Retrieving data from Firebase , stored with UId key value
What is a NullPointerException, and how do I fix it?
Does "Going Infinite" necessarily end the game? Speeding up a NOT IN subquery Good evening,  I'm currently up to try to improve the performance of some of my queries. As far as I know, statements like "IN" or "NOT IN" are even faster with a large amount of values if a subquery on an indexed field without conditions is used.  SELECT * FROM table1 WHERE field1 NOT IN (SELECT index_field FROM table2)   When it comes to use conditions at table2, the query becomes realy slow on a large amount of data.  SELECT * FROM table1 WHERE     field1 NOT IN (         SELECT             index_field         FROM table2         WHERE             user_id = '2'     )   I was thinking about using LEFT Join but when I need to to the filtering for the user_id, it also becomes slow.  How may I solve this problem? Currently, I've no clue about that.  The original query looked sth. like this  SELECT     i.* FROM stream_item si LEFT JOIN user__publisher_item ui     ON ui.user_id = 2     &amp;&amp; ui.item_id = si.item_id INNER JOIN item i     ON i.id = si.item_id WHERE      si.stream_id IN (5,7,8,9,19,24,29,42,43,44)     &amp;&amp; ui.id IS NULL || (         ui.`read` = 0 || ui.saved = 1     ) GROUP BY     si.item_id ORDER BY     si.`found` DESC LIMIT 0,10     id      select_type     table   type        possible_keys                                                                           key                 key_len     ref                 rows        Extra 1       SIMPLE          si      index       PRIMARY,stream_2_item,stream_id_found                                                   stream_2_item       4           \N                  663236      Using temporary; Using filesort 1       SIMPLE          ui      eq_ref      user_id_item_id,user_2_item,user_id_read_saved_hidden,user_id_saved,user_id_hidden      user_id_item_id     8           const,si.item_id    1           Using where 1       SIMPLE          i       eq_ref      PRIMARY                                                                                 PRIMARY             4           si.item_id          1      I have a table which represents the n:m relationship between stream and items. An unique item can be accessible via multiple streams. Based upon this i have a state-table for user dependent states of an item. Currently, the user-state-entry will only be generated, if the item was read or saved the first tim. Otherwise, there is no entry in the user_item table. In the beginning, this query was fine but now, it takes a lot of time. Even if I leave out the "INNER JOIN" it takes 7 seconds on the current tables with around 500k rows each.  The table-structure in the background is as follows:   stream stream_item //n:m relation between stream and items item //unique items stream_group //user-defined groups of multiple streams stream_group_streams //_n:m relation between stream_groups and streams_ user user_item //state-table that holds the user-dependent states of an item - if there is no state, no row exists for an item   I already asked this question at  but added my 2 Edits with further information to late so that I haven't got an answer anymore. How to remove ubuntu partitions and use them to install windows I'm curious why PCBs have one square pad in row for 0.1" headers. What is purpose of putting one square pad? What it indicates? Can you push more amps through square pad than round? How can I find out when Windows was last restarted? How can I know when my computer running Windows 7 was last restarted?   I prefer a solution that doesn't involve searching the event log, but something like wmic or maybe cmd commands. changed primary email in google account. how to log in? I added gmail to my google account. Now when i try to log into stack exchange using google it prompts me to create a new account instead of using the existing.   The google account is still the same but google changed the primary email adress.  How can i log in again? What are some practices for getting a name change so that people can find me more easily? For a similar thing, , where Jay Wacker managed to get people to call him by the name Jay even though he didn't need to get a legal name change. I'm not sure how to go about this though.  The main problem with me is that I have such a frustratingly common name that a lot of people cannot find me when they google me. So many of them simply don't notice the middle initial that I always use in between my first and last names, and this could actually become a major issue in academia, since people have little time and are prone to giving up quickly if they want to look for me (or for my papers) and can't find me at all (I know this having seen how several academics use the Internet and how they look for people's names). This, in turn, could easily ruin my citation count in the future (it's not just that - it's helpful to others when I have a less common name so that they can more easily locate my stuff). I already know at least several people who specifically told me that they tried to find my email but that they couldn't find it (and this isn't limited to just them - there are many, many more - including long-lost friends who have wanted to talk to me for a long time, but who couldn't find me due to said ultra-common name). Of course, people can go through the respective university directories, but how many people really do that? From my observations (when I've seen people look for someone else), very very few do it. Hell, there are even several people at my OWN university who share the same exact first+last name as me.  In Academia, this is even a bigger problem because the vast majority of your connections will be people who only vaguely recognize/know you, so they may know most of the search clues. Even a "full name" + university won't solve all the problems, because I may switch universities and people may only remember the old university that I was in. I'm also very very interdisciplinary, so I want to be searchable to people outside my field as well.  And even if I fix the issue for Google with a massive SEO operation or whatever (that may even be impossible for my ridiculously common name), it's still not going to fix the problem for all of the other ways that people use search.  I'm currently transitioning between undergrad and grad school, so now may be the perfect time for a name change? But I don't know what to do. Is it better for me to change my first name or my last name? The problem is that a citation like "Chen 2011" is going to produce so many entries that no one will ever find them, even though they frequently do google things like that (and I simply cannot prevent people from googling something like that). Chen is so frustratingly common that even a "Chen and Name2 2011" paper could come from some random medical paper rather than from something I wrote.  As an additional complication, the % of Chinese people using the English Internet is exponentially rising, and I can only expect the problem to get worse in the future because of that (and not just for my first name, but even variants of my first name too). Anvil, extra lines thingies Explaining different Standard Deviation results from same data in ArcGIS Desktop and MS Excel? I have done some interpolation in Geostatistical Analyst in ArcGIS and I got the Standard Deviation (SD) a bit different from the SD that I calculated in Excel Spreadsheet.   What algorithm does each package use? Why are the results different? Prove that the multiplicative inverse of $a$ modulo $m$ exists if and only if $a$ and $m$ are coprime.  Can someone help me with this? JavaScript object: access variable property by name as string I am trying to compile a list of the different ways to come up with the closed form for the sum in the title. So far I have the famous Gauss story, the argument by counting doubletons, and using generating functions. Is there any other (significantly) different way to discover the closed form?  To clarify, Gauss's method was to take $1+2+3+\dots+n$, write it backwards, and add it up. What is a "hat"? What exactly is a hat?  I have seen a lot of people arguing the significance of hats and the limited edition hats. I know the hats are sort of linked to the Winterbash stuff, but what exactly is a hat, what does it do, how do I get one?  Is there a full list of hats? Maximum and Minimum values for ints Wikipedia says that the name of concept comes from physics, but I cannot find any similarity between these two concepts. Async Await Handler Deadlock 35km commute possible? Currently, on every other day I commute to work which is a distance of 18km each way. I enjoy this ride but next year I may be moving to a place which will be about 35km from work. Questions:  1) Would it still be reasonable to commute this kind of distance each way once I have moved?  2) Google maps estimates that this distance would take 2 hours to complete. Would it be possible (depending on the bike and fitness) to do this distance in about an hour? Why (...) doesn't spawn a new child process when run in background? Displaying row/column of point in raster using QGIS? Is it possible in QGIS to display column and row index of pixel in raster?   I mean something similar to value tool. I recently upgraded my computer's RAM to 4&nbsp;GB. My 32-bit Windows installation shows only 3574&nbsp;MB of the memory. How can I make Windows use the full amount of RAM?