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authorTomas Vondra <tomas.vondra@postgresql.org>2022-01-12 19:59:30 +0100
committerTomas Vondra <tomas.vondra@postgresql.org>2022-01-12 22:27:24 +0100
commit6b94e7a6da2f1c6df1a42efe64251f32a444d174 (patch)
tree787346c6c0e4c4cb9997076b8d9da7380823dd8c /src/backend/optimizer/path/joinpath.c
parent025b920a3d45fed441a0a58fdcdf05b321b1eead (diff)
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Consider fractional paths in generate_orderedappend_paths
When building append paths, we've been looking only at startup and total costs for the paths. When building fractional paths that may eliminate the cheapest one, because it may be dominated by two separate paths (one for startup, one for total cost). This extends generate_orderedappend_paths() to also consider which paths have lowest fractional cost. Currently we only consider paths matching pathkeys - in the future this may be improved by also considering paths that are only partially sorted, with an incremental sort on top. Original report of an issue by Arne Roland, patch by me (based on a suggestion by Tom Lane). Reviewed-by: Arne Roland, Zhihong Yu Discussion: https://postgr.es/m/e8f9ec90-546d-e948-acce-0525f3e92773%40enterprisedb.com Discussion: https://postgr.es/m/1581042da8044e71ada2d6e3a51bf7bb%40index.de
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