SQLite-PPL/src/delete.c at master · FlashSQL/SQLite-PPL · GitHub

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** 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

** in order to generate code for DELETE FROM statements.

#include "sqliteInt.h"

** While a SrcList can in general represent multiple tables and subqueries

** (as in the FROM clause of a SELECT statement) in this case it contains

** the name of a single table, as one might find in an INSERT, DELETE,

** or UPDATE statement. Look up that table in the symbol table and

** return a pointer. Set an error message and return NULL if the table

** name is not found or if any other error occurs.

** The following fields are initialized appropriate in pSrc:

** pSrc->a[0].pTab Pointer to the Table object

** pSrc->a[0].pIndex Pointer to the INDEXED BY index, if there is one

Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){

struct SrcList_item *pItem = pSrc->a;

Table *pTab;

assert( pItem && pSrc->nSrc==1 );

pTab = sqlite3LocateTableItem(pParse, 0, pItem);

sqlite3DeleteTable(pParse->db, pItem->pTab);

pItem->pTab = pTab;

if( pTab ){

pTab->nRef++;

}

if( sqlite3IndexedByLookup(pParse, pItem) ){

pTab = 0;

}

return pTab;

}

** Check to make sure the given table is writable. If it is not

** writable, generate an error message and return 1. If it is

** writable return 0;

int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){

/* A table is not writable under the following circumstances:

** 1) It is a virtual table and no implementation of the xUpdate method

** has been provided, or

** 2) It is a system table (i.e. sqlite_master), this call is not

** part of a nested parse and writable_schema pragma has not

** been specified.

** In either case leave an error message in pParse and return non-zero.

if( ( IsVirtual(pTab)

&& sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0 )

|| ( (pTab->tabFlags & TF_Readonly)!=0

&& (pParse->db->flags & SQLITE_WriteSchema)==0

&& pParse->nested==0 )

){

sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);

return 1;

}

#ifndef SQLITE_OMIT_VIEW

if( !viewOk && pTab->pSelect ){

sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);

return 1;

}

#endif

return 0;

}

#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)

** Evaluate a view and store its result in an ephemeral table. The

** pWhere argument is an optional WHERE clause that restricts the

** set of rows in the view that are to be added to the ephemeral table.

void sqlite3MaterializeView(

Parse *pParse, /* Parsing context */

Table *pView, /* View definition */

Expr *pWhere, /* Optional WHERE clause to be added */

int iCur /* Cursor number for ephemeral table */

){

SelectDest dest;

Select *pSel;

SrcList *pFrom;

sqlite3 *db = pParse->db;

int iDb = sqlite3SchemaToIndex(db, pView->pSchema);

pWhere = sqlite3ExprDup(db, pWhere, 0);

pFrom = sqlite3SrcListAppend(db, 0, 0, 0);

if( pFrom ){

assert( pFrom->nSrc==1 );

pFrom->a[0].zName = sqlite3DbStrDup(db, pView->zName);

pFrom->a[0].zDatabase = sqlite3DbStrDup(db, db->aDb[iDb].zName);

assert( pFrom->a[0].pOn==0 );

assert( pFrom->a[0].pUsing==0 );

}

pSel = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, 0,

SF_IncludeHidden, 0, 0);

sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);

sqlite3Select(pParse, pSel, &dest);

sqlite3SelectDelete(db, pSel);

}

#endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */

#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)

** Generate an expression tree to implement the WHERE, ORDER BY,

** and LIMIT/OFFSET portion of DELETE and UPDATE statements.

** DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;

** \__________________________/

** pLimitWhere (pInClause)

Expr *sqlite3LimitWhere(

Parse *pParse, /* The parser context */

SrcList *pSrc, /* the FROM clause -- which tables to scan */

Expr *pWhere, /* The WHERE clause. May be null */

ExprList *pOrderBy, /* The ORDER BY clause. May be null */

Expr *pLimit, /* The LIMIT clause. May be null */

Expr *pOffset, /* The OFFSET clause. May be null */

char *zStmtType /* Either DELETE or UPDATE. For err msgs. */

){

Expr *pWhereRowid = NULL; /* WHERE rowid .. */

Expr *pInClause = NULL; /* WHERE rowid IN ( select ) */

Expr *pSelectRowid = NULL; /* SELECT rowid ... */

ExprList *pEList = NULL; /* Expression list contaning only pSelectRowid */

SrcList *pSelectSrc = NULL; /* SELECT rowid FROM x ... (dup of pSrc) */

Select *pSelect = NULL; /* Complete SELECT tree */

/* Check that there isn't an ORDER BY without a LIMIT clause.

