Avoid reading and decompressing index blocks during query planning

[joka921]

Avoid reading and decompressing the first and last block of an index scan during query planning (which requires only a size estimate and not the exact size). This added significant performance overhead, when only few blocks were eventually read in the index scan. Instead, we now do the following: First check whether the first and last block fully match the scan specification (this is fast). Second, if this is not the case, assume that the number of elements is a fixed fraction of total number of elements in the block (which we know from the metadata). The fixed fraction is defined by the new runtime parameter small-index-scan-size-estimate-divisor.

[sparql-conformance]

Conformance check passed ✅

No test result changes.

Details: https://qlever.cs.uni-freiburg.de/sparql-conformance-ui?cur=8b548d866c9004ca33be782ac61bdac04ebf1756&prev=acb6633debc7341985341aff147b5038cc8d951b

[codecov]

Codecov Report

Attention: Patch coverage is 93.87755% with 3 lines in your changes missing coverage. Please review.

Project coverage is 89.93%. Comparing base (acb6633) to head (dc689ea).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
src/index/CompressedRelation.cpp	93.47%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1725      +/-   ##
==========================================
+ Coverage   89.86%   89.93%   +0.06%     
==========================================
  Files         389      393       +4     
  Lines       37308    37611     +303     
  Branches     4204     4231      +27     
==========================================
+ Hits        33527    33824     +297     
- Misses       2485     2490       +5     
- Partials     1296     1297       +1     

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[hannahbast]

1-1 with Johannes, looks great, some minor improvements in clarity requested

[hannahbast]

Awesome!

[sonarqubecloud]

Quality Gate passed

Issues
5 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud