What is the impact of having a confidential informant on a search warrant?

Nevertheless, reading the first sentence as the trial court did in deference to the magistrate's determination of probable cause and " 'the Fourth Amendment's strong preference for searches conducted pursuant to a warrant' " (Illinois v. Gates (1983) 462 U.S. 213, 236, 103 S.Ct. 2317, 2331, 76 L.Ed.2d 527), the sentence states only this: a confidential reliable informant was present at petitioners' residence within two days prior to preparation of the affidavit when heroin was sold from the residence. The remaining [199 Cal.App.3d 1463] information concerning the confidential informant is simply that he or she was at the residence on numerous occasions, for which no date or timeframe is specified, when heroin was sold from the residence. Presumably these are the occasions described in the affidavit when the informant accompanied unidentified individuals to the residence for the purpose of purchasing heroin, observed these individuals enter the residence and exit within a short period of time, immediately displaying to the informant a quantity of heroin which they told the informant had been purchased inside the residence. None of these unnamed individuals could identify or describe the person who purportedly sold them the heroin, nor could the confidential informant supply this fairly critical piece of information.