vdbe
了解了Vdbe数据结构，我们再来看看我们平时常用的API是如何与VDBE交换数据的。通常我们要执行一个语句，会执行如下几个步骤。 1.调用sqlite3_prepare_来编译生成指令流，返回一个sqlite3_stmt对象，其实这个对象就是vdbe对象。 2.调用sqlite3_bind_来将参数传递给vdbe 3.调用sqlite3_step进行执行，这时候会启动虚拟机执行一条条指令，直到遇到中断或者停止指令为止 4.调用sqlite3_column_*来获取上一步准备好的结果集 5.调用sqlite3_finalize,销毁vdbe对象，结束这次执行。 此外我们还可能用到sqlite3_reset接口，这个接口将指令流回退到第一条指令，用户可以调用sqlite3_step重新执行。有关API的详细说明，可以参考文件vdbeapi.c。
sqlite3_prepare会解释sql，并且生成一个sqlite3_stmt对象，一个stmt对象存储着一条sql语言的全部字节码。 sqlite3_step->sqlite3VdbeExec 部分源码
/*
** Execute as much of a VDBE program as we can.
** This is the core of sqlite3_step().
*/
int sqlite3VdbeExec(
Vdbe *p /* The VDBE */
){
Op *aOp = p->aOp; /* Copy of p->aOp */
Op *pOp = aOp; /* Current operation */
#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
Op *pOrigOp; /* Value of pOp at the top of the loop */
#endif
#ifdef SQLITE_DEBUG
int nExtraDelete = 0; /* Verifies FORDELETE and AUXDELETE flags */
#endif
int rc = SQLITE_OK; /* Value to return */
sqlite3 *db = p->db; /* The database */
u8 resetSchemaOnFault = 0; /* Reset schema after an error if positive */
u8 encoding = ENC(db); /* The database encoding */
int iCompare = 0; /* Result of last comparison */
unsigned nVmStep = 0; /* Number of virtual machine steps */
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
unsigned nProgressLimit; /* Invoke xProgress() when nVmStep reaches this */
#endif
Mem *aMem = p->aMem; /* Copy of p->aMem */
Mem *pIn1 = 0; /* 1st input operand */
Mem *pIn2 = 0; /* 2nd input operand */
Mem *pIn3 = 0; /* 3rd input operand */
Mem *pOut = 0; /* Output operand */
...
for(pOp=&aOp[p->pc]; 1; pOp++){
...
nVmStep++;
switch( pOp->opcode ){
case OP_Gosub:
break;
...
}
op操作码
/* Automatically generated. Do not edit */
/* See the tool/mkopcodeh.tcl script for details */
#define OP_Savepoint 0
#define OP_AutoCommit 1
#define OP_Transaction 2
#define OP_SorterNext 3 /* jump */
#define OP_Prev 4 /* jump */
#define OP_Next 5 /* jump */
#define OP_Checkpoint 6
#define OP_JournalMode 7
#define OP_Vacuum 8
#define OP_VFilter 9 /* jump, synopsis: iplan=r[P3] zplan='P4' */
#define OP_VUpdate 10 /* synopsis: data=r[P3@P2] */
#define OP_Goto 11 /* jump */
#define OP_Gosub 12 /* jump */
#define OP_InitCoroutine 13 /* jump */
#define OP_Yield 14 /* jump */
#define OP_MustBeInt 15 /* jump */
#define OP_Jump 16 /* jump */
#define OP_Once 17 /* jump */
#define OP_If 18 /* jump */
#define OP_Not 19 /* same as TK_NOT, synopsis: r[P2]= !r[P1] */
#define OP_IfNot 20 /* jump */
#define OP_IfNullRow 21 /* jump, synopsis: if P1.nullRow then r[P3]=NULL, goto P2 */
#define OP_SeekLT 22 /* jump, synopsis: key=r[P3@P4] */
#define OP_SeekLE 23 /* jump, synopsis: key=r[P3@P4] */
#define OP_SeekGE 24 /* jump, synopsis: key=r[P3@P4] */
#define OP_SeekGT 25 /* jump, synopsis: key=r[P3@P4] */
#define OP_IfNoHope 26 /* jump, synopsis: key=r[P3@P4] */
#define OP_NoConflict 27 /* jump, synopsis: key=r[P3@P4] */
#define OP_NotFound 28 /* jump, synopsis: key=r[P3@P4] */
#define OP_Found 29 /* jump, synopsis: key=r[P3@P4] */
#define OP_SeekRowid 30 /* jump, synopsis: intkey=r[P3] */
