public virtual Expression Translate(MethodCallExpression methodCallExpression)
{
if (!methodCallExpression.Method.Equals(_methodInfo))
{
return(null);
}
var argument0 = methodCallExpression.Arguments[0];
// If Contains() is being invoked on a citext, ensure that the string argument is explicitly cast into a
// citext (instead of the default text for a CLR string) as otherwise PostgreSQL prefers the text variant of
// the ambiguous call STRPOS(citext, text) and the search will be case-sensitive. See #384.
if (argument0 != null &&
methodCallExpression.Object?.FindProperty(typeof(string))?.GetConfiguredColumnType() == "citext")
{
argument0 = new ExplicitStoreTypeCastExpression(argument0, typeof(string), "citext");
}
return(Expression.GreaterThan(
new SqlFunctionExpression("STRPOS", typeof(int), new[]
{
methodCallExpression.Object,
argument0
}),
Expression.Constant(0)
));
}
public virtual Expression Translate(MethodCallExpression e)
{
if (!e.Method.Equals(_methodInfo) || e.Object == null)
{
return(null);
}
var constantPatternExpr = e.Arguments[0] as ConstantExpression;
if (constantPatternExpr != null)
{
// The pattern is constant. Escape all special characters (%, _, \) in C# and send
// a simple LIKE
return(new LikeExpression(
e.Object,
Expression.Constant(Regex.Replace((string)constantPatternExpr.Value, @"([%_\\])", @"\$1") + '%')
));
}
// The pattern isn't a constant (i.e. parameter, database column...).
// First run LIKE against the *unescaped* pattern (which will efficiently use indices),
// but then add another test to filter out false positives.
var pattern = e.Arguments[0];
Expression leftExpr = new SqlFunctionExpression("LEFT", typeof(string), new[]
{
e.Object,
new SqlFunctionExpression("LENGTH", typeof(int), new[] { pattern }),
});
// If StartsWith is being invoked on a citext, the LEFT() function above will return a reglar text
// and the comparison will be case-sensitive. So we need to explicitly cast LEFT()'s return type
// to citext. See #319.
if (e.Object.FindProperty(typeof(string))?.GetConfiguredColumnType() == "citext")
{
leftExpr = new ExplicitStoreTypeCastExpression(leftExpr, typeof(string), "citext");
}
return(Expression.AndAlso(
new LikeExpression(e.Object, Expression.Add(pattern, Expression.Constant("%"), _concat)),
Expression.Equal(
leftExpr,
pattern
)
));
}
