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sqlite3session.c
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5804 lines (5306 loc) · 185 KB
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#if defined(SQLITE_ENABLE_SESSION) && defined(SQLITE_ENABLE_PREUPDATE_HOOK)
#include "sqlite3session.h"
#include <assert.h>
#include <string.h>
#ifndef SQLITE_AMALGAMATION
# include "sqliteInt.h"
# include "vdbeInt.h"
#endif
typedef struct SessionTable SessionTable;
typedef struct SessionChange SessionChange;
typedef struct SessionBuffer SessionBuffer;
typedef struct SessionInput SessionInput;
/*
** Minimum chunk size used by streaming versions of functions.
*/
#ifndef SESSIONS_STRM_CHUNK_SIZE
# ifdef SQLITE_TEST
# define SESSIONS_STRM_CHUNK_SIZE 64
# else
# define SESSIONS_STRM_CHUNK_SIZE 1024
# endif
#endif
static int sessions_strm_chunk_size = SESSIONS_STRM_CHUNK_SIZE;
typedef struct SessionHook SessionHook;
struct SessionHook {
void *pCtx;
int (*xOld)(void*,int,sqlite3_value**);
int (*xNew)(void*,int,sqlite3_value**);
int (*xCount)(void*);
int (*xDepth)(void*);
};
/*
** Session handle structure.
*/
struct sqlite3_session {
sqlite3 *db; /* Database handle session is attached to */
char *zDb; /* Name of database session is attached to */
int bEnableSize; /* True if changeset_size() enabled */
int bEnable; /* True if currently recording */
int bIndirect; /* True if all changes are indirect */
int bAutoAttach; /* True to auto-attach tables */
int rc; /* Non-zero if an error has occurred */
void *pFilterCtx; /* First argument to pass to xTableFilter */
int (*xTableFilter)(void *pCtx, const char *zTab);
i64 nMalloc; /* Number of bytes of data allocated */
i64 nMaxChangesetSize;
sqlite3_value *pZeroBlob; /* Value containing X'' */
sqlite3_session *pNext; /* Next session object on same db. */
SessionTable *pTable; /* List of attached tables */
SessionHook hook; /* APIs to grab new and old data with */
};
/*
** Instances of this structure are used to build strings or binary records.
*/
struct SessionBuffer {
u8 *aBuf; /* Pointer to changeset buffer */
int nBuf; /* Size of buffer aBuf */
int nAlloc; /* Size of allocation containing aBuf */
};
/*
** An object of this type is used internally as an abstraction for
** input data. Input data may be supplied either as a single large buffer
** (e.g. sqlite3changeset_start()) or using a stream function (e.g.
** sqlite3changeset_start_strm()).
*/
struct SessionInput {
int bNoDiscard; /* If true, do not discard in InputBuffer() */
int iCurrent; /* Offset in aData[] of current change */
int iNext; /* Offset in aData[] of next change */
u8 *aData; /* Pointer to buffer containing changeset */
int nData; /* Number of bytes in aData */
SessionBuffer buf; /* Current read buffer */
int (*xInput)(void*, void*, int*); /* Input stream call (or NULL) */
void *pIn; /* First argument to xInput */
int bEof; /* Set to true after xInput finished */
};
/*
** Structure for changeset iterators.
*/
struct sqlite3_changeset_iter {
SessionInput in; /* Input buffer or stream */
SessionBuffer tblhdr; /* Buffer to hold apValue/zTab/abPK/ */
int bPatchset; /* True if this is a patchset */
int bInvert; /* True to invert changeset */
int bSkipEmpty; /* Skip noop UPDATE changes */
int rc; /* Iterator error code */
sqlite3_stmt *pConflict; /* Points to conflicting row, if any */
char *zTab; /* Current table */
int nCol; /* Number of columns in zTab */
int op; /* Current operation */
int bIndirect; /* True if current change was indirect */
u8 *abPK; /* Primary key array */
sqlite3_value **apValue; /* old.* and new.* values */
};
