postgresql function not accepting null values in select statement

<div class="Section1"><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green">Hi,</span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green"> </span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green">If I pass null value as the parameter of postgresql function, which is used in the where clause of select
statementis not functioning properly.</span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS
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color:green"> </span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green">I have also changed the value of transform_null_equals = on in the conf file and restarted postgresql. But
itis still giving error. </span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green"> </span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green">Is there any possible solution.</span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS
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color:green"> </span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green">Thanks,</span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"MS Reference Sans
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color:green">Jyoti </span></div>