Do not run the subroutine that materializes a view or subquery until just

before the materialization is actually needed, so that if the materialization
turns out to never been needed, unnecessary work can be avoided.

FossilOrigin-Name: d64ae49a1f2513171d678259928c67741d79b2ae595078299525641a676cc46b

manifest

@@ -1,5 +1,5 @@
-C WASM:\sremoved\sthe\sin64-related\sbindings,\sas\sMDN\ssays\sthat\scalling\sa\swasm\sfunction\swhich\shas\san\sint64\stype\sin\sits\ssignature\swill\scurrently\sthrow\sbecause\sJS\shas\sno\s64-bit\sinteger\ssupport.\sThose\sbindings\snow\suse\sdoubles\sand\ssimply\shope\sthat\sthe\suser\sdoesn't\sexceed\stheir\sinteger\sprecision\s(2^53-1,\sapprox\s9\squadrillion).
-D 2022-05-23T01:11:49.315
+C Do\snot\srun\sthe\ssubroutine\sthat\smaterializes\sa\sview\sor\ssubquery\suntil\sjust\nbefore\sthe\smaterialization\sis\sactually\sneeded,\sso\sthat\sif\sthe\smaterialization\nturns\sout\sto\snever\sbeen\sneeded,\sunnecessary\swork\scan\sbe\savoided.
+D 2022-05-23T10:57:20.868
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -566,12 +566,12 @@ F src/printf.c 6166a30417b05c5b2f82e1f183f75faa2926ad60531c0b688a57dbc951441a20
 F src/random.c 097dc8b31b8fba5a9aca1697aeb9fd82078ec91be734c16bffda620ced7ab83c
 F src/resolve.c a4eb3c617027fd049b07432f3b942ea7151fa793a332a11a7d0f58c9539e104f
 F src/rowset.c ba9515a922af32abe1f7d39406b9d35730ed65efab9443dc5702693b60854c92
-F src/select.c 74060a09f66c0c056f3c61627e22cb484af0bbfa29d7d14dcf17c684742c15de
+F src/select.c 4f13d01141caae4f982125fecf50703c746ab621c57ca0aa747fab2b28e88c1e
 F src/shell.c.in 55d71bf8c7a8f2a66bc5f99cd76f226790b291599b83415533dad84a553ed806
 F src/sqlite.h.in d15c307939039086adca159dd340a94b79b69827e74c6d661f343eeeaefba896
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h a988810c9b21c0dc36dc7a62735012339dc76fc7ab448fb0792721d30eacb69d
-F src/sqliteInt.h fbe2d12cc13e80ac88c69ecde5ef9f052025fba78aa10f3eed0c71a5302e9a76
+F src/sqliteInt.h 3064533677f135771e71843b5221482df18d6589afe65e6a7ef828ccb8879a5f
 F src/sqliteLimit.h d7323ffea5208c6af2734574bae933ca8ed2ab728083caa117c9738581a31657
 F src/status.c 4a3da6d77eeb3531cb0dbdf7047772a2a1b99f98c69e90ce009c75fe6328b2c0
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -653,7 +653,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c b9df133a705093da8977da5eb202eaadb844839f1c7297c08d33471f5491843d
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c f890a3298418d7cba3b69b8803594fdc484ea241206a8dfa99db6dd36f8cbb3b
-F src/where.c 2ee27fed4a5564cddfc6710a539037d18e39e75cdf90b3f48d476c3b9767592e
+F src/where.c 226b9b5485d101fe4f99db2a7a1ce3fc2ab5be270b539817fd7dcbefdbfd440a
 F src/whereInt.h 8da918f392bf202ccc0ee61291455b33ad171d209445f1ff3eaf62e0b6f6b363
 F src/wherecode.c 2a8a73bcf1886632f2b2247c79395f94852a4b74484d8aa70a005892ce73d339
 F src/whereexpr.c efed370c684dce04eab949202c5452bbde993efb198de43c7a88f59411ad2a2c
@@ -1967,8 +1967,9 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0d6332f706ec5c34cc6a9ff79878f4e10a9ad81b24cc7d743b52168586285811
-R 79562a6f4ad568e3ba19c4e1026944bf
-U stephan
-Z 5fc9a3781b7c2550ee7ad879a95eb45a
+P 392e84828275ec203bc713d3a5d4790852add57539add6b29b5f6de1da2dc97a 16bf350683fd6ac906dbd02b21fb8bf1b1014ed05594cacf108645acd383ae65
+R b08060ca43b78ebd2d297e7f5a17d817
+T +closed 16bf350683fd6ac906dbd02b21fb8bf1b1014ed05594cacf108645acd383ae65
+U drh
+Z be8900ebd686c65db6085318ddd46fbb
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-392e84828275ec203bc713d3a5d4790852add57539add6b29b5f6de1da2dc97a
+d64ae49a1f2513171d678259928c67741d79b2ae595078299525641a676cc46b

