Re: [HACKERS] pgbench more operators & functions

Hello Pavel,

Here is a v13. No code changes, but TAP tests added to maintain pgbench 
coverage to green.


Summary of patch contents:

This patch extends pgbench expressions syntax while keeping 
compatibility with SQL expressions.

It adds support for NULL and BOOLEAN, as well as assorted logical, 
comparison and test operators (AND, <>, <=, IS NULL...).

A CASE construct is provided which takes advantage of the added BOOLEAN.

Integer and double functions and operators are also extended: bitwise 
operators (<< & ...), exp/ln, mod() as synonymous to % (matching pg).

Added TAP tests maintain pgbench source coverage to green (if you ignore 
lexer & parser generated files...).


Future plans include extending and synchronizing psql & pgbench variable 
and expression syntaxes:
  - move expression parsing and evaluation in fe_utils,
    which would allow to
  - extend psql with some \let i <expression> cliend-side syntax
    (ISTM that extending the \set syntax cannot be upward compatible)
    and probably handle \let as a synonymous to \set in pgbench.
  - allow \if <expression> in psql instead of just \if <boolean>
  - add \if ... support to pgbench
  - maybe add TEXT type support to the expression engine, if useful
  - maybe add :'var" and :"var" support to pgbench, if useful

There are already patches in the queue for:
  - testing whether a variable is defined in psql
    feature could eventually be added to pgbench as well
  - adding \gset (& \cset) to pgbench to get output of possibly
    combined queries into variables, which can be used for making
    decisions later in the script.

-- 
Fabien.
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