Epic: FSST Array improvements

[AdamGS]

• WIP: FSSTView #4379
• WIP fsst+ #4132
• FSST::take depends on VarBin::take returning a VarBin #4757
• Can FSST be written into VarBinView instead of VarBin? #1987
• DuckDB related work tracked here: duckdb extension next steps #3332

[robert3005]

#4132 and #4379

[AdamGS]

added to the issue

[AdamGS]

(CC @a10y as you seem to be the main person pushing this work)

[a10y]

FSSTView is an attempt to implement #1987 via a new encoding that just wraps varbinview for the compressed data.

It leads to some tpch/clickbench speedups (mostly due to fast random ops on views) but at the expense of making files up to 20% larger due to the inlined views. In the worst case for columns with all inined strings, this results in no compression.

I get around this by ZSTD compressing the views, which works but then some of the performance benefits wash away and the files are still a bit bigger.

Generally it seems like views are suboptimal way to store FSST data at rest

[joseph-isaacs]

What about using ListView<u8> to store FSST compressed codes?