if( pOrderBy && (pLimit == 0) ) {

sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);

goto limit_where_cleanup;

}

/* We only need to generate a select expression if there

** is a limit/offset term to enforce.

if( pLimit == 0 ) {

/* if pLimit is null, pOffset will always be null as well. */

assert( pOffset == 0 );

return pWhere;

}

/* Generate a select expression tree to enforce the limit/offset

** term for the DELETE or UPDATE statement. For example:

** DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1

** becomes:

** DELETE FROM table_a WHERE rowid IN (

** SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1

** );

pSelectRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);

if( pSelectRowid == 0 ) goto limit_where_cleanup;

pEList = sqlite3ExprListAppend(pParse, 0, pSelectRowid);

if( pEList == 0 ) goto limit_where_cleanup;

/* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree

** and the SELECT subtree. */

pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc, 0);

if( pSelectSrc == 0 ) {

sqlite3ExprListDelete(pParse->db, pEList);

goto limit_where_cleanup;

}

/* generate the SELECT expression tree. */

pSelect = sqlite3SelectNew(pParse,pEList,pSelectSrc,pWhere,0,0,

pOrderBy,0,pLimit,pOffset);

if( pSelect == 0 ) return 0;

/* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */

pWhereRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);

pInClause = pWhereRowid ? sqlite3PExpr(pParse, TK_IN, pWhereRowid, 0, 0) : 0;

sqlite3PExprAddSelect(pParse, pInClause, pSelect);

return pInClause;

limit_where_cleanup:

sqlite3ExprDelete(pParse->db, pWhere);

sqlite3ExprListDelete(pParse->db, pOrderBy);

sqlite3ExprDelete(pParse->db, pLimit);

sqlite3ExprDelete(pParse->db, pOffset);

return 0;

}

#endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) */

/* && !defined(SQLITE_OMIT_SUBQUERY) */

** Generate code for a DELETE FROM statement.

** DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;

** \________/ \________________/

** pTabList pWhere

void sqlite3DeleteFrom(

Parse *pParse, /* The parser context */

SrcList *pTabList, /* The table from which we should delete things */

Expr *pWhere /* The WHERE clause. May be null */

){

Vdbe *v; /* The virtual database engine */

Table *pTab; /* The table from which records will be deleted */

const char *zDb; /* Name of database holding pTab */

int i; /* Loop counter */

WhereInfo *pWInfo; /* Information about the WHERE clause */

Index *pIdx; /* For looping over indices of the table */

int iTabCur; /* Cursor number for the table */

int iDataCur = 0; /* VDBE cursor for the canonical data source */

int iIdxCur = 0; /* Cursor number of the first index */

int nIdx; /* Number of indices */

sqlite3 *db; /* Main database structure */

AuthContext sContext; /* Authorization context */

NameContext sNC; /* Name context to resolve expressions in */

int iDb; /* Database number */

int memCnt = -1; /* Memory cell used for change counting */

int rcauth; /* Value returned by authorization callback */

int eOnePass; /* ONEPASS_OFF or _SINGLE or _MULTI */

int aiCurOnePass[2]; /* The write cursors opened by WHERE_ONEPASS */

u8 *aToOpen = 0; /* Open cursor iTabCur+j if aToOpen[j] is true */

Index *pPk; /* The PRIMARY KEY index on the table */

int iPk = 0; /* First of nPk registers holding PRIMARY KEY value */

i16 nPk = 1; /* Number of columns in the PRIMARY KEY */

int iKey; /* Memory cell holding key of row to be deleted */

i16 nKey; /* Number of memory cells in the row key */

int iEphCur = 0; /* Ephemeral table holding all primary key values */

int iRowSet = 0; /* Register for rowset of rows to delete */

int addrBypass = 0; /* Address of jump over the delete logic */

int addrLoop = 0; /* Top of the delete loop */

int addrEphOpen = 0; /* Instruction to open the Ephemeral table */

int bComplex; /* True if there are triggers or FKs or

** subqueries in the WHERE clause */

#ifndef SQLITE_OMIT_TRIGGER

int isView; /* True if attempting to delete from a view */

Trigger *pTrigger; /* List of table triggers, if required */

#endif

memset(&sContext, 0, sizeof(sContext));

db = pParse->db;

if( pParse->nErr || db->mallocFailed ){

goto delete_from_cleanup;