/*
** Each session object maintains a set of the following structures, one
** for each table the session object is monitoring. The structures are
** stored in a linked list starting at sqlite3_session.pTable.
**
** The keys of the SessionTable.aChange[] hash table are all rows that have
** been modified in any way since the session object was attached to the
** table.
**
** The data associated with each hash-table entry is a structure containing
** a subset of the initial values that the modified row contained at the
** start of the session. Or no initial values if the row was inserted.
*/
struct SessionTable {
SessionTable *pNext;
char *zName; /* Local name of table */
int nCol; /* Number of columns in table zName */
int bStat1; /* True if this is sqlite_stat1 */
const char **azCol; /* Column names */
u8 *abPK; /* Array of primary key flags */
int nEntry; /* Total number of entries in hash table */
int nChange; /* Size of apChange[] array */
SessionChange **apChange; /* Hash table buckets */
};
/*
** RECORD FORMAT:
**
** The following record format is similar to (but not compatible with) that
** used in SQLite database files. This format is used as part of the
** change-set binary format, and so must be architecture independent.
**
** Unlike the SQLite database record format, each field is self-contained -
** there is no separation of header and data. Each field begins with a
** single byte describing its type, as follows:
**
** 0x00: Undefined value.
** 0x01: Integer value.
** 0x02: Real value.
** 0x03: Text value.
** 0x04: Blob value.
** 0x05: SQL NULL value.
**
** Note that the above match the definitions of SQLITE_INTEGER, SQLITE_TEXT
** and so on in sqlite3.h. For undefined and NULL values, the field consists
** only of the single type byte. For other types of values, the type byte
** is followed by:
**
** Text values:
** A varint containing the number of bytes in the value (encoded using
** UTF-8). Followed by a buffer containing the UTF-8 representation
** of the text value. There is no nul terminator.
**
** Blob values:
** A varint containing the number of bytes in the value, followed by
** a buffer containing the value itself.
**
** Integer values:
** An 8-byte big-endian integer value.
**
** Real values:
** An 8-byte big-endian IEEE 754-2008 real value.
**
** Varint values are encoded in the same way as varints in the SQLite
** record format.
**
** CHANGESET FORMAT:
**
** A changeset is a collection of DELETE, UPDATE and INSERT operations on
** one or more tables. Operations on a single table are grouped together,
** but may occur in any order (i.e. deletes, updates and inserts are all
** mixed together).
**
** Each group of changes begins with a table header:
**
** 1 byte: Constant 0x54 (capital 'T')
** Varint: Number of columns in the table.
** nCol bytes: 0x01 for PK columns, 0x00 otherwise.
** N bytes: Unqualified table name (encoded using UTF-8). Nul-terminated.
**
** Followed by one or more changes to the table.
**
** 1 byte: Either SQLITE_INSERT (0x12), UPDATE (0x17) or DELETE (0x09).
** 1 byte: The "indirect-change" flag.
** old.* record: (delete and update only)
** new.* record: (insert and update only)
**
** The "old.*" and "new.*" records, if present, are N field records in the
** format described above under "RECORD FORMAT", where N is the number of
** columns in the table. The i'th field of each record is associated with
** the i'th column of the table, counting from left to right in the order
** in which columns were declared in the CREATE TABLE statement.
**
** The new.* record that is part of each INSERT change contains the values
** that make up the new row. Similarly, the old.* record that is part of each
** DELETE change contains the values that made up the row that was deleted
** from the database. In the changeset format, the records that are part
** of INSERT or DELETE changes never contain any undefined (type byte 0x00)
** fields.
**
** Within the old.* record associated with an UPDATE change, all fields
** associated with table columns that are not PRIMARY KEY columns and are
** not modified by the UPDATE change are set to "undefined". Other fields
** are set to the values that made up the row before the UPDATE that the
** change records took place. Within the new.* record, fields associated
** with table columns modified by the UPDATE change contain the new
** values. Fields associated with table columns that are not modified
** are set to "undefined".
**
** PATCHSET FORMAT:
**
** A patchset is also a collection of changes. It is similar to a changeset,
** but leaves undefined those fields that are not useful if no conflict
** resolution is required when applying the changeset.