src/select.c

@@ -6905,7 +6905,7 @@ int sqlite3Select(
 
     /* Generate code to implement the subquery
     **
-    ** The subquery is implemented as a co-routine all of the following are
+    ** The subquery is implemented as a co-routine all if the following are
     ** true:
     **
     **    (1)  the subquery is guaranteed to be the outer loop (so that
@@ -6963,11 +6963,11 @@ int sqlite3Select(
       ** the same view can reuse the materialization. */
       int topAddr;
       int onceAddr = 0;
-      int retAddr;
 
       pItem->regReturn = ++pParse->nMem;
-      topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
+      topAddr = sqlite3VdbeAddOp0(v, OP_Goto);
       pItem->addrFillSub = topAddr+1;
+      pItem->fg.isMaterialized = 1;
       if( pItem->fg.isCorrelated==0 ){
         /* If the subquery is not correlated and if we are not inside of
         ** a trigger, then we only need to compute the value of the subquery
@@ -6982,9 +6982,9 @@ int sqlite3Select(
       sqlite3Select(pParse, pSub, &dest);
       pItem->pTab->nRowLogEst = pSub->nSelectRow;
       if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
-      retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);
+      sqlite3VdbeAddOp2(v, OP_Return, pItem->regReturn, topAddr+1);
       VdbeComment((v, "end %!S", pItem));
-      sqlite3VdbeChangeP1(v, topAddr, retAddr);
+      sqlite3VdbeJumpHere(v, topAddr);
       sqlite3ClearTempRegCache(pParse);
       if( pItem->fg.isCte && pItem->fg.isCorrelated==0 ){
         CteUse *pCteUse = pItem->u2.pCteUse;

src/sqliteInt.h

@@ -3093,6 +3093,7 @@ struct SrcItem {
     unsigned isIndexedBy :1;   /* True if there is an INDEXED BY clause */
     unsigned isTabFunc :1;     /* True if table-valued-function syntax */
     unsigned isCorrelated :1;  /* True if sub-query is correlated */
+    unsigned isMaterialized:1; /* This is a materialized view */
     unsigned viaCoroutine :1;  /* Implemented as a co-routine */
     unsigned isRecursive :1;   /* True for recursive reference in WITH */
     unsigned fromDDL :1;       /* Comes from sqlite_schema */

src/where.c

@@ -5847,6 +5847,7 @@ WhereInfo *sqlite3WhereBegin(
         iIndexCur = pParse->nTab++;
       }
       pLevel->iIdxCur = iIndexCur;
+      assert( pIx!=0 );
       assert( pIx->pSchema==pTab->pSchema );
       assert( iIndexCur>=0 );
       if( op ){
@@ -5922,9 +5923,20 @@ WhereInfo *sqlite3WhereBegin(
   for(ii=0; ii<nTabList; ii++){
     int addrExplain;
     int wsFlags;
+    SrcItem *pSrc;
     if( pParse->nErr ) goto whereBeginError;
     pLevel = &pWInfo->a[ii];
     wsFlags = pLevel->pWLoop->wsFlags;
+    pSrc = &pTabList->a[pLevel->iFrom];
+    if( pSrc->fg.isMaterialized ){
+      if( pSrc->fg.isCorrelated ){
+        sqlite3VdbeAddOp2(v, OP_Gosub, pSrc->regReturn, pSrc->addrFillSub);
+      }else{
+        int iOnce = sqlite3VdbeAddOp0(v, OP_Once);
+        sqlite3VdbeAddOp2(v, OP_Gosub, pSrc->regReturn, pSrc->addrFillSub);
+        sqlite3VdbeJumpHere(v, iOnce);
+      }
+    }
     if( (wsFlags & (WHERE_AUTO_INDEX|WHERE_BLOOMFILTER))!=0 ){
       if( (wsFlags & WHERE_AUTO_INDEX)!=0 ){
 #ifndef SQLITE_OMIT_AUTOMATIC_INDEX