feat: Support PostgreSQL ^@ ("starts with"), and ~~,~~*,!~~,!~~* ("like", "ilike") string-matching operators

[alexander-beedie]

Adds support for the following PostgreSQL string matching operators ¹:

• ^@: "starts with"
• ~~: "like"
• ~~*: "ilike"
• !~~: "not like"
• !~~*: "not ilike"

Example

import polars as pl

df = pl.DataFrame({
    "x": ["aaa", "bbb", "a"],
    "y": ["abc", "b", "aa"],
})

df.sql("""
  SELECT
    x,
    x ^@ 'a' AS x_starts_with_a,
    x ~~* '%B' AS x_ends_with_b
  FROM self
""")
# shape: (3, 3)
# ┌─────┬─────────────────┬───────────────┐
# │ x   ┆ x_starts_with_a ┆ x_ends_with_b │
# │ --- ┆ ---             ┆ ---           │
# │ str ┆ bool            ┆ bool          │
# ╞═════╪═════════════════╪═══════════════╡
# │ aaa ┆ true            ┆ false         │
# │ bbb ┆ false           ┆ true          │
# │ a   ┆ true            ┆ false         │
# └─────┴─────────────────┴───────────────┘

df.sql("""
  SELECT
    x,
    y,
    x ^@ y AS x_starts_with_y
    x ~~ '%a' AS x_ends_with_a
  FROM self
""")
# shape: (3, 4)
# ┌─────┬─────┬─────────────────┬───────────────┐
# │ x   ┆ y   ┆ x_starts_with_y ┆ x_ends_with_a │
# │ --- ┆ --- ┆ ---             ┆ ---           │
# │ str ┆ str ┆ bool            ┆ bool          │
# ╞═════╪═════╪═════════════════╪═══════════════╡
# │ aaa ┆ abc ┆ false           ┆ true          │
# │ bbb ┆ b   ┆ true            ┆ false         │
# │ a   ┆ aa  ┆ false           ┆ true          │
# └─────┴─────┴─────────────────┴───────────────┘

Footnotes

1. https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE ↩

[codecov]

Codecov Report

Attention: Patch coverage is 95.45455% with 2 lines in your changes missing coverage. Please review.

Project coverage is 80.85%. Comparing base (4d2f928) to head (ca7aa57).
Report is 3 commits behind head on main.

Files	Patch %	Lines
crates/polars-sql/src/sql_expr.rs	95.45%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17251      +/-   ##
==========================================
+ Coverage   80.82%   80.85%   +0.02%     
==========================================
  Files        1466     1466              
  Lines      192313   192336      +23     
  Branches     2745     2745              
==========================================
+ Hits       155446   155509      +63     
+ Misses      36364    36324      -40     
  Partials      503      503              

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