}

assert( pTabList->nSrc==1 );

/* Locate the table which we want to delete. This table has to be

** put in an SrcList structure because some of the subroutines we

** will be calling are designed to work with multiple tables and expect

** an SrcList* parameter instead of just a Table* parameter.

pTab = sqlite3SrcListLookup(pParse, pTabList);

if( pTab==0 ) goto delete_from_cleanup;

/* Figure out if we have any triggers and if the table being

** deleted from is a view

#ifndef SQLITE_OMIT_TRIGGER

pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);

isView = pTab->pSelect!=0;

bComplex = pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0);

#else

# define pTrigger 0

# define isView 0

#endif

#ifdef SQLITE_OMIT_VIEW

# undef isView

# define isView 0

#endif

/* If pTab is really a view, make sure it has been initialized.

if( sqlite3ViewGetColumnNames(pParse, pTab) ){

goto delete_from_cleanup;

}

if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){

goto delete_from_cleanup;

}

iDb = sqlite3SchemaToIndex(db, pTab->pSchema);

assert( iDb<db->nDb );

zDb = db->aDb[iDb].zName;

rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb);

assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );

if( rcauth==SQLITE_DENY ){

goto delete_from_cleanup;

}

assert(!isView || pTrigger);

/* Assign cursor numbers to the table and all its indices.

assert( pTabList->nSrc==1 );

iTabCur = pTabList->a[0].iCursor = pParse->nTab++;

for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){

pParse->nTab++;

}

/* Start the view context

if( isView ){

sqlite3AuthContextPush(pParse, &sContext, pTab->zName);

}

/* Begin generating code.

v = sqlite3GetVdbe(pParse);

if( v==0 ){

goto delete_from_cleanup;

}

if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);

sqlite3BeginWriteOperation(pParse, 1, iDb);

/* If we are trying to delete from a view, realize that view into

** an ephemeral table.

#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)

if( isView ){

sqlite3MaterializeView(pParse, pTab, pWhere, iTabCur);

iDataCur = iIdxCur = iTabCur;

}

#endif

/* Resolve the column names in the WHERE clause.

memset(&sNC, 0, sizeof(sNC));

sNC.pParse = pParse;

sNC.pSrcList = pTabList;

if( sqlite3ResolveExprNames(&sNC, pWhere) ){

goto delete_from_cleanup;

}

/* Initialize the counter of the number of rows deleted, if

** we are counting rows.

if( db->flags & SQLITE_CountRows ){

memCnt = ++pParse->nMem;

sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);

}

#ifndef SQLITE_OMIT_TRUNCATE_OPTIMIZATION

/* Special case: A DELETE without a WHERE clause deletes everything.

** It is easier just to erase the whole table. Prior to version 3.6.5,

** this optimization caused the row change count (the value returned by

** API function sqlite3_count_changes) to be set incorrectly. */

if( rcauth==SQLITE_OK

&& pWhere==0

&& !bComplex

&& !IsVirtual(pTab)

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK

&& db->xPreUpdateCallback==0

#endif

){

assert( !isView );

sqlite3TableLock(pParse, iDb, pTab->tnum, 1, pTab->zName);

if( HasRowid(pTab) ){

sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt,

pTab->zName, P4_STATIC);

}

for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){

assert( pIdx->pSchema==pTab->pSchema );

sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);

}

}else

#endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */

{

u16 wcf = WHERE_ONEPASS_DESIRED|WHERE_DUPLICATES_OK|WHERE_SEEK_TABLE;

if( sNC.ncFlags & NC_VarSelect ) bComplex = 1;

wcf |= (bComplex ? 0 : WHERE_ONEPASS_MULTIROW);

if( HasRowid(pTab) ){

/* For a rowid table, initialize the RowSet to an empty set */

pPk = 0;

nPk = 1;

iRowSet = ++pParse->nMem;

sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);

