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d3eaab3ef0
My expanded-objects patch (commit 1dc5ebc9077ab742) included code to make plpgsql pass expanded-object variables as R/W pointers to certain functions that are trusted for modifying such variables in-place. However, that optimization got broken by commit 6c82d8d1fdb1f126, which arranged to share a single ParamListInfo across most expressions evaluated by a plpgsql function. We don't want a R/W pointer to be passed to other functions just because we decided one function was safe! Fortunately, the breakage was in the other direction, of never passing a R/W pointer at all, because we'd always have pre-initialized the shared array slot with a R/O pointer. So it was still functionally correct, but we were back to O(N^2) performance for repeated use of "a := a || x". To fix, force an unshared param array to be used when the R/W param optimization is active. Commit 6c82d8d1fdb1f126 is in HEAD only, so no need for a back-patch.