Optimize data retrieval for tables when no fields are accessed [CORE1598]

[firebird-automations]

Submitted by: @dyemanov

There are some queries (e.g. select count(*) from <tab>) that don't access any table fields (explicitly or implicitly). In this case, only the record header could be processed and the record data decompression could be avoided. Simple tests against the prototype implementation show about 50-80% of performance improvement (when appropriate data pages are cached).

[firebird-automations]

Modified by: @dyemanov

status: Open [ 1 ] => Resolved [ 5 ]

resolution: Fixed [ 1 ]

Fix Version: 2.5 Alpha 1 [ 10224 ]

[firebird-automations]

Modified by: @dyemanov

Target: 2.5.0 [ 10221 ]

[firebird-automations]

Modified by: @dyemanov

priority: Major [ 3 ] => Minor [ 4 ]

[firebird-automations]

Modified by: @pcisar

Workflow: jira [ 13430 ] => Firebird [ 14075 ]

[firebird-automations]

Modified by: @pcisar

status: Resolved [ 5 ] => Closed [ 6 ]

[firebird-automations]

Modified by: @pavel-zotov

QA Status: No test