--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/persistentstorage/sql/SQLite/update.c Fri Jan 22 11:06:30 2010 +0200
@@ -0,0 +1,678 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code. In place of
+** a legal notice, here is a blessing:
+**
+** May you do good and not evil.
+** May you find forgiveness for yourself and forgive others.
+** May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle UPDATE statements.
+**
+** $Id: update.c,v 1.181 2008/07/28 19:34:54 drh Exp $
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Forward declaration */
+static void updateVirtualTable(
+ Parse *pParse, /* The parsing context */
+ SrcList *pSrc, /* The virtual table to be modified */
+ Table *pTab, /* The virtual table */
+ ExprList *pChanges, /* The columns to change in the UPDATE statement */
+ Expr *pRowidExpr, /* Expression used to recompute the rowid */
+ int *aXRef, /* Mapping from columns of pTab to entries in pChanges */
+ Expr *pWhere /* WHERE clause of the UPDATE statement */
+);
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** The most recently coded instruction was an OP_Column to retrieve the
+** i-th column of table pTab. This routine sets the P4 parameter of the
+** OP_Column to the default value, if any.
+**
+** The default value of a column is specified by a DEFAULT clause in the
+** column definition. This was either supplied by the user when the table
+** was created, or added later to the table definition by an ALTER TABLE
+** command. If the latter, then the row-records in the table btree on disk
+** may not contain a value for the column and the default value, taken
+** from the P4 parameter of the OP_Column instruction, is returned instead.
+** If the former, then all row-records are guaranteed to include a value
+** for the column and the P4 value is not required.
+**
+** Column definitions created by an ALTER TABLE command may only have
+** literal default values specified: a number, null or a string. (If a more
+** complicated default expression value was provided, it is evaluated
+** when the ALTER TABLE is executed and one of the literal values written
+** into the sqlite_master table.)
+**
+** Therefore, the P4 parameter is only required if the default value for
+** the column is a literal number, string or null. The sqlite3ValueFromExpr()
+** function is capable of transforming these types of expressions into
+** sqlite3_value objects.
+*/
+void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i){
+ if( pTab && !pTab->pSelect ){
+ sqlite3_value *pValue;
+ u8 enc = ENC(sqlite3VdbeDb(v));
+ Column *pCol = &pTab->aCol[i];
+ VdbeComment((v, "%s.%s", pTab->zName, pCol->zName));
+ assert( i<pTab->nCol );
+ sqlite3ValueFromExpr(sqlite3VdbeDb(v), pCol->pDflt, enc,
+ pCol->affinity, &pValue);
+ if( pValue ){
+ sqlite3VdbeChangeP4(v, -1, (const char *)pValue, P4_MEM);
+ }
+ }
+}
+
+/*
+** Process an UPDATE statement.
+**
+** UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;
+** \_______/ \________/ \______/ \________________/
+* onError pTabList pChanges pWhere
+*/
+void sqlite3Update(
+ Parse *pParse, /* The parser context */
+ SrcList *pTabList, /* The table in which we should change things */
+ ExprList *pChanges, /* Things to be changed */
+ Expr *pWhere, /* The WHERE clause. May be null */
+ int onError /* How to handle constraint errors */
+){
+ int i, j; /* Loop counters */
+ Table *pTab; /* The table to be updated */
+ int addr = 0; /* VDBE instruction address of the start of the loop */
+ WhereInfo *pWInfo; /* Information about the WHERE clause */
+ Vdbe *v; /* The virtual database engine */
+ Index *pIdx; /* For looping over indices */
+ int nIdx; /* Number of indices that need updating */
+ int iCur; /* VDBE Cursor number of pTab */
+ sqlite3 *db; /* The database structure */
+ int *aRegIdx = 0; /* One register assigned to each index to be updated */
+ int *aXRef = 0; /* aXRef[i] is the index in pChanges->a[] of the
+ ** an expression for the i-th column of the table.