#define OP_NotExists 31 /* jump, synopsis: intkey=r[P3] */
#define OP_Last 32 /* jump */
#define OP_IfSmaller 33 /* jump */
#define OP_SorterSort 34 /* jump */
#define OP_Sort 35 /* jump */
#define OP_Rewind 36 /* jump */
#define OP_IdxLE 37 /* jump, synopsis: key=r[P3@P4] */
#define OP_IdxGT 38 /* jump, synopsis: key=r[P3@P4] */
#define OP_IdxLT 39 /* jump, synopsis: key=r[P3@P4] */
#define OP_IdxGE 40 /* jump, synopsis: key=r[P3@P4] */
#define OP_RowSetRead 41 /* jump, synopsis: r[P3]=rowset(P1) */
#define OP_RowSetTest 42 /* jump, synopsis: if r[P3] in rowset(P1) goto P2 */
#define OP_Or 43 /* same as TK_OR, synopsis: r[P3]=(r[P1] || r[P2]) */
#define OP_And 44 /* same as TK_AND, synopsis: r[P3]=(r[P1] && r[P2]) */
#define OP_Program 45 /* jump */
#define OP_FkIfZero 46 /* jump, synopsis: if fkctr[P1]==0 goto P2 */
#define OP_IfPos 47 /* jump, synopsis: if r[P1]>0 then r[P1]-=P3, goto P2 */
#define OP_IfNotZero 48 /* jump, synopsis: if r[P1]!=0 then r[P1]--, goto P2 */
#define OP_DecrJumpZero 49 /* jump, synopsis: if (--r[P1])==0 goto P2 */
#define OP_IsNull 50 /* jump, same as TK_ISNULL, synopsis: if r[P1]==NULL goto P2 */
#define OP_NotNull 51 /* jump, same as TK_NOTNULL, synopsis: if r[P1]!=NULL goto P2 */
#define OP_Ne 52 /* jump, same as TK_NE, synopsis: IF r[P3]!=r[P1] */
#define OP_Eq 53 /* jump, same as TK_EQ, synopsis: IF r[P3]==r[P1] */
#define OP_Gt 54 /* jump, same as TK_GT, synopsis: IF r[P3]>r[P1] */
#define OP_Le 55 /* jump, same as TK_LE, synopsis: IF r[P3]<=r[P1] */
#define OP_Lt 56 /* jump, same as TK_LT, synopsis: IF r[P3]<r[P1] */
#define OP_Ge 57 /* jump, same as TK_GE, synopsis: IF r[P3]>=r[P1] */
#define OP_ElseNotEq 58 /* jump, same as TK_ESCAPE */
#define OP_IncrVacuum 59 /* jump */
#define OP_VNext 60 /* jump */
#define OP_Init 61 /* jump, synopsis: Start at P2 */
#define OP_PureFunc0 62
#define OP_Function0 63 /* synopsis: r[P3]=func(r[P2@P5]) */
#define OP_PureFunc 64
#define OP_Function 65 /* synopsis: r[P3]=func(r[P2@P5]) */
#define OP_Return 66
#define OP_EndCoroutine 67
#define OP_HaltIfNull 68 /* synopsis: if r[P3]=null halt */
#define OP_Halt 69
#define OP_Integer 70 /* synopsis: r[P2]=P1 */
#define OP_Int64 71 /* synopsis: r[P2]=P4 */
#define OP_String 72 /* synopsis: r[P2]='P4' (len=P1) */
#define OP_Null 73 /* synopsis: r[P2..P3]=NULL */
#define OP_SoftNull 74 /* synopsis: r[P1]=NULL */
#define OP_Blob 75 /* synopsis: r[P2]=P4 (len=P1) */
#define OP_Variable 76 /* synopsis: r[P2]=parameter(P1,P4) */
#define OP_Move 77 /* synopsis: r[P2@P3]=r[P1@P3] */
#define OP_Copy 78 /* synopsis: r[P2@P3+1]=r[P1@P3+1] */
#define OP_SCopy 79 /* synopsis: r[P2]=r[P1] */
#define OP_IntCopy 80 /* synopsis: r[P2]=r[P1] */
#define OP_ResultRow 81 /* synopsis: output=r[P1@P2] */
#define OP_CollSeq 82
#define OP_AddImm 83 /* synopsis: r[P1]=r[P1]+P2 */
#define OP_RealAffinity 84
#define OP_Cast 85 /* synopsis: affinity(r[P1]) */
#define OP_Permutation 86
#define OP_Compare 87 /* synopsis: r[P1@P3] <-> r[P2@P3] */
#define OP_IsTrue 88 /* synopsis: r[P2] = coalesce(r[P1]==TRUE,P3) ^ P4 */
#define OP_Offset 89 /* synopsis: r[P3] = sqlite_offset(P1) */