}else{

/* For a WITHOUT ROWID table, create an ephemeral table used to

** hold all primary keys for rows to be deleted. */

pPk = sqlite3PrimaryKeyIndex(pTab);

assert( pPk!=0 );

nPk = pPk->nKeyCol;

iPk = pParse->nMem+1;

pParse->nMem += nPk;

iEphCur = pParse->nTab++;

addrEphOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEphCur, nPk);

sqlite3VdbeSetP4KeyInfo(pParse, pPk);

}

/* Construct a query to find the rowid or primary key for every row

** to be deleted, based on the WHERE clause. Set variable eOnePass

** to indicate the strategy used to implement this delete:

** ONEPASS_OFF: Two-pass approach - use a FIFO for rowids/PK values.

** ONEPASS_SINGLE: One-pass approach - at most one row deleted.

** ONEPASS_MULTI: One-pass approach - any number of rows may be deleted.

pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0, wcf, iTabCur+1);

if( pWInfo==0 ) goto delete_from_cleanup;

eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);

assert( IsVirtual(pTab)==0 || eOnePass!=ONEPASS_MULTI );

assert( IsVirtual(pTab) || bComplex || eOnePass!=ONEPASS_OFF );

/* Keep track of the number of rows to be deleted */

if( db->flags & SQLITE_CountRows ){

sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);

}

/* Extract the rowid or primary key for the current row */

if( pPk ){

for(i=0; i<nPk; i++){

assert( pPk->aiColumn[i]>=0 );

sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur,

pPk->aiColumn[i], iPk+i);

}

iKey = iPk;

}else{

iKey = pParse->nMem + 1;

iKey = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iTabCur, iKey, 0);

if( iKey>pParse->nMem ) pParse->nMem = iKey;

}

if( eOnePass!=ONEPASS_OFF ){

/* For ONEPASS, no need to store the rowid/primary-key. There is only

** one, so just keep it in its register(s) and fall through to the

** delete code. */

nKey = nPk; /* OP_Found will use an unpacked key */

aToOpen = sqlite3DbMallocRawNN(db, nIdx+2);

if( aToOpen==0 ){

sqlite3WhereEnd(pWInfo);

goto delete_from_cleanup;

}

memset(aToOpen, 1, nIdx+1);

aToOpen[nIdx+1] = 0;

if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iTabCur] = 0;

if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iTabCur] = 0;

if( addrEphOpen ) sqlite3VdbeChangeToNoop(v, addrEphOpen);

}else{

if( pPk ){

/* Add the PK key for this row to the temporary table */

iKey = ++pParse->nMem;

nKey = 0; /* Zero tells OP_Found to use a composite key */

sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, iKey,

sqlite3IndexAffinityStr(pParse->db, pPk), nPk);

sqlite3VdbeAddOp2(v, OP_IdxInsert, iEphCur, iKey);

}else{

/* Add the rowid of the row to be deleted to the RowSet */

nKey = 1; /* OP_Seek always uses a single rowid */

sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iKey);

}

/* If this DELETE cannot use the ONEPASS strategy, this is the

** end of the WHERE loop */

if( eOnePass!=ONEPASS_OFF ){

addrBypass = sqlite3VdbeMakeLabel(v);

}else{

sqlite3WhereEnd(pWInfo);

}

/* Unless this is a view, open cursors for the table we are

** deleting from and all its indices. If this is a view, then the

** only effect this statement has is to fire the INSTEAD OF

** triggers.

if( !isView ){

int iAddrOnce = 0;

if( eOnePass==ONEPASS_MULTI ){

iAddrOnce = sqlite3CodeOnce(pParse); VdbeCoverage(v);

}

testcase( IsVirtual(pTab) );

sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, OPFLAG_FORDELETE,

iTabCur, aToOpen, &iDataCur, &iIdxCur);

assert( pPk || IsVirtual(pTab) || iDataCur==iTabCur );

assert( pPk || IsVirtual(pTab) || iIdxCur==iDataCur+1 );

if( eOnePass==ONEPASS_MULTI ) sqlite3VdbeJumpHere(v, iAddrOnce);

}

/* Set up a loop over the rowids/primary-keys that were found in the

** where-clause loop above.

if( eOnePass!=ONEPASS_OFF ){

assert( nKey==nPk ); /* OP_Found will use an unpacked key */

if( !IsVirtual(pTab) && aToOpen[iDataCur-iTabCur] ){

assert( pPk!=0 || pTab->pSelect!=0 );

sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, addrBypass, iKey, nKey);

