PAX: treat PAX tables as AO-like in index path generation#1761
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Random TID fetches on PAX tables re-decompress entire stripes (1.5 MB ZSTD blocks) per tuple and bypass the buffer pool, just like AO/AOCS. get_index_paths() already routes AO/AOCS relations to Bitmap paths only and skips IndexScan/IndexOnlyScan (the latter is unimplemented for AO). Extend the same treatment to PAX so that a btree index over a PAX table no longer triggers full-table Index Only Scan when enable_seqscan=off, which previously caused customer queries to hang indefinitely. Detection uses the existing PAX_AM_OID; RelOptInfo gains a relam field cached from rd_rel->relam (mirroring amhandler) so the planner can do the comparison without opening the relation. Heap tables and existing AO behavior are unaffected.
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Random TID fetches on PAX tables re-decompress entire stripes (1.5 MB ZSTD blocks) per tuple and bypass the buffer pool, just like AO/AOCS. get_index_paths() already routes AO/AOCS relations to Bitmap paths only and skips IndexScan/IndexOnlyScan (the latter is unimplemented for AO). Extend the same treatment to PAX so that a btree index over a PAX table no longer triggers full-table Index Only Scan when enable_seqscan=off, which previously caused customer queries to hang indefinitely.
Detection uses the existing PAX_AM_OID; RelOptInfo gains a relam field cached from rd_rel->relam (mirroring amhandler) so the planner can do the comparison without opening the relation.
Heap tables and existing AO behavior are unaffected.
Fixes #ISSUE_Number
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make installcheckmake -C src/test installcheck-cbdb-parallelImpact
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