+ ** aXRef[i]==-1 if the i-th column is not changed. */
+ int chngRowid; /* True if the record number is being changed */
+ Expr *pRowidExpr = 0; /* Expression defining the new record number */
+ int openAll = 0; /* True if all indices need to be opened */
+ AuthContext sContext; /* The authorization context */
+ NameContext sNC; /* The name-context to resolve expressions in */
+ int iDb; /* Database containing the table being updated */
+ int j1; /* Addresses of jump instructions */
+ int okOnePass; /* True for one-pass algorithm without the FIFO */
+
+#ifndef SQLITE_OMIT_TRIGGER
+ int isView; /* Trying to update a view */
+ int triggers_exist = 0; /* True if any row triggers exist */
+#endif
+ int iBeginAfterTrigger; /* Address of after trigger program */
+ int iEndAfterTrigger; /* Exit of after trigger program */
+ int iBeginBeforeTrigger; /* Address of before trigger program */
+ int iEndBeforeTrigger; /* Exit of before trigger program */
+ u32 old_col_mask = 0; /* Mask of OLD.* columns in use */
+ u32 new_col_mask = 0; /* Mask of NEW.* columns in use */
+
+ int newIdx = -1; /* index of trigger "new" temp table */
+ int oldIdx = -1; /* index of trigger "old" temp table */
+
+ /* Register Allocations */
+ int regRowCount = 0; /* A count of rows changed */
+ int regOldRowid; /* The old rowid */
+ int regNewRowid; /* The new rowid */
+ int regData; /* New data for the row */
+
+ sContext.pParse = 0;
+ db = pParse->db;
+ if( pParse->nErr || db->mallocFailed ){
+ goto update_cleanup;
+ }
+ assert( pTabList->nSrc==1 );
+
+ /* Locate the table which we want to update.
+ */
+ pTab = sqlite3SrcListLookup(pParse, pTabList);
+ if( pTab==0 ) goto update_cleanup;
+ iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+
+ /* Figure out if we have any triggers and if the table being
+ ** updated is a view
+ */
+#ifndef SQLITE_OMIT_TRIGGER
+ triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges);
+ isView = pTab->pSelect!=0;
+#else
+# define triggers_exist 0
+# define isView 0
+#endif
+#ifdef SQLITE_OMIT_VIEW
+# undef isView
+# define isView 0
+#endif
+
+ if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
+ goto update_cleanup;
+ }
+ if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+ goto update_cleanup;
+ }
+ aXRef = sqlite3DbMallocRaw(db, sizeof(int) * pTab->nCol );
+ if( aXRef==0 ) goto update_cleanup;
+ for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
+
+ /* If there are FOR EACH ROW triggers, allocate cursors for the
+ ** special OLD and NEW tables
+ */
+ if( triggers_exist ){
+ newIdx = pParse->nTab++;
+ oldIdx = pParse->nTab++;
+ }
+
+ /* Allocate a cursors for the main database table and for all indices.
+ ** The index cursors might not be used, but if they are used they
+ ** need to occur right after the database cursor. So go ahead and
+ ** allocate enough space, just in case.
+ */
+ pTabList->a[0].iCursor = iCur = pParse->nTab++;
+ for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+ pParse->nTab++;
+ }
+
+ /* Initialize the name-context */
+ memset(&sNC, 0, sizeof(sNC));
+ sNC.pParse = pParse;
+ sNC.pSrcList = pTabList;
+
+ /* Resolve the column names in all the expressions of the
+ ** of the UPDATE statement. Also find the column index
+ ** for each column to be updated in the pChanges array. For each
+ ** column to be updated, make sure we have authorization to change
+ ** that column.
+ */
+ chngRowid = 0;
+ for(i=0; i<pChanges->nExpr; i++){
+ if( sqlite3ExprResolveNames(&sNC, pChanges->a[i].pExpr) ){
+ goto update_cleanup;
+ }
+ for(j=0; j<pTab->nCol; j++){
+ if( sqlite3StrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){
+ if( j==pTab->iPKey ){
+ chngRowid = 1;
+ pRowidExpr = pChanges->a[i].pExpr;
+ }
+ aXRef[j] = i;
+ break;
+ }
+ }
+ if( j>=pTab->nCol ){
+ if( sqlite3IsRowid(pChanges->a[i].zName) ){
+ chngRowid = 1;
+ pRowidExpr = pChanges->a[i].pExpr;
+ }else{
+ sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);
+ goto update_cleanup;
+ }
+ }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+ {
+ int rc;
+ rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
+ pTab->aCol[j].zName, db->aDb[iDb].zName);
+ if( rc==SQLITE_DENY ){
+ goto update_cleanup;
+ }else if( rc==SQLITE_IGNORE ){
+ aXRef[j] = -1;
+ }
+ }
+#endif
+ }
+
+ /* Allocate memory for the array aRegIdx[]. There is one entry in the
+ ** array for each index associated with table being updated. Fill in
+ ** the value with a register number for indices that are to be used
+ ** and with zero for unused indices.