VdbeCoverage(v);

}

}else if( pPk ){

addrLoop = sqlite3VdbeAddOp1(v, OP_Rewind, iEphCur); VdbeCoverage(v);

sqlite3VdbeAddOp2(v, OP_RowKey, iEphCur, iKey);

assert( nKey==0 ); /* OP_Found will use a composite key */

}else{

addrLoop = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, 0, iKey);

VdbeCoverage(v);

assert( nKey==1 );

}

/* Delete the row */

#ifndef SQLITE_OMIT_VIRTUALTABLE

if( IsVirtual(pTab) ){

const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);

sqlite3VtabMakeWritable(pParse, pTab);

sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iKey, pVTab, P4_VTAB);

sqlite3VdbeChangeP5(v, OE_Abort);

assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );

sqlite3MayAbort(pParse);

if( eOnePass==ONEPASS_SINGLE && sqlite3IsToplevel(pParse) ){

pParse->isMultiWrite = 0;

}

}else

#endif

{

int count = (pParse->nested==0); /* True to count changes */

int iIdxNoSeek = -1;

if( bComplex==0 && aiCurOnePass[1]!=iDataCur ){

iIdxNoSeek = aiCurOnePass[1];

}

sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,

iKey, nKey, count, OE_Default, eOnePass, iIdxNoSeek);

}

/* End of the loop over all rowids/primary-keys. */

if( eOnePass!=ONEPASS_OFF ){

sqlite3VdbeResolveLabel(v, addrBypass);

sqlite3WhereEnd(pWInfo);

}else if( pPk ){

sqlite3VdbeAddOp2(v, OP_Next, iEphCur, addrLoop+1); VdbeCoverage(v);

sqlite3VdbeJumpHere(v, addrLoop);

}else{

sqlite3VdbeGoto(v, addrLoop);

sqlite3VdbeJumpHere(v, addrLoop);

}

/* Close the cursors open on the table and its indexes. */

if( !isView && !IsVirtual(pTab) ){

if( !pPk ) sqlite3VdbeAddOp1(v, OP_Close, iDataCur);

for(i=0, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){

sqlite3VdbeAddOp1(v, OP_Close, iIdxCur + i);

}

} /* End non-truncate path */

/* Update the sqlite_sequence table by storing the content of the

** maximum rowid counter values recorded while inserting into

** autoincrement tables.

if( pParse->nested==0 && pParse->pTriggerTab==0 ){

sqlite3AutoincrementEnd(pParse);

}

/* Return the number of rows that were deleted. If this routine is

** generating code because of a call to sqlite3NestedParse(), do not

** invoke the callback function.

if( (db->flags&SQLITE_CountRows) && !pParse->nested && !pParse->pTriggerTab ){

sqlite3VdbeAddOp2(v, OP_ResultRow, memCnt, 1);

sqlite3VdbeSetNumCols(v, 1);

sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);

}

delete_from_cleanup:

sqlite3AuthContextPop(&sContext);

sqlite3SrcListDelete(db, pTabList);

sqlite3ExprDelete(db, pWhere);

sqlite3DbFree(db, aToOpen);

return;

