Strange query execution time

<font size="3">Hi,<br /><br /> Can  someone explain why the following query takes  1 second when using LIKE and takes
30seconds when replacing LIKE by = in the WHERE ?<br /> - instance_Attribute  has 45 rows and Influence has 5 rows.<br
/>- Postgresql 7.1<br /><br /> Regards<br /> =====================================<br /> SELECT <br />
E1A1.nameInstanceAS inste, <br /> E1A1.nameClass AS classe, <br /> E1A1.value AS dx, <br /> E1A2.value AS dy, <br />
E1A3.valueAS dz, <br /> E1A4.value AS v, <br /> I0.value AS ix, <br /> I1.value AS iy, <br /> I2.value AS iz, <br />
I3.valueAS iv <br /> FROM <br /> instance_Attribute AS E1A1, <br /> instance_Attribute AS E1A2, <br />
instance_AttributeAS E1A3, <br /> instance_Attribute AS E1A4, <br /> Influence AS I0, <br /> Influence AS I1, <br />
InfluenceAS I2, <br /> Influence AS I3 <br /> WHERE<br /> E1A1.nameAttribute LIKE 'directionx' AND <br />
E1A2.nameInstanceLIKE E1A1.nameInstance  AND <br /> E1A2.nameClass LIKE E1A1.nameClass  AND <br /> E1A2.nameAttribute
LIKE'directiony' AND <br /> E1A3.nameInstance LIKE E1A1.nameInstance  AND <br /> E1A3.nameClass LIKE E1A1.nameClass 
AND<br /> E1A3.nameAttribute LIKE 'directionz' AND <br /> E1A4.nameInstance LIKE E1A1.nameInstance  AND <br />
E1A4.nameClassLIKE E1A1.nameClass  AND <br /> E1A4.nameAttribute LIKE 'vitesse' AND <br /> I0.nameClass LIKE
E1A1.nameClassAND <br /> I0.nameInstance LIKE E1A1.nameInstance AND <br /> I0.nameInfluence LIKE 'inf_directionx' AND
<br/> I1.nameClass LIKE E1A1.nameClass AND <br /> I1.nameInstance LIKE E1A1.nameInstance AND <br /> I1.nameInfluence
LIKE'inf_directiony' AND <br /> I2.nameClass LIKE E1A1.nameClass AND <br /> I2.nameInstance LIKE E1A1.nameInstance AND
<br/> I2.nameInfluence LIKE 'inf_directionz' AND <br /> I3.nameClass LIKE E1A1.nameClass AND <br /> I3.nameInstance
LIKEE1A1.nameInstance AND <br /> I3.nameInfluence LIKE 'inf_vitesse' ;<br /><p> Michel Soto<br />
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