+ */
+ for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){}
+ if( nIdx>0 ){
+ aRegIdx = sqlite3DbMallocRaw(db, sizeof(Index*) * nIdx );
+ if( aRegIdx==0 ) goto update_cleanup;
+ }
+ for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+ int reg;
+ if( chngRowid ){
+ reg = ++pParse->nMem;
+ }else{
+ reg = 0;
+ for(i=0; i<pIdx->nColumn; i++){
+ if( aXRef[pIdx->aiColumn[i]]>=0 ){
+ reg = ++pParse->nMem;
+ break;
+ }
+ }
+ }
+ aRegIdx[j] = reg;
+ }
+
+ /* Allocate a block of register used to store the change record
+ ** sent to sqlite3GenerateConstraintChecks(). There are either
+ ** one or two registers for holding the rowid. One rowid register
+ ** is used if chngRowid is false and two are used if chngRowid is
+ ** true. Following these are pTab->nCol register holding column
+ ** data.
+ */
+ regOldRowid = regNewRowid = pParse->nMem + 1;
+ pParse->nMem += pTab->nCol + 1;
+ if( chngRowid ){
+ regNewRowid++;
+ pParse->nMem++;
+ }
+ regData = regNewRowid+1;
+
+
+ /* Begin generating code.
+ */
+ v = sqlite3GetVdbe(pParse);
+ if( v==0 ) goto update_cleanup;
+ if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
+ sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ /* Virtual tables must be handled separately */
+ if( IsVirtual(pTab) ){
+ updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
+ pWhere);
+ pWhere = 0;
+ pTabList = 0;
+ goto update_cleanup;
+ }
+#endif
+
+ /* Start the view context
+ */
+ if( isView ){
+ sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
+ }
+
+ /* Generate the code for triggers.
+ */
+ if( triggers_exist ){
+ int iGoto;
+
+ /* Create pseudo-tables for NEW and OLD
+ */
+ sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);
+ sqlite3VdbeAddOp2(v, OP_OpenPseudo, oldIdx, 0);
+ sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);
+ sqlite3VdbeAddOp2(v, OP_OpenPseudo, newIdx, 0);
+
+ iGoto = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
+ addr = sqlite3VdbeMakeLabel(v);
+ iBeginBeforeTrigger = sqlite3VdbeCurrentAddr(v);
+ if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_BEFORE, pTab,
+ newIdx, oldIdx, onError, addr, &old_col_mask, &new_col_mask) ){
+ goto update_cleanup;
+ }
+ iEndBeforeTrigger = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
+ iBeginAfterTrigger = sqlite3VdbeCurrentAddr(v);
+ if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_AFTER, pTab,
+ newIdx, oldIdx, onError, addr, &old_col_mask, &new_col_mask) ){
+ goto update_cleanup;
+ }
+ iEndAfterTrigger = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
+ sqlite3VdbeJumpHere(v, iGoto);
+ }
+
+ /* If we are trying to update a view, realize that view into
+ ** a ephemeral table.
+ */
+ if( isView ){
+ sqlite3MaterializeView(pParse, pTab->pSelect, pWhere, iCur);
+ }
+
+ /* Resolve the column names in all the expressions in the
+ ** WHERE clause.
+ */
+ if( sqlite3ExprResolveNames(&sNC, pWhere) ){
+ goto update_cleanup;
+ }
+
+ /* Begin the database scan
+ */
+ sqlite3VdbeAddOp2(v, OP_Null, 0, regOldRowid);
+ pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0,
+ WHERE_ONEPASS_DESIRED);
+ if( pWInfo==0 ) goto update_cleanup;
+ okOnePass = pWInfo->okOnePass;
+
+ /* Remember the rowid of every item to be updated.
