Change the way parse.y handles multi-row VALUES clauses to save a few cycles.

FossilOrigin-Name: 88d5bc91a52675d2a83748b79ad50de0e9732b2afd23107627bdc604f744d275
2025-11-11 01:42:22 +03:00 · 2024-03-13 20:04:11 +00:00
parent aa2e244e14
commit 56be6f6c08
5 changed files with 118 additions and 37 deletions
--- a/16
+++ b/16
@@ -1,5 +1,5 @@
-C Remove\sunreachable\scode\sfrom\sthis\sbranch.
-D 2024-03-13T18:41:05.450
+C Change\sthe\sway\sparse.y\shandles\smulti-row\sVALUES\sclauses\sto\ssave\sa\sfew\scycles.
+D 2024-03-13T20:04:11.997
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -709,7 +709,7 @@ F src/hash.c 9ee4269fb1d6632a6fecfb9479c93a1f29271bddbbaf215dd60420bcb80c7220
 F src/hash.h 3340ab6e1d13e725571d7cee6d3e3135f0779a7d8e76a9ce0a85971fa3953c51
 F src/hwtime.h f9c2dfb84dce7acf95ce6d289e46f5f9d3d1afd328e53da8f8e9008e3b3caae6
 F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
-F src/insert.c 05dd5ea1b8da8a81e1132140fd4dd6d4d9e777ee282799c53cce4f3e9d7dd0ca
+F src/insert.c 6323a2da33b5af954f914f33e06af30cce354bbd2553261a4b64e578339e498f
 F src/json.c e2e40760d6689134c3e2ece38c6a496b34ff5e2661a8f238444a119af666fdce
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 7432c944ff197046d67a1207790a1b13eec4548c85a9457eb0896bb3641dfb36
@@ -739,7 +739,7 @@ F src/os_win.c 6ff43bac175bd9ed79e7c0f96840b139f2f51d01689a638fd05128becf94908a
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c ff60e98138d2499082ac6230f01ac508aba545315debccfca2fd6042f5f10fcd
 F src/pager.h 4b1140d691860de0be1347474c51fee07d5420bd7f802d38cbab8ea4ab9f538a
-F src/parse.y 3d022ba4c68bf8c7c4c40b3e364d7a8226c4089fc9ff7a3a95f969f8f1bec959
+F src/parse.y 2ff84e5e346974100b7ed37f01abfd148012e1ce65a6b5a72d5025258077121e
 F src/pcache.c 040b165f30622a21b7a9a77c6f2e4877a32fb7f22d4c7f0d2a6fa6833a156a75
 F src/pcache.h 1497ce1b823cf00094bb0cf3bac37b345937e6f910890c626b16512316d3abf5
 F src/pcache1.c 602acb23c471bb8d557a6f0083cc2be641d6cafcafa19e481eba7ef4c9ca0f00
@@ -1921,7 +1921,7 @@ F test/vacuum4.test 7ea76b769fffeb41f925303b04cbcf5a5bbeabe55e4c60ae754ff24eeeb7
 F test/vacuum5.test 263b144d537e92ad8e9ca8a73cc6e1583f41cfd0dda9432b87f7806174a2f48c
 F test/vacuum6.test b137b04bf3392d3f5c3b8fda0ce85a6775a70ca112f6559f74ff52dc9ce042fd
 F test/vacuummem.test 4b30f5b95a9ff86e9d5c20741e50a898b2dc10b0962a3211571eb165357003fb
-F test/values.test 3f0fe0e8859306e9a5cfc800e327278762510c8d5b075d8ddce40f2d13d1405a
+F test/values.test 1f0a7f8468d7f087bc4add7a95545afb15e22d5e629a18fbea73b9d76f3ef8bd
 F test/valuesfault.test 2ef23ed965e3bd08e268cdc38a0d11653390ddbbe1e8e2e98d16f55edd30f6e8
 F test/varint.test bbce22cda8fc4d135bcc2b589574be8410614e62
 F test/veryquick.test 57ab846bacf7b90cf4e9a672721ea5c5b669b661
@@ -2179,8 +2179,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 2085c7f12a3916ec883c31795e29f2e2b6641c30ecf748cce9bff7b13b061d1f
-R 77c42a89dcd308559626c377320e4df2
+P 657c7b4f9df53e041a33cfad00ee2f507ac09c97a2ae61164bd189d660d167da
+R c74bcaf2a43ef6c41ceff5cdf5beeb0e
 U dan
-Z 54b19091c4c166a485c83de0a7190e37
+Z dc10b4e059ebbb23528a1aebd608a6c4
 # Remove this line to create a well-formed Fossil manifest.
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-657c7b4f9df53e041a33cfad00ee2f507ac09c97a2ae61164bd189d660d167da
+88d5bc91a52675d2a83748b79ad50de0e9732b2afd23107627bdc604f744d275
--- a/src/insert.c
+++ b/src/insert.c
@@ -577,6 +577,11 @@ void sqlite3AutoincrementEnd(Parse *pParse){
 # define autoIncStep(A,B,C)
 #endif /* SQLITE_OMIT_AUTOINCREMENT */

