyazo.com/107f94f2e69fafe58d6f2125ff3c9ccc.png

I would highly appreciate any input on how we can make the database happier! If I’m missing any information, let me know happy to provide any extra info!

Extremely slow site!

Can anyone tell what's going on here?

This is a new WordPress installation, one-page site. I'm using Smush on the images and WP Super Cache. Images are a total of about 1300KB a think. It's hosted on GoDaddy (unfortunately).

Pingdom's latest test said it loaded in 2.5 seconds, but it took about 10 to load from my computer. The site has a 1400 ms wait time.

http://www.jfblawaz.com/

Plot of Piecewise function is slow

While working on answer for question (here) I found out that the Plot is incredible slow for Piecewise function:

Some preparations:

\[ScriptCapitalD]1 =   TransformedDistribution[Log[u],    u \[Distributed] UniformDistribution[{1, 2}]] (* TransformedDistribution[  Log[\[FormalX]], \[FormalX] \[Distributed]    UniformDistribution[{1, 2}]] *)  \[ScriptCapitalD] =   TransformedDistribution[   u + v, {u \[Distributed] UniformDistribution[{1, 2}],     v \[Distributed] \[ScriptCapitalD]1}] (* TransformedDistribution[  u + v, {u \[Distributed] UniformDistribution[{1, 2}],    v \[Distributed]     TransformedDistribution[     Log[\[FormalX]], \[FormalX] \[Distributed]       UniformDistribution[{1, 2}]]}] *) 

This looks perfectly fine:

s[x_] := PDF[\[ScriptCapitalD], x]     pw[x_] := PiecewiseExpand[s[x], 1 <= x <= 2] pw[x] // InputForm (* Piecewise[{{1, x >= 1 + Log[2]}, {(-E + E^x)/E, Inequality[1, Less, x, Less,      1 + Log[2]]}}, 0] *) 

But, the Plot is extremely slow and never finishes:

Plot[pw[x], {x, 1, 2}] 

But, if I copy InputForm of pw, it magically started working:

pw2[x_] :=   Piecewise[{{1, x >= 1 + Log[2]}, {(-E + E^x)/E,      Inequality[1, Less, x, Less, 1 + Log[2]]}}, 0]  Plot[pw2[x], {x, 1, 2}] (* produces plot *) 

Using Mathematica 12.1.

Querying a table with 200+ million rows by filtering on the clustered index AND additional column is super slow

We have one table that has clustered index on two columns: first one is NVARCHAR(50) and second one is on DATETIME2(3) type.

There are few other columns. When we query the table with WHERE clause on the clustered index columns, the result is received immediately, even when the result set is tens of thousands of rows.

However, if we add one more predicate on the where clause, the query is super slow. After ten seconds I just stop it, because that is not useful to us.

The table has 200+ million rows.

This is the query that is super fast:

SELECT * FROM Table WHERE Col1 = 'blah' AND Col2 BETWEEN 'date1' AND 'date2' 

This is the query that is super slow:

SELECT * FROM Table WHERE Col1 = 'blah' AND Col2 BETWEEN 'date1' AND 'date2' AND BooleanColumn = 1 

In my mind, the second query should use the clustered index to search for rows and then simply scan the result set to filter out what’s needed.

Is it possible to (somehow) make the second query work fast without creating additional non clustered index that would include other columns that we need to filter on?