Currently there is no way to backup 'pg_statistic' because columns of 'anyarray' type cannot be reconstructed solely with their textual representation. Meanwhile, all that is needed to solve this problem is a small extension capable of retrieving the element type of an 'anyarray' object and recreating this particular 'anyarray' object using the 'array_in' procedure.
Please submit a patch on core for this.
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Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services