Details
Minor - P4 Description
If NamespaceDetails::getRecordAllocationSize() is passed a value that is a power of 2, and Flag_UsePowerOf2Sizes is enabled, the function will return the next power of two (or the next 1mb increment if >= 4mb).
This is only an issue in (potentially rare) cases when getRecordAllocationSize() is passed a value that is already quantized.
Test
c = db.c;
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c.drop();
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db.createCollection( 'c' );
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printjson( db.runCommand( { collMod:'c', usePowerOf2Sizes:true } ) );
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big = new Array( 1024 * 1024 - 41 ).toString();
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doc = { _id:0, b:big };
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assert.eq( 0x100000 - 0x10, Object.bsonsize( doc ) );
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// A doc of size 0x100000 - 0x10 triggers a record allocation request of size 0x100000.
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c.insert( doc );
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// But the actual record size allocated is 0x200000. This can be seen by adding logging.
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printjson( c.dataSize() ); // 0x200000 - 0x10
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c.drop();
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db.createCollection( 'c' );
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printjson( db.runCommand( { collMod:'c', usePowerOf2Sizes:true } ) );
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big = new Array( 16 * 1024 * 1024 - 41 ).toString();
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doc = { _id:0, b:big };
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assert.eq( 0x1000000 - 0x10, Object.bsonsize( doc ) );
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// A doc of size 0x1000000 - 0x10 triggers a record allocation request of size 0x1000000.
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c.insert( doc );
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// But the actual record size allocated is 0x1100000. This can be seen by adding logging.
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printjson( c.dataSize() ); // 0x1100000 - 0x10
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