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PONeed for long and dynamic select query/view sqlite
 

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  1. PONeed for long and dynamic select query/view sqlite
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    <p>I have a need to generate a long select query of potentially thousands of <code>where</code> conditions like <code>(table1.a = ? OR table1.a = ? OR ...) AND (table2.b = ? OR table2.b = ? ...) AND....</code></p> <p>I initially started building a class to make this more bearable, but have since stopped to wonder if this will work well. This query is going to be hammering a table of potentially 10s of millions of rows joined with 2 more tables with thousands of rows.</p> <p>A number of concerns are stemming from this:</p> <p>1.) I wanted to use these statements to generate a temp view so I could easily transfer over existing code base, the point here is I want to filter data that I have down for analysis based on selected parameters in a GUI, so how poorly will a view do in this scenario?</p> <p>2.) Can sqlite even parse a query with thousands of binds?</p> <p>3.) Isn't there a framework that can make generating this query easier other than with string concatenation?</p> <p>4.) Is the better solution to dump all of the WHERE variables into hash sets in memory and then just write a wrapper for my DB query object that gets <code>next()</code> until a query is encountered this satisfies all my conditions? My concern here is, the application generates graphs procedurally on scrolls, so waiting to draw while calling <code>query.next()</code> x 100,000 might cause an annoying delay? Ideally I don't want to have to wait on the next row that satisfies everything for more than 30ms at a time.</p> <p>edit:</p> <p>New issue, it came to my attention that sqlite3 is limited to 999 bind values(host parameters) at compile time.</p> <p>So it seems as if the only way to accomplish what I had originally intended is to</p> <p>1.) Generate the entire query via string concatenations(my biggest concern being, I don't know how slow parsing all the data inside sqlite3 will be)</p> <p>or</p> <p>2.) Do the blanket query method(<code>select * from * where index &gt; ? limit ?</code>) and call next() until I hit what valid data in my compiled code(including updating index variable and re-querying repeatedly)</p> <p>I did end up writing a wrapper around the QSqlQuery object that will walk a table using index > variable and limit to allow "walking" the table.</p>
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    1. USJohn Lotacs
    1. USJohn Lotacs
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      1. VTUpMod
    1. COYou want to use the "in" statement rather than a bunch of "="s.
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      1. PONeed for long and dynamic select query/view sqlite
      1. USGordon Linoff
    2. COI guess, but the rest of my concerns still stand.
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      1. PONeed for long and dynamic select query/view sqlite
      1. USJohn Lotacs
    3. COStop thinking in "row at a time" patterns. For a database it is much easier to select all the tuples that satisfy a condition, than to pick them one-by-one. What is the source of your `where field In (...)` list. Do you perform two queries for one goal? (one to get the keys, the second for the actual contents)
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      1. USwildplasser
 

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