Added a test

tests/queries/0_stateless/01250_fixed_string_comparison.reference

@@ -0,0 +1,110 @@
+Row 1:
+──────
+equals(b, b):    1
+greater(b, b):   0
+less(b, b):      0
+equals(b, c):    0
+greater(b, c):   0
+less(b, c):      1
+equals(b, d):    0
+greater(b, d):   0
+less(b, d):      1
+equals(b, bf):   1
+greater(b, bf):  0
+less(b, bf):     0
+equals(b, cf):   0
+greater(b, cf):  0
+less(b, cf):     1
+equals(b, df):   0
+greater(b, df):  0
+less(b, df):     1
+equals(c, b):    0
+greater(c, b):   1
+less(c, b):      0
+equals(c, c):    1
+greater(c, c):   0
+less(c, c):      0
+equals(c, d):    0
+greater(c, d):   0
+less(c, d):      1
+equals(c, bf):   0
+greater(c, bf):  1
+less(c, bf):     0
+equals(c, cf):   1
+greater(c, cf):  0
+less(c, cf):     0
+equals(c, df):   0
+greater(c, df):  0
+less(c, df):     1
+equals(d, b):    0
+greater(d, b):   1
+less(d, b):      0
+equals(d, c):    0
+greater(d, c):   1
+less(d, c):      0
+equals(d, d):    1
+greater(d, d):   0
+less(d, d):      0
+equals(d, bf):   0
+greater(d, bf):  1
+less(d, bf):     0
+equals(d, cf):   0
+greater(d, cf):  1
+less(d, cf):     0
+equals(d, df):   1
+greater(d, df):  0
+less(d, df):     0
+equals(bf, b):   1
+greater(bf, b):  0
+less(bf, b):     0
+equals(bf, c):   0
+greater(bf, c):  0
+less(bf, c):     1
+equals(bf, d):   0
+greater(bf, d):  0
+less(bf, d):     1
+equals(bf, bf):  1
+greater(bf, bf): 0
+less(bf, bf):    0
+equals(bf, cf):  0
+greater(bf, cf): 0
+less(bf, cf):    1
+equals(bf, df):  0
+greater(bf, df): 0
+less(bf, df):    1
+equals(cf, b):   0
+greater(cf, b):  1
+less(cf, b):     0
+equals(cf, c):   1
+greater(cf, c):  0
+less(cf, c):     0
+equals(cf, d):   0
+greater(cf, d):  0
+less(cf, d):     1
+equals(cf, bf):  0
+greater(cf, bf): 1
+less(cf, bf):    0
+equals(cf, cf):  1
+greater(cf, cf): 0
+less(cf, cf):    0
+equals(cf, df):  0
+greater(cf, df): 0
+less(cf, df):    1
+equals(df, b):   0
+greater(df, b):  1
+less(df, b):     0
+equals(df, c):   0
+greater(df, c):  1
+less(df, c):     0
+equals(df, d):   1
+greater(df, d):  0
+less(df, d):     0
+equals(df, bf):  0
+greater(df, bf): 1
+less(df, bf):    0
+equals(df, cf):  0
+greater(df, cf): 1
+less(df, cf):    0
+equals(df, df):  1
+greater(df, df): 0
+less(df, df):    0

tests/queries/0_stateless/01250_fixed_string_comparison.sql

@@ -0,0 +1,45 @@
+WITH 'abb' AS b, 'abc' AS c, 'abd' AS d, toFixedString(b, 5) AS bf, toFixedString(c, 5) AS cf, toFixedString(d, 5) AS df
+SELECT 
+    b = b, b > b, b < b,
+    b = c, b > c, b < c,
+    b = d, b > d, b < d,
+    b = bf, b > bf, b < bf,
+    b = cf, b > cf, b < cf,
+    b = df, b > df, b < df,
+
+    c = b, c > b, c < b,
+    c = c, c > c, c < c,
+    c = d, c > d, c < d,
+    c = bf, c > bf, c < bf,
+    c = cf, c > cf, c < cf,
+    c = df, c > df, c < df,
+
+    d = b, d > b, d < b,
+    d = c, d > c, d < c,
+    d = d, d > d, d < d,
+    d = bf, d > bf, d < bf,
+    d = cf, d > cf, d < cf,
+    d = df, d > df, d < df,
+
+    bf = b, bf > b, bf < b,
+    bf = c, bf > c, bf < c,
+    bf = d, bf > d, bf < d,
+    bf = bf, bf > bf, bf < bf,
+    bf = cf, bf > cf, bf < cf,
+    bf = df, bf > df, bf < df,
+
+    cf = b, cf > b, cf < b,
+    cf = c, cf > c, cf < c,
+    cf = d, cf > d, cf < d,
+    cf = bf, cf > bf, cf < bf,
+    cf = cf, cf > cf, cf < cf,
+    cf = df, cf > df, cf < df,
+
+    df = b, df > b, df < b,
+    df = c, df > c, df < c,
+    df = d, df > d, df < d,
+    df = bf, df > bf, df < bf,
+    df = cf, df > cf, df < cf,
+    df = df, df > df, df < df
+
+FORMAT Vertical;