+ */
+ sqlite3VdbeAddOp2(v, IsVirtual(pTab)?OP_VRowid:OP_Rowid, iCur, regOldRowid);
+ if( !okOnePass ) sqlite3VdbeAddOp2(v, OP_FifoWrite, regOldRowid, 0);
+
+ /* End the database scan loop.
+ */
+ sqlite3WhereEnd(pWInfo);
+
+ /* Initialize the count of updated rows
+ */
+ if( db->flags & SQLITE_CountRows && !pParse->trigStack ){
+ regRowCount = ++pParse->nMem;
+ sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
+ }
+
+ if( !isView && !IsVirtual(pTab) ){
+ /*
+ ** Open every index that needs updating. Note that if any
+ ** index could potentially invoke a REPLACE conflict resolution
+ ** action, then we need to open all indices because we might need
+ ** to be deleting some records.
+ */
+ if( !okOnePass ) sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite);
+ if( onError==OE_Replace ){
+ openAll = 1;
+ }else{
+ openAll = 0;
+ for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+ if( pIdx->onError==OE_Replace ){
+ openAll = 1;
+ break;
+ }
+ }
+ }
+ for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
+ if( openAll || aRegIdx[i]>0 ){
+ KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
+ sqlite3VdbeAddOp4(v, OP_OpenWrite, iCur+i+1, pIdx->tnum, iDb,
+ (char*)pKey, P4_KEYINFO_HANDOFF);
+ assert( pParse->nTab>iCur+i+1 );
+ }
+ }
+ }
+
+ /* Jump back to this point if a trigger encounters an IGNORE constraint. */
+ if( triggers_exist ){
+ sqlite3VdbeResolveLabel(v, addr);
+ }
+
+ /* Top of the update loop */
+ if( okOnePass ){
+ int a1 = sqlite3VdbeAddOp1(v, OP_NotNull, regOldRowid);
+ addr = sqlite3VdbeAddOp0(v, OP_Goto);
+ sqlite3VdbeJumpHere(v, a1);
+ }else{
+ addr = sqlite3VdbeAddOp2(v, OP_FifoRead, regOldRowid, 0);
+ }
+
+ if( triggers_exist ){
+ int regRowid;
+ int regRow;
+ int regCols;
+
+ /* Make cursor iCur point to the record that is being updated.
+ */
+ sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);
+
+ /* Generate the OLD table
+ */
+ regRowid = sqlite3GetTempReg(pParse);
+ regRow = sqlite3GetTempReg(pParse);
+ sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regRowid);
+ if( !old_col_mask ){
+ sqlite3VdbeAddOp2(v, OP_Null, 0, regRow);
+ }else{
+ sqlite3VdbeAddOp2(v, OP_RowData, iCur, regRow);
+ }
+ sqlite3VdbeAddOp3(v, OP_Insert, oldIdx, regRow, regRowid);
+
+ /* Generate the NEW table
+ */
+ if( chngRowid ){
+ sqlite3ExprCodeAndCache(pParse, pRowidExpr, regRowid);
+ }else{
+ sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regRowid);
+ }
+ regCols = sqlite3GetTempRange(pParse, pTab->nCol);
+ for(i=0; i<pTab->nCol; i++){
+ if( i==pTab->iPKey ){
+ sqlite3VdbeAddOp2(v, OP_Null, 0, regCols+i);
+ continue;
+ }
+ j = aXRef[i];
+ if( new_col_mask&((u32)1<<i) || new_col_mask==0xffffffff ){
+ if( j<0 ){
+ sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regCols+i);
+ sqlite3ColumnDefault(v, pTab, i);
+ }else{
+ sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr, regCols+i);
+ }
+ }else{
+ sqlite3VdbeAddOp2(v, OP_Null, 0, regCols+i);
+ }
+ }
+ sqlite3VdbeAddOp3(v, OP_MakeRecord, regCols, pTab->nCol, regRow);
+ if( !isView ){
+ sqlite3TableAffinityStr(v, pTab);
+ sqlite3ExprCacheAffinityChange(pParse, regCols, pTab->nCol);
+ }
+ sqlite3ReleaseTempRange(pParse, regCols, pTab->nCol);
+ /* if( pParse->nErr ) goto update_cleanup; */
+ sqlite3VdbeAddOp3(v, OP_Insert, newIdx, regRow, regRowid);
+ sqlite3ReleaseTempReg(pParse, regRowid);
+ sqlite3ReleaseTempReg(pParse, regRow);
+
+ sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginBeforeTrigger);
+ sqlite3VdbeJumpHere(v, iEndBeforeTrigger);
+ }
+
+ if( !isView && !IsVirtual(pTab) ){
+ /* Loop over every record that needs updating. We have to load
+ ** the old data for each record to be updated because some columns
+ ** might not change and we will need to copy the old value.