+/*
+** If argument pVal is a Select object returned by an sqlite3MultiValues()
+** that was able to use the co-routine optimization, finish coding the
+** co-routine.
+*/
 void sqlite3MultiValuesEnd(Parse *pParse, Select *pVal){
  if( pVal && pVal->pSrc->nSrc>0 ){
    SrcItem *pItem = &pVal->pSrc->a[0];
@@ -585,7 +590,11 @@ void sqlite3MultiValuesEnd(Parse *pParse, Select *pVal){
  }
 }

-static int multiValueIsConstant(ExprList *pRow){
+/*
+** Return true if all expressions in the expression-list passed as the
+** only argument are constant.
+*/
+static int exprListIsConstant(ExprList *pRow){
  int ii;
  for(ii=0; ii<pRow->nExpr; ii++){
    if( 0==sqlite3ExprIsConstant(pRow->a[ii].pExpr) ) return 0;
@@ -593,9 +602,13 @@ static int multiValueIsConstant(ExprList *pRow){
  return 1;
 }

-static int multiValueIsConstantNoAff(ExprList *pRow){
+/*
+** Return true if all expressions in the expression-list passed as the
+** only argument are both constant and have no affinity.
+*/
+static int exprListIsNoAffinity(ExprList *pRow){
  int ii;
-  if( multiValueIsConstant(pRow)==0 ) return 0;
+  if( exprListIsConstant(pRow)==0 ) return 0;
  for(ii=0; ii<pRow->nExpr; ii++){
    assert( pRow->a[ii].pExpr->affExpr==0 );
    if( 0!=sqlite3ExprAffinity(pRow->a[ii].pExpr) ) return 0;
@@ -606,17 +619,64 @@ static int multiValueIsConstantNoAff(ExprList *pRow){

 /*
 ** This function is called by the parser for the second and subsequent
-** rows of a multi-row VALUES clause.
+** rows of a multi-row VALUES clause. Argument pLeft is the part of
+** the VALUES clause already parsed, argument pRow is the vector of values
+** for the new row. The Select object returned represents the complete
+** VALUES clause, including the new row.
+**
+** There are two ways in which this may be achieved - by incremental 
+** coding of a co-routine (the "co-routine" method) or by returning a
+** Select object equivalent to the following (the "UNION ALL" method):
+**
+**        "pLeft UNION ALL SELECT pRow"
+**
+** If the VALUES clause contains a lot of rows, this compound Select
+** object may consume a lot of memory.
+**
+** When the co-routine method is used, each row that will be returned
+** by the VALUES clause is coded into part of a co-routine as it is 
+** passed to this function. The returned Select object is equivalent to:
+**
+**     SELECT * FROM (
+**       Select object to read co-routine
+**     )
+**
+** The co-routine method is used in most cases. Exceptions are:
+**
+**    a) If the current statement has a WITH clause. This is to avoid
+**       statements like:
+**
+**            WITH cte AS ( VALUES('x'), ('y') ... )
+**            SELECT * FROM cte AS a, cte AS b;
+**
+**       This will not work, as the co-routine uses a hard-coded register
+**       for its OP_Yield instructions, and so it is not possible for two
+**       cursors to iterate through it concurrently.
+**
+**    b) The schema is currently being parsed (i.e. the VALUES clause is part 
+**       of a schema item like a VIEW or TRIGGER). In this case there is no VM
+**       being generated when parsing is taking place, and so generating 
+**       a co-routine is not possible.
+**
+**    c) There are non-constant expressions in the VALUES clause (e.g.
+**       the VALUES clause is part of a correlated sub-query).
+**
+**    d) One or more of the values in the first row of the VALUES clause
+**       has an affinity (i.e. is a CAST expression). This causes problems
+**       because the complex rules SQLite uses (see function 
+**       sqlite3SubqueryColumnTypes() in select.c) to determine the effective
+**       affinity of such a column for all rows require access to all values in
+**       the column simultaneously. 
 */
 Select *sqlite3MultiValues(Parse *pParse, Select *pLeft, ExprList *pRow){

-  if( pLeft->pPrior
-   || pParse->bHasWith
-   || pParse->db->init.busy 
-   || multiValueIsConstant(pRow)==0
-   || (pLeft->pSrc->nSrc==0 && multiValueIsConstantNoAff(pLeft->pEList)==0)
+  if( pLeft->pPrior                    /* co-routine precluded by prior row */
+   || pParse->bHasWith                 /* condition (a) above */
+   || pParse->db->init.busy            /* condition (b) above */
+   || exprListIsConstant(pRow)==0      /* condition (c) above */
+   || (pLeft->pSrc->nSrc==0 && exprListIsNoAffinity(pLeft->pEList)==0) /* (d) */
  ){
-    /* This row of the VALUES clause cannot be coded immediately. */
+    /* The co-routine method cannot be used. Fall back to UNION ALL. */
    Select *pSelect = 0;
    int f = SF_Values | SF_MultiValue;
    if( pLeft->pSrc->nSrc ){
@@ -634,14 +694,14 @@ Select *sqlite3MultiValues(Parse *pParse, Select *pLeft, ExprList *pRow){
      pLeft = pSelect;
    }
  }else{
-    SrcItem *p = 0;
+    SrcItem *p = 0;               /* SrcItem that reads from co-routine */