**
** Each group of changes begins with a table header:
**
** 1 byte: Constant 0x50 (capital 'P')
** Varint: Number of columns in the table.
** nCol bytes: 0x01 for PK columns, 0x00 otherwise.
** N bytes: Unqualified table name (encoded using UTF-8). Nul-terminated.
**
** Followed by one or more changes to the table.
**
** 1 byte: Either SQLITE_INSERT (0x12), UPDATE (0x17) or DELETE (0x09).
** 1 byte: The "indirect-change" flag.
** single record: (PK fields for DELETE, PK and modified fields for UPDATE,
** full record for INSERT).
**
** As in the changeset format, each field of the single record that is part
** of a patchset change is associated with the correspondingly positioned
** table column, counting from left to right within the CREATE TABLE
** statement.
**
** For a DELETE change, all fields within the record except those associated
** with PRIMARY KEY columns are omitted. The PRIMARY KEY fields contain the
** values identifying the row to delete.
**
** For an UPDATE change, all fields except those associated with PRIMARY KEY
** columns and columns that are modified by the UPDATE are set to "undefined".
** PRIMARY KEY fields contain the values identifying the table row to update,
** and fields associated with modified columns contain the new column values.
**
** The records associated with INSERT changes are in the same format as for
** changesets. It is not possible for a record associated with an INSERT
** change to contain a field set to "undefined".
**
** REBASE BLOB FORMAT:
**
** A rebase blob may be output by sqlite3changeset_apply_v2() and its
** streaming equivalent for use with the sqlite3_rebaser APIs to rebase
** existing changesets. A rebase blob contains one entry for each conflict
** resolved using either the OMIT or REPLACE strategies within the apply_v2()
** call.
**
** The format used for a rebase blob is very similar to that used for
** changesets. All entries related to a single table are grouped together.
**
** Each group of entries begins with a table header in changeset format:
**
** 1 byte: Constant 0x54 (capital 'T')
** Varint: Number of columns in the table.
** nCol bytes: 0x01 for PK columns, 0x00 otherwise.
** N bytes: Unqualified table name (encoded using UTF-8). Nul-terminated.
**
** Followed by one or more entries associated with the table.
**
** 1 byte: Either SQLITE_INSERT (0x12), DELETE (0x09).
** 1 byte: Flag. 0x01 for REPLACE, 0x00 for OMIT.
** record: (in the record format defined above).
**
** In a rebase blob, the first field is set to SQLITE_INSERT if the change
** that caused the conflict was an INSERT or UPDATE, or to SQLITE_DELETE if
** it was a DELETE. The second field is set to 0x01 if the conflict
** resolution strategy was REPLACE, or 0x00 if it was OMIT.
**
** If the change that caused the conflict was a DELETE, then the single
** record is a copy of the old.* record from the original changeset. If it
** was an INSERT, then the single record is a copy of the new.* record. If
** the conflicting change was an UPDATE, then the single record is a copy
** of the new.* record with the PK fields filled in based on the original
** old.* record.
*/
/*
** For each row modified during a session, there exists a single instance of
** this structure stored in a SessionTable.aChange[] hash table.
*/
struct SessionChange {
u8 op; /* One of UPDATE, DELETE, INSERT */
u8 bIndirect; /* True if this change is "indirect" */
int nMaxSize; /* Max size of eventual changeset record */
int nRecord; /* Number of bytes in buffer aRecord[] */
u8 *aRecord; /* Buffer containing old.* record */
SessionChange *pNext; /* For hash-table collisions */
};
/*
** Write a varint with value iVal into the buffer at aBuf. Return the
** number of bytes written.
*/
static int sessionVarintPut(u8 *aBuf, int iVal){
return putVarint32(aBuf, iVal);
}
/*
** Return the number of bytes required to store value iVal as a varint.
*/
static int sessionVarintLen(int iVal){
return sqlite3VarintLen(iVal);
}
/*
** Read a varint value from aBuf[] into *piVal. Return the number of
** bytes read.
*/
static int sessionVarintGet(u8 *aBuf, int *piVal){
return getVarint32(aBuf, *piVal);
}
/* Load an unaligned and unsigned 32-bit integer */
#define SESSION_UINT32(x) (((u32)(x)[0]<<24)|((x)[1]<<16)|((x)[2]<<8)|(x)[3])
/*
** Read a 64-bit big-endian integer value from buffer aRec[]. Return
** the value read.
*/
static sqlite3_int64 sessionGetI64(u8 *aRec){
u64 x = SESSION_UINT32(aRec);
u32 y = SESSION_UINT32(aRec+4);
x = (x<<32) + y;
return (sqlite3_int64)x;