+ ** Also, the old data is needed to delete the old index entries.
+ ** So make the cursor point at the old record.
+ */
+ sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);
+
+ /* If the record number will change, push the record number as it
+ ** will be after the update. (The old record number is currently
+ ** on top of the stack.)
+ */
+ if( chngRowid ){
+ sqlite3ExprCode(pParse, pRowidExpr, regNewRowid);
+ sqlite3VdbeAddOp1(v, OP_MustBeInt, regNewRowid);
+ }
+
+ /* Compute new data for this record.
+ */
+ for(i=0; i<pTab->nCol; i++){
+ if( i==pTab->iPKey ){
+ sqlite3VdbeAddOp2(v, OP_Null, 0, regData+i);
+ continue;
+ }
+ j = aXRef[i];
+ if( j<0 ){
+ sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regData+i);
+ sqlite3ColumnDefault(v, pTab, i);
+ }else{
+ sqlite3ExprCode(pParse, pChanges->a[j].pExpr, regData+i);
+ }
+ }
+
+ /* Do constraint checks
+ */
+ sqlite3GenerateConstraintChecks(pParse, pTab, iCur, regNewRowid,
+ aRegIdx, chngRowid, 1,
+ onError, addr);
+
+ /* Delete the old indices for the current record.
+ */
+ j1 = sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regOldRowid);
+ sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, aRegIdx);
+
+ /* If changing the record number, delete the old record.
+ */
+ if( chngRowid ){
+ sqlite3VdbeAddOp2(v, OP_Delete, iCur, 0);
+ }
+ sqlite3VdbeJumpHere(v, j1);
+
+ /* Create the new index entries and the new record.
+ */
+ sqlite3CompleteInsertion(pParse, pTab, iCur, regNewRowid,
+ aRegIdx, chngRowid, 1, -1, 0);
+ }
+
+ /* Increment the row counter
+ */
+ if( db->flags & SQLITE_CountRows && !pParse->trigStack){
+ sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
+ }
+
+ /* If there are triggers, close all the cursors after each iteration
+ ** through the loop. The fire the after triggers.
+ */
+ if( triggers_exist ){
+ sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginAfterTrigger);
+ sqlite3VdbeJumpHere(v, iEndAfterTrigger);
+ }
+
+ /* Repeat the above with the next record to be updated, until
+ ** all record selected by the WHERE clause have been updated.
+ */
+ sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
+ sqlite3VdbeJumpHere(v, addr);
+
+ /* Close all tables */
+ for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
+ if( openAll || aRegIdx[i]>0 ){
+ sqlite3VdbeAddOp2(v, OP_Close, iCur+i+1, 0);
+ }
+ }
+ sqlite3VdbeAddOp2(v, OP_Close, iCur, 0);
+ if( triggers_exist ){
+ sqlite3VdbeAddOp2(v, OP_Close, newIdx, 0);
+ sqlite3VdbeAddOp2(v, OP_Close, oldIdx, 0);
+ }
+
+ /*
+ ** Return the number of rows that were changed. If this routine is
+ ** generating code because of a call to sqlite3NestedParse(), do not
+ ** invoke the callback function.
+ */
+ if( db->flags & SQLITE_CountRows && !pParse->trigStack && pParse->nested==0 ){
+ sqlite3VdbeAddOp2(v, OP_ResultRow, regRowCount, 1);
+ sqlite3VdbeSetNumCols(v, 1);
+ sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", P4_STATIC);
+ }
+
+update_cleanup:
+ sqlite3AuthContextPop(&sContext);
+ sqlite3DbFree(db, aRegIdx);
+ sqlite3DbFree(db, aXRef);
+ sqlite3SrcListDelete(db, pTabList);
+ sqlite3ExprListDelete(db, pChanges);
+ sqlite3ExprDelete(db, pWhere);
+ return;
+}
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Generate code for an UPDATE of a virtual table.
