Begin adding the data-structure explaining subsystem. All is contained within
FossilOrigin-Name: 79ae51c5b1b20ed0a425a87e65a32a096a80b7e1
diff --git a/src/expr.c b/src/expr.c
index e8a9d64..d157743 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -2939,6 +2939,56 @@
return inReg;
}
+#if defined(SQLITE_DEBUG)
+/*
+** Generate a human-readable explanation of an expression tree.
+*/
+void sqlite3ExplainExpr(Vdbe *pOut, Expr *p){
+ if( p==0 ){
+ sqlite3ExplainPrintf(pOut, "(C-null)");
+ return;
+ }
+ if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
+ sqlite3ExplainPrintf(pOut, "(%s", p->u.zToken);
+ }else{
+ sqlite3ExplainPrintf(pOut, "(op=%d", p->op);
+ }
+ if( p->pLeft ){
+ sqlite3ExplainPrintf(pOut, " left=");
+ sqlite3ExplainExpr(pOut, p->pLeft);
+ }
+ if( p->pRight ){
+ sqlite3ExplainPrintf(pOut, " right=");
+ sqlite3ExplainExpr(pOut, p->pRight);
+ }
+ sqlite3ExplainPrintf(pOut, ")");
+}
+#endif /* defined(SQLITE_DEBUG) */
+
+#if defined(SQLITE_DEBUG)
+/*
+** Generate a human-readable explanation of an expression list.
+*/
+void sqlite3ExplainExprList(Vdbe *pOut, ExprList *pList){
+ int i;
+ if( pList==0 ){
+ sqlite3ExplainPrintf(pOut, "(empty-list)");
+ return;
+ }
+ sqlite3ExplainPush(pOut);
+ for(i=0; i<pList->nExpr; i++){
+ sqlite3ExplainPrintf(pOut, "%02d: ", i);
+ sqlite3ExplainPush(pOut);
+ sqlite3ExplainExpr(pOut, pList->a[i].pExpr);
+ sqlite3ExplainPop(pOut);
+ if( i<pList->nExpr-1 ){
+ sqlite3ExplainNL(pOut);
+ }
+ }
+ sqlite3ExplainPop(pOut);
+}
+#endif /* SQLITE_DEBUG */
+
/*
** Return TRUE if pExpr is an constant expression that is appropriate
** for factoring out of a loop. Appropriate expressions are: