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The idea of coding IN operator with a short list on the RHS as an OR expression

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turns out to be helpful.  If the list is of length 1 or 2, the OR expression
is very slightly faster, but the ephemeral table approach is clearly better for
all list lengths greater than 2.  Better to keep the code simple.

FossilOrigin-Name: e13175d3579e1045165bab091b3b28951d691704
This commit is contained in:
drh
2014-08-01 15:34:36 +00:00
parent 3a85625d87
commit e80c9b9ad5
4 changed files with 13 additions and 26 deletions
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14
src/expr.c
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@@ -1494,8 +1494,6 @@ int sqlite3CodeOnce(Parse *pParse){
** IN_INDEX_INDEX_DESC - The cursor was opened on a descending index.
** IN_INDEX_EPH - The cursor was opened on a specially created and
** populated epheremal table.
** IN_INDEX_NOOP - No cursor was allocated. The in operator must be
** implemented as a sequence of comparisons.
**
** An existing b-tree might be used if the RHS expression pX is a simple
** subquery such as:
@@ -1525,13 +1523,6 @@ int sqlite3CodeOnce(Parse *pParse){
** be used unless <column> is an INTEGER PRIMARY KEY or an index can
** be found with <column> as its left-most column.
**
** If the IN_INDEX_NOOP_OK and IN_INDEX_MEMBERSHIP are both set and
** if the RHS of the IN operator is a list (not a subquery) then this
** routine might decide that creating an ephemeral b-tree for membership
** testing is too expensive and return IN_INDEX_NOOP. IN that case, the
** calling routine should implement the IN operator using a sequence
** of Eq or Ne comparison operations.
**
** When the b-tree is being used for membership tests, the calling function
** might need to know whether or not the RHS side of the IN operator
** contains a NULL. If prNotFound is not NULL and
@@ -1939,7 +1930,7 @@ static void sqlite3ExprCodeIN(
v = pParse->pVdbe;
assert( v!=0 ); /* OOM detected prior to this routine */
VdbeNoopComment((v, "begin IN expr"));
eType = sqlite3FindInIndex(pParse, pExpr, 0,
eType = sqlite3FindInIndex(pParse, pExpr, IN_INDEX_MEMBERSHIP,
destIfFalse==destIfNull ? 0 : &rRhsHasNull);
/* Figure out the affinity to use to create a key from the results
@@ -1986,7 +1977,8 @@ static void sqlite3ExprCodeIN(
** contains one or more NULL values, then the result of the
** expression is also NULL.
*/
if( rRhsHasNull==0 || destIfFalse==destIfNull ){
assert( destIfFalse!=destIfNull || rRhsHasNull==0 );
if( rRhsHasNull==0 ){
/* This branch runs if it is known at compile time that the RHS
** cannot contain NULL values. This happens as the result
** of a "NOT NULL" constraint in the database schema.