}

/* Make sure "isView" and other macros defined above are undefined. Otherwise

** they may interfere with compilation of other functions in this file

** (or in another file, if this file becomes part of the amalgamation). */

#ifdef isView

#undef isView

#endif

#ifdef pTrigger

#undef pTrigger

#endif

** This routine generates VDBE code that causes a single row of a

** single table to be deleted. Both the original table entry and

** all indices are removed.

** Preconditions:

** 1. iDataCur is an open cursor on the btree that is the canonical data

** store for the table. (This will be either the table itself,

** in the case of a rowid table, or the PRIMARY KEY index in the case

** of a WITHOUT ROWID table.)

** 2. Read/write cursors for all indices of pTab must be open as

** cursor number iIdxCur+i for the i-th index.

** 3. The primary key for the row to be deleted must be stored in a

** sequence of nPk memory cells starting at iPk. If nPk==0 that means

** that a search record formed from OP_MakeRecord is contained in the

** single memory location iPk.

** eMode:

** Parameter eMode may be passed either ONEPASS_OFF (0), ONEPASS_SINGLE, or

** ONEPASS_MULTI. If eMode is not ONEPASS_OFF, then the cursor

** iDataCur already points to the row to delete. If eMode is ONEPASS_OFF

** then this function must seek iDataCur to the entry identified by iPk

** and nPk before reading from it.

** If eMode is ONEPASS_MULTI, then this call is being made as part

** of a ONEPASS delete that affects multiple rows. In this case, if

** iIdxNoSeek is a valid cursor number (>=0), then its position should

** be preserved following the delete operation. Or, if iIdxNoSeek is not

** a valid cursor number, the position of iDataCur should be preserved

** instead.

** iIdxNoSeek:

** If iIdxNoSeek is a valid cursor number (>=0), then it identifies an

** index cursor (from within array of cursors starting at iIdxCur) that

** already points to the index entry to be deleted.

void sqlite3GenerateRowDelete(

Parse *pParse, /* Parsing context */

Table *pTab, /* Table containing the row to be deleted */

Trigger *pTrigger, /* List of triggers to (potentially) fire */

int iDataCur, /* Cursor from which column data is extracted */

int iIdxCur, /* First index cursor */

int iPk, /* First memory cell containing the PRIMARY KEY */

i16 nPk, /* Number of PRIMARY KEY memory cells */

u8 count, /* If non-zero, increment the row change counter */

u8 onconf, /* Default ON CONFLICT policy for triggers */

u8 eMode, /* ONEPASS_OFF, _SINGLE, or _MULTI. See above */

int iIdxNoSeek /* Cursor number of cursor that does not need seeking */

){

Vdbe *v = pParse->pVdbe; /* Vdbe */

int iOld = 0; /* First register in OLD.* array */

int iLabel; /* Label resolved to end of generated code */

u8 opSeek; /* Seek opcode */

/* Vdbe is guaranteed to have been allocated by this stage. */

assert( v );

VdbeModuleComment((v, "BEGIN: GenRowDel(%d,%d,%d,%d)",

iDataCur, iIdxCur, iPk, (int)nPk));

/* Seek cursor iCur to the row to delete. If this row no longer exists

** (this can happen if a trigger program has already deleted it), do

** not attempt to delete it or fire any DELETE triggers. */

iLabel = sqlite3VdbeMakeLabel(v);

opSeek = HasRowid(pTab) ? OP_NotExists : OP_NotFound;

if( eMode==ONEPASS_OFF ){

sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);

VdbeCoverageIf(v, opSeek==OP_NotExists);

VdbeCoverageIf(v, opSeek==OP_NotFound);

}

/* If there are any triggers to fire, allocate a range of registers to

** use for the old.* references in the triggers. */

if( sqlite3FkRequired(pParse, pTab, 0, 0) || pTrigger ){

u32 mask; /* Mask of OLD.* columns in use */

int iCol; /* Iterator used while populating OLD.* */

int addrStart; /* Start of BEFORE trigger programs */

/* TODO: Could use temporary registers here. Also could attempt to

** avoid copying the contents of the rowid register. */

mask = sqlite3TriggerColmask(

pParse, pTrigger, 0, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onconf

);

mask |= sqlite3FkOldmask(pParse, pTab);

iOld = pParse->nMem+1;

pParse->nMem += (1 + pTab->nCol);

/* Populate the OLD.* pseudo-table register array. These values will be

** used by any BEFORE and AFTER triggers that exist. */

sqlite3VdbeAddOp2(v, OP_Copy, iPk, iOld);

for(iCol=0; iCol<pTab->nCol; iCol++){

testcase( mask!=0xffffffff && iCol==31 );

testcase( mask!=0xffffffff && iCol==32 );

if( mask==0xffffffff || (iCol<=31 && (mask & MASKBIT32(iCol))!=0) ){

sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, iCol, iOld+iCol+1);

}

/* Invoke BEFORE DELETE trigger programs. */

addrStart = sqlite3VdbeCurrentAddr(v);

sqlite3CodeRowTrigger(pParse, pTrigger,

TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel

);

/* If any BEFORE triggers were coded, then seek the cursor to the

** row to be deleted again. It may be that the BEFORE triggers moved

** the cursor or of already deleted the row that the cursor was

** pointing to.

if( addrStart<sqlite3VdbeCurrentAddr(v) ){

sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);

