feat: mp_rowhash macro and fixed failing tests

2026-07-23 23:45:28 +00:00 · 2026-07-18 13:09:58 +01:00
parent d489c98b87
commit 167defb31b
20 changed files with 458 additions and 53 deletions
@@ -0,0 +1,92 @@
+/**
+  @file
+  @brief Iterative row-level MD5 hash generator
+  @details Generates DATA step statements that compute a deterministic,
+    row-level MD5 hash using a Merkle-style construction.  Each variable is
+    hashed independently and the resulting raw 16-byte digests are combined
+    iteratively.  This avoids concatenating the per-variable hex digests into a
+    single SAS character expression, which overflows when datasets contain many
+    variables.
+
+    Temporary variables use five leading underscores.
+
+    This macro is called from inside a DATA step.  The caller is responsible
+    for declaring the output hash column if it does not already exist on the
+    input dataset.
+
+    Variables are hashed in the order supplied.  If a particular variable
+    needs to influence the hash first (for example the previous row hash in
+    `mp_hashdataset`, or business dates in Data Controller's bitemporal
+    loader) simply list it first in `cvars` or `nvars`.
+
+  @param [in] md5_col= Name of the output hash column.
+  @param [in] cvars= Space separated list of character variables to hash.
+  @param [in] nvars= Space separated list of numeric variables to hash.
+
+  @version 9.3M5
+  @author Allan Bowe
+**/
+
+%macro mp_rowhash(
+    md5_col=
+    ,cvars=
+    ,nvars=
+  );
+
+  /* DATA step temp variables use five leading underscores.  The names
+      are generated at macro invocation to avoid clashing with data columns. */
+  %local state digest pair numtext normal i chars nums;
+  %let state=%mf_getuniquename(prefix=_____state_);
+  %let digest=%mf_getuniquename(prefix=_____digest_);
+  %let pair=%mf_getuniquename(prefix=_____pair_);
+  %let numtext=%mf_getuniquename(prefix=_____numtext_);
+  %let normal=%mf_getuniquename(prefix=_____normal_);
+  %let i=%mf_getuniquename(prefix=_____i_);
+  %let chars=%mf_getuniquename(prefix=_____chars_);
+  %let nums=%mf_getuniquename(prefix=_____nums_);
+
+  length &state $16
+        &digest $16
+        &pair $32
+        &numtext $64
+        &normal &i 8;
+  if _n_=1 then call missing(&state,&digest,&pair,&numtext,&normal,&i);
+  drop &state &digest &pair &numtext &normal &i;
+
+  /* Versioned seed prevents confusion with other hashing schemes. */
+  &state = md5('DC HASH v2');
+
+  %if %length(&cvars)>0 %then %do;
+    array &chars{*} $ &cvars;
+    do &i = 1 to dim(&chars);
+      /* Leading blanks are retained. */
+      &digest = md5(trimn(&chars[&i]));
+      substr(&pair,  1, 16) = &state;
+      substr(&pair, 17, 16) = &digest;
+      &state = md5(&pair);
+    end;
+  %end;
+
+  %if %length(&nvars)>0 %then %do;
+    array &nums{*} &nvars;
+    do &i = 1 to dim(&nums);
+      /*
+        multiply-by-one for consistent cross-system precision.
+        Ignore null to protect SAS special missing values.
+      */
+      &normal = ifn(
+        missing(&nums[&i]),
+        &nums[&i],
+        &nums[&i] * 1
+      );
+      &numtext = put(&normal, binary64.);
+      &digest = md5(trim(&numtext));
+      substr(&pair,  1, 16) = &state;
+      substr(&pair, 17, 16) = &digest;
+      &state = md5(&pair);
+    end;
+  %end;
+
+  &md5_col = put(&state, $hex32.);
+
+%mend mp_rowhash;