}
/*
** Write a 64-bit big-endian integer value to the buffer aBuf[].
*/
static void sessionPutI64(u8 *aBuf, sqlite3_int64 i){
aBuf[0] = (i>>56) & 0xFF;
aBuf[1] = (i>>48) & 0xFF;
aBuf[2] = (i>>40) & 0xFF;
aBuf[3] = (i>>32) & 0xFF;
aBuf[4] = (i>>24) & 0xFF;
aBuf[5] = (i>>16) & 0xFF;
aBuf[6] = (i>> 8) & 0xFF;
aBuf[7] = (i>> 0) & 0xFF;
}
/*
** This function is used to serialize the contents of value pValue (see
** comment titled "RECORD FORMAT" above).
**
** If it is non-NULL, the serialized form of the value is written to
** buffer aBuf. *pnWrite is set to the number of bytes written before
** returning. Or, if aBuf is NULL, the only thing this function does is
** set *pnWrite.
**
** If no error occurs, SQLITE_OK is returned. Or, if an OOM error occurs
** within a call to sqlite3_value_text() (may fail if the db is utf-16))
** SQLITE_NOMEM is returned.
*/
static int sessionSerializeValue(
u8 *aBuf, /* If non-NULL, write serialized value here */
sqlite3_value *pValue, /* Value to serialize */
sqlite3_int64 *pnWrite /* IN/OUT: Increment by bytes written */
){
int nByte; /* Size of serialized value in bytes */
if( pValue ){
int eType; /* Value type (SQLITE_NULL, TEXT etc.) */
eType = sqlite3_value_type(pValue);
if( aBuf ) aBuf[0] = eType;
switch( eType ){
case SQLITE_NULL:
nByte = 1;
break;
case SQLITE_INTEGER:
case SQLITE_FLOAT:
if( aBuf ){
/* TODO: SQLite does something special to deal with mixed-endian
** floating point values (e.g. ARM7). This code probably should
** too. */
u64 i;
if( eType==SQLITE_INTEGER ){
i = (u64)sqlite3_value_int64(pValue);
}else{
double r;
assert( sizeof(double)==8 && sizeof(u64)==8 );
r = sqlite3_value_double(pValue);
memcpy(&i, &r, 8);
}
sessionPutI64(&aBuf[1], i);
}
nByte = 9;
break;
default: {
u8 *z;
int n;
int nVarint;
assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
if( eType==SQLITE_TEXT ){
z = (u8 *)sqlite3_value_text(pValue);
}else{
z = (u8 *)sqlite3_value_blob(pValue);
}
n = sqlite3_value_bytes(pValue);
if( z==0 && (eType!=SQLITE_BLOB || n>0) ) return SQLITE_NOMEM;
nVarint = sessionVarintLen(n);
if( aBuf ){
sessionVarintPut(&aBuf[1], n);
if( n>0 ) memcpy(&aBuf[nVarint + 1], z, n);
}
nByte = 1 + nVarint + n;
break;
}
}
}else{
nByte = 1;
if( aBuf ) aBuf[0] = '\0';
}
if( pnWrite ) *pnWrite += nByte;
return SQLITE_OK;
}
/*
** Allocate and return a pointer to a buffer nByte bytes in size. If
** pSession is not NULL, increase the sqlite3_session.nMalloc variable
** by the number of bytes allocated.
*/
static void *sessionMalloc64(sqlite3_session *pSession, i64 nByte){
void *pRet = sqlite3_malloc64(nByte);
if( pSession ) pSession->nMalloc += sqlite3_msize(pRet);
return pRet;
}
/*
** Free buffer pFree, which must have been allocated by an earlier
** call to sessionMalloc64(). If pSession is not NULL, decrease the
** sqlite3_session.nMalloc counter by the number of bytes freed.
*/
static void sessionFree(sqlite3_session *pSession, void *pFree){
if( pSession ) pSession->nMalloc -= sqlite3_msize(pFree);
sqlite3_free(pFree);
