Hello,
we are experiencing a problem with SQLite 3.7.9 where 213 Mb (!) are
allocated for the following query:
SELECT "partBody" IS NULL AS "partBodyIsNull" FROM LocalMailContents;
The database has a table LocalMailContents with several text / integer
columns and two BLOB columns at the end ("partHeader" and "partBody"). Both
of the blob columns either contain NULL or a value created by zeroblob()
function and later filled by the blob API. In our tests the last column is
filled with large data, specifically about 213 Mb. SQLite actually tries to
read the data when evaluating the above query and moreover it reads all the
data into a single memory chunk.
The code that is responsible for the read is in OP_Column:
if( u.am.aOffset[u.am.p2] ){
assert( rc==SQLITE_OK );
if( u.am.zRec ){
MemReleaseExt(u.am.pDest);
sqlite3VdbeSerialGet((u8 *)&u.am.zRec[u.am.aOffset[u.am.p2]],
u.am.aType[u.am.p2], u.am.pDest);
}else{
u.am.len = sqlite3VdbeSerialTypeLen(u.am.aType[u.am.p2]);
sqlite3VdbeMemMove(&u.am.sMem, u.am.pDest);
rc = sqlite3VdbeMemFromBtree(u.am.pCrsr, u.am.aOffset[u.am.p2],
u.am.len, u.am.pC->isIndex, &u.am.sMem);
if( rc!=SQLITE_OK ){
goto op_column_out;
}
u.am.zData = u.am.sMem.z;
sqlite3VdbeSerialGet((u8*)u.am.zData, u.am.aType[u.am.p2],
u.am.pDest);
}
u.am.pDest->enc = encoding;
}else{
A test database is available at
http://www.emclient.com/temp/mail_data.zipthat exhibits the behavior.
Is this something that is intended behavior? Is the memory allocation
really necessary?
Best regards,
Filip Navara
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