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t = db.distinct_index1;
t.drop();
function r( x ){
return Math.floor( Math.sqrt( x * 123123 ) ) % 10;
}
function d( k , q ){
return t.runCommand( "distinct" , { key : k , query : q || {} } );
}
for ( i=0; i<1000; i++ ){
o = { a : r(i*5) , b : r(i) };
t.insert( o );
}
x = d( "a" );
// Collection scan looks at all 1000 documents and gets 1000
// distinct values. Looks at 0 index keys.
assert.eq( 1000 , x.stats.n , "AA1" );
assert.eq( 0 , x.stats.nscanned , "AA2" );
assert.eq( 1000 , x.stats.nscannedObjects , "AA3" );
x = d( "a" , { a : { $gt : 5 } } );
// Collection scan looks at all 1000 documents and gets 398
// distinct values which match the query. Looks at 0 index keys.
assert.eq( 398 , x.stats.n , "AB1" );
assert.eq( 0 , x.stats.nscanned , "AB2" );
assert.eq( 1000 , x.stats.nscannedObjects , "AB3" );
x = d( "b" , { a : { $gt : 5 } } );
// Collection scan looks at all 1000 documents and gets 398
// distinct values which match the query. Looks at 0 index keys.
assert.eq( 398 , x.stats.n , "AC1" );
assert.eq( 0 , x.stats.nscanned , "AC2" );
assert.eq( 1000 , x.stats.nscannedObjects , "AC3" );
t.ensureIndex( { a : 1 } );
x = d( "a" );
// There are only 10 values. We use the fast distinct hack and only examine each value once.
assert.eq( 10 , x.stats.n , "BA1" );
assert.eq( 10 , x.stats.nscanned , "BA2" );
x = d( "a" , { a : { $gt : 5 } } );
// Only 4 values of a are >= 5 and we use the fast distinct hack.
assert.eq(4, x.stats.n , "BB1" );
assert.eq(4, x.stats.nscanned , "BB2" );
assert.eq(0, x.stats.nscannedObjects , "BB3" );
x = d( "b" , { a : { $gt : 5 } } );
// We can't use the fast distinct hack here because we're distinct-ing over 'b'.
assert.eq( 398 , x.stats.n , "BC1" );
assert.eq( 398 , x.stats.nscanned , "BC2" );
assert.eq( 398 , x.stats.nscannedObjects , "BC3" );
// Check proper nscannedObjects count when using a query optimizer cursor.
t.dropIndexes();
t.ensureIndex( { a : 1, b : 1 } );
x = d( "b" , { a : { $gt : 5 }, b : { $gt : 5 } } );
printjson(x);
// 171 is the # of results we happen to scan when we don't use a distinct
// hack. When we use the distinct hack we scan 16, currently.
assert.lte(x.stats.n, 171);
assert.eq(171, x.stats.nscannedObjects , "BD3" );
// Should use an index scan over the hashed index.
t.dropIndexes();
t.ensureIndex( { a : "hashed" } );
x = d( "a", { $or : [ { a : 3 }, { a : 5 } ] } );
assert.eq( 188, x.stats.n, "DA1" );
assert.eq( "IXSCAN { a: \"hashed\" }", x.stats.planSummary );
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