VdbeCoverageIf(v, opSeek==OP_NotExists);

VdbeCoverageIf(v, opSeek==OP_NotFound);

}

/* Do FK processing. This call checks that any FK constraints that

** refer to this table (i.e. constraints attached to other tables)

** are not violated by deleting this row. */

sqlite3FkCheck(pParse, pTab, iOld, 0, 0, 0);

}

/* Delete the index and table entries. Skip this step if pTab is really

** a view (in which case the only effect of the DELETE statement is to

** fire the INSTEAD OF triggers).

** If variable 'count' is non-zero, then this OP_Delete instruction should

** invoke the update-hook. The pre-update-hook, on the other hand should

** be invoked unless table pTab is a system table. The difference is that

** the update-hook is not invoked for rows removed by REPLACE, but the

** pre-update-hook is.

if( pTab->pSelect==0 ){

u8 p5 = 0;

sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,iIdxNoSeek);

sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, (count?OPFLAG_NCHANGE:0));

sqlite3VdbeChangeP4(v, -1, (char*)pTab, P4_TABLE);

if( eMode!=ONEPASS_OFF ){

sqlite3VdbeChangeP5(v, OPFLAG_AUXDELETE);

}

if( iIdxNoSeek>=0 ){

sqlite3VdbeAddOp1(v, OP_Delete, iIdxNoSeek);

}

if( eMode==ONEPASS_MULTI ) p5 |= OPFLAG_SAVEPOSITION;

sqlite3VdbeChangeP5(v, p5);

}

/* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to

** handle rows (possibly in other tables) that refer via a foreign key

** to the row just deleted. */

sqlite3FkActions(pParse, pTab, 0, iOld, 0, 0);

/* Invoke AFTER DELETE trigger programs. */

sqlite3CodeRowTrigger(pParse, pTrigger,

TK_DELETE, 0, TRIGGER_AFTER, pTab, iOld, onconf, iLabel

);

/* Jump here if the row had already been deleted before any BEFORE

** trigger programs were invoked. Or if a trigger program throws a

** RAISE(IGNORE) exception. */

sqlite3VdbeResolveLabel(v, iLabel);

VdbeModuleComment((v, "END: GenRowDel()"));

}

** This routine generates VDBE code that causes the deletion of all

** index entries associated with a single row of a single table, pTab

** Preconditions:

** 1. A read/write cursor "iDataCur" must be open on the canonical storage

** btree for the table pTab. (This will be either the table itself

** for rowid tables or to the primary key index for WITHOUT ROWID

** tables.)

** 2. Read/write cursors for all indices of pTab must be open as

** cursor number iIdxCur+i for the i-th index. (The pTab->pIndex

** index is the 0-th index.)

** 3. The "iDataCur" cursor must be already be positioned on the row

** that is to be deleted.

void sqlite3GenerateRowIndexDelete(

Parse *pParse, /* Parsing and code generating context */

Table *pTab, /* Table containing the row to be deleted */

int iDataCur, /* Cursor of table holding data. */

int iIdxCur, /* First index cursor */

int *aRegIdx, /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */

int iIdxNoSeek /* Do not delete from this cursor */

){

int i; /* Index loop counter */

int r1 = -1; /* Register holding an index key */

int iPartIdxLabel; /* Jump destination for skipping partial index entries */

Index *pIdx; /* Current index */

Index *pPrior = 0; /* Prior index */

Vdbe *v; /* The prepared statement under construction */

Index *pPk; /* PRIMARY KEY index, or NULL for rowid tables */

v = pParse->pVdbe;

pPk = HasRowid(pTab) ? 0 : sqlite3PrimaryKeyIndex(pTab);

for(i=0, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){

assert( iIdxCur+i!=iDataCur || pPk==pIdx );

if( aRegIdx!=0 && aRegIdx[i]==0 ) continue;

if( pIdx==pPk ) continue;

if( iIdxCur+i==iIdxNoSeek ) continue;

VdbeModuleComment((v, "GenRowIdxDel for %s", pIdx->zName));

r1 = sqlite3GenerateIndexKey(pParse, pIdx, iDataCur, 0, 1,

&iPartIdxLabel, pPrior, r1);

sqlite3VdbeAddOp3(v, OP_IdxDelete, iIdxCur+i, r1,

pIdx->uniqNotNull ? pIdx->nKeyCol : pIdx->nColumn);

sqlite3ResolvePartIdxLabel(pParse, iPartIdxLabel);

pPrior = pIdx;