#define OP_Column 90 /* synopsis: r[P3]=PX */
#define OP_Affinity 91 /* synopsis: affinity(r[P1@P2]) */
#define OP_MakeRecord 92 /* synopsis: r[P3]=mkrec(r[P1@P2]) */
#define OP_Count 93 /* synopsis: r[P2]=count() */
#define OP_ReadCookie 94
#define OP_SetCookie 95
#define OP_BitAnd 96 /* same as TK_BITAND, synopsis: r[P3]=r[P1]&r[P2] */
#define OP_BitOr 97 /* same as TK_BITOR, synopsis: r[P3]=r[P1]|r[P2] */
#define OP_ShiftLeft 98 /* same as TK_LSHIFT, synopsis: r[P3]=r[P2]<<r[P1] */
#define OP_ShiftRight 99 /* same as TK_RSHIFT, synopsis: r[P3]=r[P2]>>r[P1] */
#define OP_Add 100 /* same as TK_PLUS, synopsis: r[P3]=r[P1]+r[P2] */
#define OP_Subtract 101 /* same as TK_MINUS, synopsis: r[P3]=r[P2]-r[P1] */
#define OP_Multiply 102 /* same as TK_STAR, synopsis: r[P3]=r[P1]*r[P2] */
#define OP_Divide 103 /* same as TK_SLASH, synopsis: r[P3]=r[P2]/r[P1] */
#define OP_Remainder 104 /* same as TK_REM, synopsis: r[P3]=r[P2]%r[P1] */
#define OP_Concat 105 /* same as TK_CONCAT, synopsis: r[P3]=r[P2]+r[P1] */
#define OP_ReopenIdx 106 /* synopsis: root=P2 iDb=P3 */
#define OP_BitNot 107 /* same as TK_BITNOT, synopsis: r[P2]= ~r[P1] */
#define OP_OpenRead 108 /* synopsis: root=P2 iDb=P3 */
#define OP_OpenWrite 109 /* synopsis: root=P2 iDb=P3 */
#define OP_String8 110 /* same as TK_STRING, synopsis: r[P2]='P4' */
#define OP_OpenDup 111
#define OP_OpenAutoindex 112 /* synopsis: nColumn=P2 */
#define OP_OpenEphemeral 113 /* synopsis: nColumn=P2 */
#define OP_SorterOpen 114
#define OP_SequenceTest 115 /* synopsis: if( cursor[P1].ctr++ ) pc = P2 */
#define OP_OpenPseudo 116 /* synopsis: P3 columns in r[P2] */
#define OP_Close 117
#define OP_ColumnsUsed 118
#define OP_SeekHit 119 /* synopsis: seekHit=P2 */
#define OP_Sequence 120 /* synopsis: r[P2]=cursor[P1].ctr++ */
#define OP_NewRowid 121 /* synopsis: r[P2]=rowid */
#define OP_Insert 122 /* synopsis: intkey=r[P3] data=r[P2] */
#define OP_Delete 123
#define OP_ResetCount 124
#define OP_SorterCompare 125 /* synopsis: if key(P1)!=trim(r[P3],P4) goto P2 */
#define OP_SorterData 126 /* synopsis: r[P2]=data */
#define OP_RowData 127 /* synopsis: r[P2]=data */
#define OP_Rowid 128 /* synopsis: r[P2]=rowid */
#define OP_NullRow 129
#define OP_SeekEnd 130
#define OP_SorterInsert 131 /* synopsis: key=r[P2] */
#define OP_IdxInsert 132 /* synopsis: key=r[P2] */
#define OP_IdxDelete 133 /* synopsis: key=r[P2@P3] */
#define OP_DeferredSeek 134 /* synopsis: Move P3 to P1.rowid if needed */
#define OP_IdxRowid 135 /* synopsis: r[P2]=rowid */
#define OP_Destroy 136
#define OP_Clear 137
#define OP_ResetSorter 138
#define OP_CreateBtree 139 /* synopsis: r[P2]=root iDb=P1 flags=P3 */
#define OP_SqlExec 140
#define OP_ParseSchema 141
#define OP_LoadAnalysis 142
#define OP_DropTable 143
#define OP_DropIndex 144
#define OP_Real 145 /* same as TK_FLOAT, synopsis: r[P2]=P4 */
#define OP_DropTrigger 146
#define OP_IntegrityCk 147
#define OP_RowSetAdd 148 /* synopsis: rowset(P1)=r[P2] */
#define OP_Param 149
#define OP_FkCounter 150 /* synopsis: fkctr[P1]+=P2 */
#define OP_MemMax 151 /* synopsis: r[P1]=max(r[P1],r[P2]) */