}
/*
** This macro is used to calculate hash key values for data structures. In
** order to use this macro, the entire data structure must be represented
** as a series of unsigned integers. In order to calculate a hash-key value
** for a data structure represented as three such integers, the macro may
** then be used as follows:
**
** int hash_key_value;
** hash_key_value = HASH_APPEND(0, <value 1>);
** hash_key_value = HASH_APPEND(hash_key_value, <value 2>);
** hash_key_value = HASH_APPEND(hash_key_value, <value 3>);
**
** In practice, the data structures this macro is used for are the primary
** key values of modified rows.
*/
#define HASH_APPEND(hash, add) ((hash) << 3) ^ (hash) ^ (unsigned int)(add)
/*
** Append the hash of the 64-bit integer passed as the second argument to the
** hash-key value passed as the first. Return the new hash-key value.
*/
static unsigned int sessionHashAppendI64(unsigned int h, i64 i){
h = HASH_APPEND(h, i & 0xFFFFFFFF);
return HASH_APPEND(h, (i>>32)&0xFFFFFFFF);
}
/*
** Append the hash of the blob passed via the second and third arguments to
** the hash-key value passed as the first. Return the new hash-key value.
*/
static unsigned int sessionHashAppendBlob(unsigned int h, int n, const u8 *z){
int i;
for(i=0; i<n; i++) h = HASH_APPEND(h, z[i]);
return h;
}
/*
** Append the hash of the data type passed as the second argument to the
** hash-key value passed as the first. Return the new hash-key value.
*/
static unsigned int sessionHashAppendType(unsigned int h, int eType){
return HASH_APPEND(h, eType);
}
/*
** This function may only be called from within a pre-update callback.
** It calculates a hash based on the primary key values of the old.* or
** new.* row currently available and, assuming no error occurs, writes it to
** *piHash before returning. If the primary key contains one or more NULL
** values, *pbNullPK is set to true before returning.
**
** If an error occurs, an SQLite error code is returned and the final values
** of *piHash asn *pbNullPK are undefined. Otherwise, SQLITE_OK is returned
** and the output variables are set as described above.
*/
static int sessionPreupdateHash(
sqlite3_session *pSession, /* Session object that owns pTab */
SessionTable *pTab, /* Session table handle */
int bNew, /* True to hash the new.* PK */
int *piHash, /* OUT: Hash value */
int *pbNullPK /* OUT: True if there are NULL values in PK */
){
unsigned int h = 0; /* Hash value to return */
int i; /* Used to iterate through columns */
assert( *pbNullPK==0 );
assert( pTab->nCol==pSession->hook.xCount(pSession->hook.pCtx) );
for(i=0; i<pTab->nCol; i++){
if( pTab->abPK[i] ){
int rc;
int eType;
sqlite3_value *pVal;
if( bNew ){
rc = pSession->hook.xNew(pSession->hook.pCtx, i, &pVal);
}else{
rc = pSession->hook.xOld(pSession->hook.pCtx, i, &pVal);
}
if( rc!=SQLITE_OK ) return rc;
eType = sqlite3_value_type(pVal);
h = sessionHashAppendType(h, eType);
if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
i64 iVal;
if( eType==SQLITE_INTEGER ){
iVal = sqlite3_value_int64(pVal);
}else{
double rVal = sqlite3_value_double(pVal);
assert( sizeof(iVal)==8 && sizeof(rVal)==8 );
memcpy(&iVal, &rVal, 8);
}
h = sessionHashAppendI64(h, iVal);
}else if( eType==SQLITE_TEXT || eType==SQLITE_BLOB ){
const u8 *z;
int n;
if( eType==SQLITE_TEXT ){
z = (const u8 *)sqlite3_value_text(pVal);
}else{
z = (const u8 *)sqlite3_value_blob(pVal);
}
n = sqlite3_value_bytes(pVal);
if( !z && (eType!=SQLITE_BLOB || n>0) ) return SQLITE_NOMEM;
h = sessionHashAppendBlob(h, n, z);
}else{
assert( eType==SQLITE_NULL );
assert( pTab->bStat1==0 || i!=1 );
*pbNullPK = 1;
}
}
}
*piHash = (h % pTab->nChange);
return SQLITE_OK;
}
/*
** The buffer that the argument points to contains a serialized SQL value.
** Return the number of bytes of space occupied by the value (including
** the type byte).
*/
static int sessionSerialLen(u8 *a){
int e = *a;
int n;
if( e==0 || e==0xFF ) return 1;
if( e==SQLITE_NULL ) return 1;
if( e==SQLITE_INTEGER || e==SQLITE_FLOAT ) return 9;
return sessionVarintGet(&a[1], &n) + 1 + n;
