Final Commit for to implement Functional Dependency in PostgreSQL

README

@@ -25,3 +25,14 @@ instructions.
 The latest version of this software may be obtained at
 https://www.postgresql.org/download/.  For more information look at our
 web site located at https://www.postgresql.org/.
+
+Following Files have been ammended to include functional dependency in PostgreSQL.
+
+src/backend/access/nbtree/nbtinsert.c
+src/backend/access/nbtree/nbtsearch.c
+src/backend/access/nbtree/nbtutils.c
+src/backend/catalog/index.c
+src/backend/tcop/postgres.c
+src/include/access/nbtree.h
+
+install/data/gdata.h

gdata.h

+/* CS631 Start */
+/*
+ * gdata.h
+ *
+ *  Created on: 28-Nov-2022
+ *      Author: abuhujair
+ */
+
+extern int fd_flag;
+int check_fd(int id_num);
+
+#ifndef INSTALL_DATA_GDATA_H_
+#define INSTALL_DATA_GDATA_H_
+#endif /* INSTALL_DATA_GDATA_H_ */
+/* CS631 End */

idx_inf.txt

+32789
+40981
+40982
+40986
+40987
+40991
+49176
+49183
+49184

src/backend/access/nbtree/nbtinsert.c

@@ -26,6 +26,8 @@
 #include "storage/smgr.h"
 
 /* CS631 Start */
+/* The file at /install/data/gdata.h/
+ * */
 #include "/home/abuhujair/git/postgresql/install/data/gdata.h"
 /* CS631 End */
 
@@ -111,9 +113,10 @@ _bt_doinsert(Relation rel, IndexTuple itup,
 	bool		checkingunique = (checkUnique != UNIQUE_CHECK_NO);
 
 	/* CS631 Start */
-	// Oid 		special = 32788;
+	/* We are creating a flag to implement FD functionality.
+	 * FD implementation is being done in line with what postgres implements to do uniqueness check.
+	 * */
 	bool		checkingfd = false;
-	// if ( rel->rd_index->indexrelid == special )
 	if ( check_fd( (int)rel->rd_index->indexrelid ) )
 		checkingfd = true;
 	/* CS631 End */
@@ -212,6 +215,9 @@ search:
 	 */
 
 	/* CS631 Start */
+	/* We will enter the _bt_check_unique function in case
+	 * while checking for FD as well as to check uniqueness.
+	 * */
 	if (checkingunique || checkingfd)
 	/* CS631 End */
 	{
@@ -436,9 +442,10 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 	int			curposti = 0;
 
 	/* CS631 Start */
-	// Oid 		special = 32788;
+	/* We are again checking if the given index defines any FD constraints.
+	 * and raising the flag.
+	 * */
 	bool		checkfd = false;
-	//if ( rel->rd_index->indexrelid == special )
 	if ( check_fd((int)rel->rd_index->indexrelid) )
 		checkfd = true;
 	/* CS631 End */
@@ -679,6 +686,8 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 					insertstate->bounds_valid = false;
 
 					/* CS631 Start */
+					/* depending on whether the checkUnique flag was turned on,
+					 * or checkfd we will decide which error message to be displayed */
 					if ( checkUnique )
 					{
 						Datum		values[INDEX_MAX_KEYS];

src/backend/access/nbtree/nbtsearch.c

@@ -756,7 +756,14 @@ _bt_compare(Relation rel,
 	}
 
 	/* CS631 Start */
-	// if (rel->rd_index->indexrelid == special)
+	/* The _bt_compare function implements tiebreaker in case of primary/unique key
+	 * as non-pivot search, which imply it will return the offset the first index tuple
+	 * it matches with, while for non-primary key it returns the offset of one more
+	 * than last tuple which is equal to key.
+	 * For checking FD constraint, we need to verify with first element in the tree.
+	 * So instead of breaking tie using some other factor in case of FD index,
+	 *  we return 0, indicating we found a match.
+	 * */
 	if ( check_fd((int)rel->rd_index->indexrelid) )
 		return 0;
 	/* CS631 End */
@@ -2514,14 +2521,19 @@ _bt_initialize_more_data(BTScanOpaque so, ScanDirection dir)
 /* CS631 Start */
 