#define OP_OffsetLimit 152 /* synopsis: if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1) */
#define OP_AggInverse 153 /* synopsis: accum=r[P3] inverse(r[P2@P5]) */
#define OP_AggStep 154 /* synopsis: accum=r[P3] step(r[P2@P5]) */
#define OP_AggStep1 155 /* synopsis: accum=r[P3] step(r[P2@P5]) */
#define OP_AggValue 156 /* synopsis: r[P3]=value N=P2 */
#define OP_AggFinal 157 /* synopsis: accum=r[P1] N=P2 */
#define OP_Expire 158
#define OP_TableLock 159 /* synopsis: iDb=P1 root=P2 write=P3 */
#define OP_VBegin 160
#define OP_VCreate 161
#define OP_VDestroy 162
#define OP_VOpen 163
#define OP_VColumn 164 /* synopsis: r[P3]=vcolumn(P2) */
#define OP_VRename 165
#define OP_Pagecount 166
#define OP_MaxPgcnt 167
#define OP_Trace 168
#define OP_CursorHint 169
#define OP_Noop 170
#define OP_Explain 171
#define OP_Abortable 172
/* Properties such as "out2" or "jump" that are specified in
** comments following the "case" for each opcode in the vdbe.c
** are encoded into bitvectors as follows:
*/
#define OPFLG_JUMP 0x01 /* jump: P2 holds jmp target */
#define OPFLG_IN1 0x02 /* in1: P1 is an input */
#define OPFLG_IN2 0x04 /* in2: P2 is an input */
#define OPFLG_IN3 0x08 /* in3: P3 is an input */
#define OPFLG_OUT2 0x10 /* out2: P2 is an output */
#define OPFLG_OUT3 0x20 /* out3: P3 is an output */
#define OPFLG_INITIALIZER {\
/* 0 */ 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x10,\
/* 8 */ 0x00, 0x01, 0x00, 0x01, 0x01, 0x01, 0x03, 0x03,\
/* 16 */ 0x01, 0x01, 0x03, 0x12, 0x03, 0x01, 0x09, 0x09,\
/* 24 */ 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09,\
/* 32 */ 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,\
/* 40 */ 0x01, 0x23, 0x0b, 0x26, 0x26, 0x01, 0x01, 0x03,\
/* 48 */ 0x03, 0x03, 0x03, 0x03, 0x0b, 0x0b, 0x0b, 0x0b,\
/* 56 */ 0x0b, 0x0b, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00,\
/* 64 */ 0x00, 0x00, 0x02, 0x02, 0x08, 0x00, 0x10, 0x10,\
/* 72 */ 0x10, 0x10, 0x00, 0x10, 0x10, 0x00, 0x00, 0x10,\
/* 80 */ 0x10, 0x00, 0x00, 0x02, 0x02, 0x02, 0x00, 0x00,\
/* 88 */ 0x12, 0x20, 0x00, 0x00, 0x00, 0x10, 0x10, 0x00,\
/* 96 */ 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26,\
/* 104 */ 0x26, 0x26, 0x00, 0x12, 0x00, 0x00, 0x10, 0x00,\
/* 112 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
/* 120 */ 0x10, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
/* 128 */ 0x10, 0x00, 0x00, 0x04, 0x04, 0x00, 0x00, 0x10,\
/* 136 */ 0x10, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00,\
/* 144 */ 0x00, 0x10, 0x00, 0x00, 0x06, 0x10, 0x00, 0x04,\
/* 152 */ 0x1a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
/* 160 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x10,\
/* 168 */ 0x00, 0x00, 0x00, 0x00, 0x00,}
/* The sqlite3P2Values() routine is able to run faster if it knows
** the value of the largest JUMP opcode. The smaller the maximum
** JUMP opcode the better, so the mkopcodeh.tcl script that
** generated this include file strives to group all JUMP opcodes
** together near the beginning of the list.
*/
#define SQLITE_MX_JUMP_OPCODE 61 /* Maximum JUMP opcode */