+**
+** The strategy is that we create an ephemerial table that contains
+** for each row to be changed:
+**
+** (A) The original rowid of that row.
+** (B) The revised rowid for the row. (note1)
+** (C) The content of every column in the row.
+**
+** Then we loop over this ephemeral table and for each row in
+** the ephermeral table call VUpdate.
+**
+** When finished, drop the ephemeral table.
+**
+** (note1) Actually, if we know in advance that (A) is always the same
+** as (B) we only store (A), then duplicate (A) when pulling
+** it out of the ephemeral table before calling VUpdate.
+*/
+static void updateVirtualTable(
+ Parse *pParse, /* The parsing context */
+ SrcList *pSrc, /* The virtual table to be modified */
+ Table *pTab, /* The virtual table */
+ ExprList *pChanges, /* The columns to change in the UPDATE statement */
+ Expr *pRowid, /* Expression used to recompute the rowid */
+ int *aXRef, /* Mapping from columns of pTab to entries in pChanges */
+ Expr *pWhere /* WHERE clause of the UPDATE statement */
+){
+ Vdbe *v = pParse->pVdbe; /* Virtual machine under construction */
+ ExprList *pEList = 0; /* The result set of the SELECT statement */
+ Select *pSelect = 0; /* The SELECT statement */
+ Expr *pExpr; /* Temporary expression */
+ int ephemTab; /* Table holding the result of the SELECT */
+ int i; /* Loop counter */
+ int addr; /* Address of top of loop */
+ int iReg; /* First register in set passed to OP_VUpdate */
+ sqlite3 *db = pParse->db; /* Database connection */
+ const char *pVtab = (const char*)pTab->pVtab;
+ SelectDest dest;
+
+ /* Construct the SELECT statement that will find the new values for
+ ** all updated rows.
+ */
+ pEList = sqlite3ExprListAppend(pParse, 0,
+ sqlite3CreateIdExpr(pParse, "_rowid_"), 0);
+ if( pRowid ){
+ pEList = sqlite3ExprListAppend(pParse, pEList,
+ sqlite3ExprDup(db, pRowid), 0);
+ }
+ assert( pTab->iPKey<0 );
+ for(i=0; i<pTab->nCol; i++){
+ if( aXRef[i]>=0 ){
+ pExpr = sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr);
+ }else{
+ pExpr = sqlite3CreateIdExpr(pParse, pTab->aCol[i].zName);
+ }
+ pEList = sqlite3ExprListAppend(pParse, pEList, pExpr, 0);
+ }
+ pSelect = sqlite3SelectNew(pParse, pEList, pSrc, pWhere, 0, 0, 0, 0, 0, 0);
+
+ /* Create the ephemeral table into which the update results will
+ ** be stored.
+ */
+ assert( v );
+ ephemTab = pParse->nTab++;
+ sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));
+
+ /* fill the ephemeral table
+ */
+ sqlite3SelectDestInit(&dest, SRT_Table, ephemTab);
+ sqlite3Select(pParse, pSelect, &dest, 0, 0, 0);
+
+ /* Generate code to scan the ephemeral table and call VUpdate. */
+ iReg = ++pParse->nMem;
+ pParse->nMem += pTab->nCol+1;
+ sqlite3VdbeAddOp2(v, OP_Rewind, ephemTab, 0);
+ addr = sqlite3VdbeCurrentAddr(v);
+ sqlite3VdbeAddOp3(v, OP_Column, ephemTab, 0, iReg);
+ sqlite3VdbeAddOp3(v, OP_Column, ephemTab, (pRowid?1:0), iReg+1);
+ for(i=0; i<pTab->nCol; i++){
+ sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i+1+(pRowid!=0), iReg+2+i);
+ }
+ sqlite3VtabMakeWritable(pParse, pTab);
+ sqlite3VdbeAddOp4(v, OP_VUpdate, 0, pTab->nCol+2, iReg, pVtab, P4_VTAB);
+ sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr);
+ sqlite3VdbeJumpHere(v, addr-1);
+ sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);
+
+ /* Cleanup */
+ sqlite3SelectDelete(db, pSelect);
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/* Make sure "isView" gets undefined in case this file becomes part of
+** the amalgamation - so that subsequent files do not see isView as a
+** macro. */
+#undef isView