 /*----------
- * _bt_compare_fd() -- Compare insertion-type scankey to tuple on a page.
+ * _bt_compare_fd() -- Compare the inserting tuple with that of tuple in the tree.
  *
  * page/offnum: location of btree item to be compared to.
  *
- * This routine returns:
- * <0 if scankey < tuple at offnum;
- * 0 if scankey == tuple at offnum;
- * >0 if scankey > tuple at offnum.
+ *
+ * For A->B FD constraints this routine returns:
+ * 	A			B			Return Value
+ *  Equal		Equal		1
+ *  Unequal		Equal		1
+ *  Equal		Unequal		0
+ *  Unequal		Unequal		1
+ *
+ * Here A is represented by key of the index, and B is the Covering attribute of the index.
  *
  * NULLs in the keys are treated as sortable values.  Therefore
  * "equality" does not necessarily mean that the item should be returned
@@ -2550,13 +2562,10 @@ _bt_compare_fd(Relation rel,
 	TupleDesc itupdesc = RelationGetDescr(rel);
 	BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 	IndexTuple itup;
-	// ItemPointer heapTid;
 	ScanKey scankey;
 	int ncmpkey;
 	int ntupatts;
 	int32 result;
-	// BTScanInsert nonkey;
-	// ScanKey scannonkey;
 
 	Assert(_bt_check_natts(rel, key->heapkeyspace, page, offnum));
 	Assert(key->keysz <= IndexRelationGetNumberOfKeyAttributes(rel));
@@ -2584,6 +2593,10 @@ _bt_compare_fd(Relation rel,
 	* _bt_first).
 	*/
 
+	/* Here we are only checking the key attributes of the index,
+	 * which is similar to the one in _bt_compare. Here we have ommitted, tie breakers
+	 * we are just checking for equality.
+	 * */
 	ncmpkey = Min(ntupatts, key->keysz);
 	Assert(key->heapkeyspace || ncmpkey == key->keysz);
 	Assert(!BTreeTupleIsPosting(itup) || key->allequalimage);
@@ -2615,8 +2628,12 @@ _bt_compare_fd(Relation rel,
 		scankey++;
 	}
 
-	// nonkey = _bt_mkscankey_nonkey(rel, itup_);
-	// scannonkey = nonkey->scankeys;
+	/* This part check for inequality in B and is checked only if A is unequal.
+	 * We are essentially comparing all the attributes of covering index
+	 * using the sk_func of the first attribute of A. Hence, this became our
+	 * constraints while implementing FD. All the attributes of B, need to be of same
+	 * datatype as first attribute of A.
+	 * */
 	scankey = key->scankeys;
 	for (int i = ncmpkey+1; i <= ntupatts; i++)
 	{
@@ -2637,7 +2654,6 @@ _bt_compare_fd(Relation rel,
 			result = 0;
 			return result;
 			}
-		scankey++;
 	}
 
 	if (result == 0){
@@ -2647,4 +2663,3 @@ _bt_compare_fd(Relation rel,
 }
 
 /* CS631 End */
-

src/backend/access/nbtree/nbtutils.c

@@ -2752,33 +2752,14 @@ _bt_allequalimage(Relation rel, bool debugmessage)
 