    if( pLeft->pSrc->nSrc==0 ){
-      /* Co-routine has not yet been started. */
+      /* Co-routine has not yet been started and the special Select object
+      ** that accesses the co-routine has not yet been created. This block 
+      ** does both those things. */
      Vdbe *v = sqlite3GetVdbe(pParse);
-      Select *pRet;
-  
-      pRet = sqlite3SelectNew(pParse, 0, 0, 0, 0, 0, 0, 0, 0);
+      Select *pRet = sqlite3SelectNew(pParse, 0, 0, 0, 0, 0, 0, 0, 0);
      if( pRet ){
        SelectDest dest;
        pRet->pSrc->nSrc = 1;
--- a/src/parse.y
+++ b/src/parse.y
@@ -562,13 +562,10 @@ cmd ::= select(X).  {
 }

 %ifndef SQLITE_OMIT_CTE
-select(A) ::= withkw wqlist(W) selectnowith(X). {A = attachWithToSelect(pParse,X,W);}
-select(A) ::= withkw RECURSIVE wqlist(W) selectnowith(X).
+select(A) ::= WITH wqlist(W) selectnowith(X). {A = attachWithToSelect(pParse,X,W);}
+select(A) ::= WITH RECURSIVE wqlist(W) selectnowith(X).
                                              {A = attachWithToSelect(pParse,X,W);}

-withkw ::= WITH. {
-  pParse->bHasWith = 1;
-}
 %endif /* SQLITE_OMIT_CTE */
 select(A) ::= selectnowith(A). {
  Select *p = A;
@@ -626,16 +623,26 @@ oneselect(A) ::= SELECT distinct(D) selcollist(W) from(X) where_opt(Y)
 %endif


-oneselect(A) ::= values(A). {
-  sqlite3MultiValuesEnd(pParse, A);
-}
-
+// Single row VALUES clause.
+//
 %type values {Select*}
+oneselect(A) ::= values(A).
 %destructor values {sqlite3SelectDelete(pParse->db, $$);}
 values(A) ::= VALUES LP nexprlist(X) RP. {
  A = sqlite3SelectNew(pParse,X,0,0,0,0,0,SF_Values,0);
 }
-values(A) ::= values(A) COMMA LP nexprlist(Y) RP. {
+
+// Multiple row VALUES clause.
+//
+%type mvalues {Select*}
+oneselect(A) ::= mvalues(A). {
+  sqlite3MultiValuesEnd(pParse, A);
+}
+%destructor mvalues {sqlite3SelectDelete(pParse->db, $$);}
+mvalues(A) ::= values(A) COMMA LP nexprlist(Y) RP. {
+  A = sqlite3MultiValues(pParse, A, Y);
+}
+mvalues(A) ::= mvalues(A) COMMA LP nexprlist(Y) RP. {
  A = sqlite3MultiValues(pParse, A, Y);
 }

@@ -1751,16 +1758,17 @@ anylist ::= anylist ANY.

 with ::= .
 %ifndef SQLITE_OMIT_CTE
-with ::= withkw wqlist(W).              { sqlite3WithPush(pParse, W, 1); }
-with ::= withkw RECURSIVE wqlist(W).    { sqlite3WithPush(pParse, W, 1); }
+with ::= WITH wqlist(W).              { sqlite3WithPush(pParse, W, 1); }
+with ::= WITH RECURSIVE wqlist(W).    { sqlite3WithPush(pParse, W, 1); }

 %type wqas {u8}
 wqas(A)   ::= AS.                  {A = M10d_Any;}
 wqas(A)   ::= AS MATERIALIZED.     {A = M10d_Yes;}
 wqas(A)   ::= AS NOT MATERIALIZED. {A = M10d_No;}
-wqitem(A) ::= nm(X) eidlist_opt(Y) wqas(M) LP select(Z) RP. {
+wqitem(A) ::= withnm(X) eidlist_opt(Y) wqas(M) LP select(Z) RP. {
  A = sqlite3CteNew(pParse, &X, Y, Z, M); /*A-overwrites-X*/
 }
+withnm(A) ::= nm(A). {pParse->bHasWith = 1;}
 wqlist(A) ::= wqitem(X). {
  A = sqlite3WithAdd(pParse, 0, X); /*A-overwrites-X*/
 }
--- a/test/values.test
+++ b/test/values.test
@@ -267,5 +267,18 @@ do_execsql_test 6.2 {
  VALUES(CAST(44 AS REAL)),(55);
 } {44.0 55}

+#------------------------------------------------------------------------
+do_execsql_test 7.1 {
+  WITH x1(a, b) AS (
+    VALUES(1, 2), ('a', 'b')
+  )
+  SELECT * FROM x1 one, x1 two
+} {
+  1 2  1 2
+  1 2  a b
+  a b  1 2
+  a b  a b
+}
+
 finish_test