}

** Generate code that will assemble an index key and stores it in register

** regOut. The key with be for index pIdx which is an index on pTab.

** iCur is the index of a cursor open on the pTab table and pointing to

** the entry that needs indexing. If pTab is a WITHOUT ROWID table, then

** iCur must be the cursor of the PRIMARY KEY index.

** Return a register number which is the first in a block of

** registers that holds the elements of the index key. The

** block of registers has already been deallocated by the time

** this routine returns.

** If *piPartIdxLabel is not NULL, fill it in with a label and jump

** to that label if pIdx is a partial index that should be skipped.

** The label should be resolved using sqlite3ResolvePartIdxLabel().

** A partial index should be skipped if its WHERE clause evaluates

** to false or null. If pIdx is not a partial index, *piPartIdxLabel

** will be set to zero which is an empty label that is ignored by

** sqlite3ResolvePartIdxLabel().

** The pPrior and regPrior parameters are used to implement a cache to

** avoid unnecessary register loads. If pPrior is not NULL, then it is

** a pointer to a different index for which an index key has just been

** computed into register regPrior. If the current pIdx index is generating

** its key into the same sequence of registers and if pPrior and pIdx share

** a column in common, then the register corresponding to that column already

** holds the correct value and the loading of that register is skipped.

** This optimization is helpful when doing a DELETE or an INTEGRITY_CHECK

** on a table with multiple indices, and especially with the ROWID or

** PRIMARY KEY columns of the index.

int sqlite3GenerateIndexKey(

Parse *pParse, /* Parsing context */

Index *pIdx, /* The index for which to generate a key */

int iDataCur, /* Cursor number from which to take column data */

int regOut, /* Put the new key into this register if not 0 */

int prefixOnly, /* Compute only a unique prefix of the key */

int *piPartIdxLabel, /* OUT: Jump to this label to skip partial index */

Index *pPrior, /* Previously generated index key */

int regPrior /* Register holding previous generated key */

){

Vdbe *v = pParse->pVdbe;

int j;

int regBase;

int nCol;

if( piPartIdxLabel ){

if( pIdx->pPartIdxWhere ){

*piPartIdxLabel = sqlite3VdbeMakeLabel(v);

pParse->iSelfTab = iDataCur;

sqlite3ExprCachePush(pParse);

sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, *piPartIdxLabel,

SQLITE_JUMPIFNULL);

}else{

*piPartIdxLabel = 0;

}

nCol = (prefixOnly && pIdx->uniqNotNull) ? pIdx->nKeyCol : pIdx->nColumn;

regBase = sqlite3GetTempRange(pParse, nCol);

if( pPrior && (regBase!=regPrior || pPrior->pPartIdxWhere) ) pPrior = 0;

for(j=0; j<nCol; j++){

if( pPrior

&& pPrior->aiColumn[j]==pIdx->aiColumn[j]

&& pPrior->aiColumn[j]!=XN_EXPR

){

/* This column was already computed by the previous index */

continue;

}

sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iDataCur, j, regBase+j);

/* If the column affinity is REAL but the number is an integer, then it

** might be stored in the table as an integer (using a compact

** representation) then converted to REAL by an OP_RealAffinity opcode.

** But we are getting ready to store this value back into an index, where

** it should be converted by to INTEGER again. So omit the OP_RealAffinity

** opcode if it is present */

sqlite3VdbeDeletePriorOpcode(v, OP_RealAffinity);

}

if( regOut ){

sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regOut);

}

sqlite3ReleaseTempRange(pParse, regBase, nCol);

return regBase;

}

** If a prior call to sqlite3GenerateIndexKey() generated a jump-over label

** because it was a partial index, then this routine should be called to

** resolve that label.

void sqlite3ResolvePartIdxLabel(Parse *pParse, int iLabel){

if( iLabel ){

sqlite3VdbeResolveLabel(pParse->pVdbe, iLabel);

sqlite3ExprCachePop(pParse);

}

SQLite-PPL/src/delete.c at master · FlashSQL/SQLite-PPL · GitHub

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