 /* CS631 Start */
 /*
- * _bt_mkscankey
- *		Build an insertion scan key that contains comparison data from itup
- *		as well as comparator routines appropriate to the key datatypes.
- *
- *		When itup is a non-pivot tuple, the returned insertion scan key is
- *		suitable for finding a place for it to go on the leaf level.  Pivot
- *		tuples can be used to re-find leaf page with matching high key, but
- *		then caller needs to set scan key's pivotsearch field to true.  This
- *		allows caller to search for a leaf page with a matching high key,
- *		which is usually to the left of the first leaf page a non-pivot match
- *		might appear on.
- *
- *		The result is intended for use with _bt_compare() and _bt_truncate().
- *		Callers that don't need to fill out the insertion scankey arguments
- *		(e.g. they use an ad-hoc comparison routine, or only need a scankey
- *		for _bt_truncate()) can pass a NULL index tuple.  The scankey will
- *		be initialized as if an "all truncated" pivot tuple was passed
- *		instead.
- *
- *		Note that we may occasionally have to share lock the metapage to
- *		determine whether or not the keys in the index are expected to be
- *		unique (i.e. if this is a "heapkeyspace" index).  We assume a
- *		heapkeyspace index when caller passes a NULL tuple, allowing index
- *		build callers to avoid accessing the non-existent metapage.  We
- *		also assume that the index is _not_ allequalimage when a NULL tuple
- *		is passed; CREATE INDEX callers call _bt_allequalimage() to set the
- *		field themselves.
+ * _bt_mkscankey_nonkey
+ *		Build a scan key that contains comparison data from itup
+ *		as well as comparator routines appropriate to the datatypes.
+ *
+ *		The result is intended for use with _bt_compare_fd(). But did, not workout,
+ *		as index relation data does not store information about comparator routines
+ *		for nonkey attributes. Hence the function is not being used. Other functionality
+ *		of the function is similar to the _bt_mkscankey.
  */
 BTScanInsert
 _bt_mkscankey_nonkey(Relation rel, IndexTuple itup)
@@ -2822,7 +2803,6 @@ _bt_mkscankey_nonkey(Relation rel, IndexTuple itup)
 	skey = key->scankeys;
 	for (i = indnkeyatts; i < tupnatts; i++)
 	{
-		// FmgrInfo   *procinfo;
 		RegProcedure procedure;
 		Datum		arg;
 		bool		null;
@@ -2832,7 +2812,6 @@ _bt_mkscankey_nonkey(Relation rel, IndexTuple itup)
 		 * We can use the cached (default) support procs since no cross-type
 		 * comparison can be needed.
 		 */
-		// procinfo = index_getprocinfo(rel, i + 1, BTORDER_PROC);
 		procedure = index_getprocid(rel, i + 1, BTORDER_PROC);
 
 

src/backend/catalog/index.c

@@ -86,13 +86,11 @@
 #include "utils/tuplesort.h"
 
 /* CS631 Start */
-# include <string.h>
-# include <stdio.h>
+#include <string.h>
+#include <stdio.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <limits.h>
-
-// #include "../../../install/data/gdata.h"
 #include "/home/abuhujair/git/postgresql/install/data/gdata.h"
 /* CS631 End */
 
@@ -537,6 +535,9 @@ AppendAttributeTuples(Relation indexRelation, Datum *attopts)
 }
 
 /* CS631 Start */
+/* This function adds an entry of relation id of the index to the file inx_inf.txt if
+ * user wants to implements index as an FD
+ * */
 int add_entry(char *idxid)
 {
 
@@ -682,6 +683,8 @@ UpdateIndexRelation(Oid indexoid,
 	heap_freetuple(tuple);
 
 	/* CS631 Start */
+	/* If the given index is created successfully, and if the index is created
+	 * to implement FD constraints we will add it.*/
 	if(fd_flag)
 	{
 		char idxid[20];

src/backend/tcop/postgres.c

@@ -946,6 +946,9 @@ pg_plan_queries(List *querytrees, const char *query_string, int cursorOptions,
 }
 
 /* CS631 Start */
+/* We have not ammended the parser to parse the SQL query to create FD, instead
+ * just changing the "FD" to "INDEX" and "determines" to "include" we are creating FD.
+ * */
 char* replaceWord(const char* s, const char* oldW,
                 const char* newW)
 {
@@ -974,8 +977,14 @@ char* replaceWord(const char* s, const char* oldW,
 }
 
 #include "../../../install/data/gdata.h"
+/* This flag is being used to indicate whether the query is create FD.*/
 int fd_flag=0;
 
+/* This function is being called whenver we want to check if the given index relation
+ * ID is an FD.
+ * Since we have saved the index which implements the FD constraints in file, this just
+ * searches the index in the file.
+ * */
 int check_fd(int id_num)
 {
 	FILE * fp;
@@ -1014,6 +1023,8 @@ exec_simple_query(const char *query_string)
 	char		msec_str[32];
 
 	/* CS631 Start */
+	/* If the given SQL query is to create FD, this will create and equivalent query to create the index
+	 *  and raise the fd_flag*/
 	fd_flag=0;
 	if (strstr(query_string, "FD") && strstr(query_string, "determines")) {
 		const char old[]="FD";