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feat: support TOP operator #756

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dlawin merged 4 commits into from
Nov 13, 2023
Merged

feat: support TOP operator #756

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94b6d93
feat: support TOP operator
pik94 Oct 28, 2023
0665452
feat: use a separate render function for limited query
pik94 Nov 8, 2023
0bd24a3
feat: update tests
pik94 Nov 8, 2023
6da7db7
Merge branch 'master' into support-top-operator
dlawin Nov 13, 2023
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8 changes: 6 additions & 2 deletions data_diff/databases/base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -202,6 +202,7 @@ class BaseDialect(abc.ABC):
TYPE_CLASSES: ClassVar[Dict[str, Type[ColType]]] = {}

PLACEHOLDER_TABLE = None # Used for Oracle
USE_TOP_INSTEAD_LIMIT: bool = False # True for MsSQL or Teradata

def parse_table_name(self, name: str) -> DbPath:
"Parse the given table name into a DbPath"
Expand Down Expand Up @@ -471,7 +472,10 @@ def render_select(self, parent_c: Compiler, elem: Select) -> str:
columns = ", ".join(map(compile_fn, elem.columns)) if elem.columns else "*"
distinct = "DISTINCT " if elem.distinct else ""
optimizer_hints = self.optimizer_hints(elem.optimizer_hints) if elem.optimizer_hints else ""
select = f"SELECT {optimizer_hints}{distinct}{columns}"
if elem.limit_expr is not None and self.USE_TOP_INSTEAD_LIMIT:
select = f"SELECT TOP {elem.limit_expr} {optimizer_hints}{distinct}{columns}"
else:
select = f"SELECT {optimizer_hints}{distinct}{columns}"

if elem.table:
select += " FROM " + self.compile(c, elem.table)
Expand All @@ -491,7 +495,7 @@ def render_select(self, parent_c: Compiler, elem: Select) -> str:
if elem.order_by_exprs:
select += " ORDER BY " + ", ".join(map(compile_fn, elem.order_by_exprs))

if elem.limit_expr is not None:
if elem.limit_expr is not None and not self.USE_TOP_INSTEAD_LIMIT:
has_order_by = bool(elem.order_by_exprs)
select += " " + self.offset_limit(0, elem.limit_expr, has_order_by=has_order_by)

Expand Down