I experienced both within the same company - they started without code reviews, and the later introduced them. The result was overwhelmingly positive, greatly improving code quality and helping spread knowledge of new systems and utilities.
I certainly believe it's possible to do code reviews sufficiently "wrong" that they're a net hindrance. Drape them in too much ceremony, put too much emphasis on style (Bob doesn't like your whitespace preferences, and he's the code owner, so your changelist is vetoed!) and too little emphasis on subsistence (these corner cases and possible bugs concern me).
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We went with a relatively light touch approach. Nothing was technologically enforced - our lead dev simply told us he wanted everyone to start having everything reviewed by anyone - both for code quality and to spread knowledge - and that he'd be pissed if he found a bug in one of our changelists and found out it hadn't been reviewed, going forward.
Whitespace / naming stuff I tended to submit without review.
Quick and obvious fixes, small changes, etc., I was fairly willing to start a review request, submit, and then fix anything caught in the review in a followup changelist.
For larger changes where I had more reservations, I'd usually hold off on submitting until after a review. Maybe threaten to submit if they were dragging their feet too long :P
I certainly believe it's possible to do code reviews sufficiently "wrong" that they're a net hindrance. Drape them in too much ceremony, put too much emphasis on style (Bob doesn't like your whitespace preferences, and he's the code owner, so your changelist is vetoed!) and too little emphasis on subsistence (these corner cases and possible bugs concern me).
.
We went with a relatively light touch approach. Nothing was technologically enforced - our lead dev simply told us he wanted everyone to start having everything reviewed by anyone - both for code quality and to spread knowledge - and that he'd be pissed if he found a bug in one of our changelists and found out it hadn't been reviewed, going forward.
Whitespace / naming stuff I tended to submit without review.
Quick and obvious fixes, small changes, etc., I was fairly willing to start a review request, submit, and then fix anything caught in the review in a followup changelist.
For larger changes where I had more reservations, I'd usually hold off on submitting until after a review. Maybe threaten to submit if they were dragging their feet too long :P