Be more consistent about errors for opfamily member lookup failures.

Add error checks in some places that were calling get_opfamily_member
or get_opfamily_proc and just assuming that the call could never fail.
Also, standardize the wording for such errors in some other places.

None of these errors are expected in normal use, hence they're just
elog not ereport.  But they may be handy for diagnosing omissions in
custom opclasses.

Rushabh Lathia found the oversight in RelationBuildPartitionKey();
I found the others by grepping for all callers of these functions.

Discussion: https://postgr.es/m/CAGPqQf2R9Nk8htpv0FFi+FP776EwMyGuORpc9zYkZKC8sFQE3g@mail.gmail.com

src/backend/catalog/index.c

@@ -1738,6 +1738,10 @@ BuildSpeculativeIndexInfo(Relation index, IndexInfo *ii)
 								index->rd_opcintype[i],
 								index->rd_opcintype[i],
 								ii->ii_UniqueStrats[i]);
+		if (!OidIsValid(ii->ii_UniqueOps[i]))
+			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
+				 ii->ii_UniqueStrats[i], index->rd_opcintype[i],
+				 index->rd_opcintype[i], index->rd_opfamily[i]);
 		ii->ii_UniqueProcs[i] = get_opcode(ii->ii_UniqueOps[i]);
 	}
 }

src/backend/catalog/partition.c

@@ -1187,14 +1187,15 @@ get_partition_operator(PartitionKey key, int col, StrategyNumber strategy,
 									  key->partopcintype[col],
 									  key->partopcintype[col],
 									  strategy);
+		if (!OidIsValid(operoid))
+			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
+				 strategy, key->partopcintype[col], key->partopcintype[col],
+				 key->partopfamily[col]);
 		*need_relabel = true;
 	}
 	else
 		*need_relabel = false;
 
-	if (!OidIsValid(operoid))
-		elog(ERROR, "could not find operator for partitioning");
-
 	return operoid;
 }
 

src/backend/executor/execExpr.c

@@ -1640,6 +1640,9 @@ ExecInitExprRec(Expr *node, PlanState *parent, ExprState *state,
 											 lefttype,
 											 righttype,
 											 BTORDER_PROC);
+					if (!OidIsValid(proc))
+						elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
+							 BTORDER_PROC, lefttype, righttype, opfamily);
 
 					/* Set up the primary fmgr lookup information */
 					finfo = palloc0(sizeof(FmgrInfo));

src/backend/executor/execReplication.c

@@ -81,9 +81,8 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 		operator = get_opfamily_member(opfamily, optype,
 									   optype,
 									   BTEqualStrategyNumber);
-
 		if (!OidIsValid(operator))
-			elog(ERROR, "could not find member %d(%u,%u) of opfamily %u",
+			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
 				 BTEqualStrategyNumber, optype, optype, opfamily);
 
 		regop = get_opcode(operator);

src/backend/executor/nodeIndexscan.c

@@ -1367,6 +1367,9 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index,
 											 op_lefttype,
 											 op_righttype,
 											 BTORDER_PROC);
+				if (!RegProcedureIsValid(opfuncid))
+					elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
+						 BTORDER_PROC, op_lefttype, op_righttype, opfamily);
 
 				inputcollation = lfirst_oid(collids_cell);
 				collids_cell = lnext(collids_cell);

src/backend/optimizer/path/indxpath.c

@@ -3978,13 +3978,13 @@ adjust_rowcompare_for_index(RowCompareExpr *clause,
 			expr_op = get_opfamily_member(opfam, lefttype, righttype,
 										  op_strategy);
 			if (!OidIsValid(expr_op))	/* should not happen */
-				elog(ERROR, "could not find member %d(%u,%u) of opfamily %u",
+				elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
 					 op_strategy, lefttype, righttype, opfam);
 			if (!var_on_left)
 			{
 				expr_op = get_commutator(expr_op);
 				if (!OidIsValid(expr_op))	/* should not happen */
-					elog(ERROR, "could not find commutator of member %d(%u,%u) of opfamily %u",
+					elog(ERROR, "could not find commutator of operator %d(%u,%u) of opfamily %u",
 						 op_strategy, lefttype, righttype, opfam);
 			}
 			new_ops = lappend_oid(new_ops, expr_op);

src/backend/optimizer/path/pathkeys.c

@@ -197,8 +197,8 @@ make_pathkey_from_sortinfo(PlannerInfo *root,
 									  opcintype,
 									  BTEqualStrategyNumber);
 	if (!OidIsValid(equality_op))	/* shouldn't happen */
-		elog(ERROR, "could not find equality operator for opfamily %u",
-			 opfamily);
+		elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
+			 BTEqualStrategyNumber, opcintype, opcintype, opfamily);
 	opfamilies = get_mergejoin_opfamilies(equality_op);
 	if (!opfamilies)			/* certainly should find some */
 		elog(ERROR, "could not find opfamilies for equality operator %u",

src/backend/optimizer/plan/createplan.c

@@ -2634,7 +2634,8 @@ create_indexscan_plan(PlannerInfo *root,
 										 exprtype,
 										 pathkey->pk_strategy);
 			if (!OidIsValid(sortop))
-				elog(ERROR, "failed to find sort operator for ORDER BY expression");
+				elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
+					 pathkey->pk_strategy, exprtype, exprtype, pathkey->pk_opfamily);
 			indexorderbyops = lappend_oid(indexorderbyops, sortop);
 		}
 	}
@@ -5738,7 +5739,7 @@ prepare_sort_from_pathkeys(Plan *lefttree, List *pathkeys,
 									 pk_datatype,
 									 pathkey->pk_strategy);
 		if (!OidIsValid(sortop))	/* should not happen */
-			elog(ERROR, "could not find member %d(%u,%u) of opfamily %u",
+			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
 				 pathkey->pk_strategy, pk_datatype, pk_datatype,
 				 pathkey->pk_opfamily);
 
@@ -6216,7 +6217,7 @@ make_unique_from_pathkeys(Plan *lefttree, List *pathkeys, int numCols)
 								   pk_datatype,
 								   BTEqualStrategyNumber);
 		if (!OidIsValid(eqop))	/* should not happen */
-			elog(ERROR, "could not find member %d(%u,%u) of opfamily %u",
+			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
 				 BTEqualStrategyNumber, pk_datatype, pk_datatype,
 				 pathkey->pk_opfamily);
 

src/backend/utils/cache/relcache.c

@@ -945,6 +945,10 @@ RelationBuildPartitionKey(Relation relation)
 								   opclassform->opcintype,
 								   opclassform->opcintype,
 								   BTORDER_PROC);
+		if (!OidIsValid(funcid))	/* should not happen */
+			elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
+				 BTORDER_PROC, opclassform->opcintype, opclassform->opcintype,
+				 opclassform->opcfamily);
 
 		fmgr_info(funcid, &key->partsupfunc[i]);