}
/*
** Based on the primary key values stored in change aRecord, calculate a
** hash key. Assume the has table has nBucket buckets. The hash keys
** calculated by this function are compatible with those calculated by
** sessionPreupdateHash().
**
** The bPkOnly argument is non-zero if the record at aRecord[] is from
** a patchset DELETE. In this case the non-PK fields are omitted entirely.
*/
static unsigned int sessionChangeHash(
SessionTable *pTab, /* Table handle */
int bPkOnly, /* Record consists of PK fields only */
u8 *aRecord, /* Change record */
int nBucket /* Assume this many buckets in hash table */
){
unsigned int h = 0; /* Value to return */
int i; /* Used to iterate through columns */
u8 *a = aRecord; /* Used to iterate through change record */
for(i=0; i<pTab->nCol; i++){
int eType = *a;
int isPK = pTab->abPK[i];
if( bPkOnly && isPK==0 ) continue;
/* It is not possible for eType to be SQLITE_NULL here. The session
** module does not record changes for rows with NULL values stored in
** primary key columns. */
assert( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT
|| eType==SQLITE_TEXT || eType==SQLITE_BLOB
|| eType==SQLITE_NULL || eType==0
);
assert( !isPK || (eType!=0 && eType!=SQLITE_NULL) );
if( isPK ){
a++;
h = sessionHashAppendType(h, eType);
if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
h = sessionHashAppendI64(h, sessionGetI64(a));
a += 8;
}else{
int n;
a += sessionVarintGet(a, &n);
h = sessionHashAppendBlob(h, n, a);
a += n;
}
}else{
a += sessionSerialLen(a);
}
}
return (h % nBucket);
}
/*
** Arguments aLeft and aRight are pointers to change records for table pTab.
** This function returns true if the two records apply to the same row (i.e.
** have the same values stored in the primary key columns), or false
** otherwise.
*/
static int sessionChangeEqual(
SessionTable *pTab, /* Table used for PK definition */
int bLeftPkOnly, /* True if aLeft[] contains PK fields only */
u8 *aLeft, /* Change record */
int bRightPkOnly, /* True if aRight[] contains PK fields only */
u8 *aRight /* Change record */
){
u8 *a1 = aLeft; /* Cursor to iterate through aLeft */
u8 *a2 = aRight; /* Cursor to iterate through aRight */
int iCol; /* Used to iterate through table columns */
for(iCol=0; iCol<pTab->nCol; iCol++){
if( pTab->abPK[iCol] ){
int n1 = sessionSerialLen(a1);
int n2 = sessionSerialLen(a2);
if( n1!=n2 || memcmp(a1, a2, n1) ){
return 0;
}
a1 += n1;
a2 += n2;
}else{
if( bLeftPkOnly==0 ) a1 += sessionSerialLen(a1);
if( bRightPkOnly==0 ) a2 += sessionSerialLen(a2);
}
}
return 1;
}
/*
** Arguments aLeft and aRight both point to buffers containing change
** records with nCol columns. This function "merges" the two records into
** a single records which is written to the buffer at *paOut. *paOut is
** then set to point to one byte after the last byte written before
** returning.
**
** The merging of records is done as follows: For each column, if the
** aRight record contains a value for the column, copy the value from
** their. Otherwise, if aLeft contains a value, copy it. If neither
** record contains a value for a given column, then neither does the
** output record.
*/
static void sessionMergeRecord(
u8 **paOut,
int nCol,
u8 *aLeft,
u8 *aRight
){
u8 *a1 = aLeft; /* Cursor used to iterate through aLeft */
u8 *a2 = aRight; /* Cursor used to iterate through aRight */
u8 *aOut = *paOut; /* Output cursor */
int iCol; /* Used to iterate from 0 to nCol */
for(iCol=0; iCol<nCol; iCol++){
int n1 = sessionSerialLen(a1);
int n2 = sessionSerialLen(a2);
if( *a2 ){
memcpy(aOut, a2, n2);
aOut += n2;
}else{
memcpy(aOut, a1, n1);
aOut += n1;
}
a1 += n1;
a2 += n2;
}
*paOut = aOut;
}
/*
** This is a helper function used by sessionMergeUpdate().
**
** When this function is called, both *paOne and *paTwo point to a value
** within a change record. Before it returns, both have been advanced so
** as to point to the next value in the record.
**
** If, when this function is called, *paTwo points to a valid value (i.e.
** *paTwo[0] is not 0x00 - the "no value" placeholder), a copy of the *paTwo
** pointer is returned and *pnVal is set to the number of bytes in the
** serialized value. Otherwise, a copy of *paOne is returned and *pnVal
** set to the number of bytes in the value at *paOne. If *paOne points
** to the "no value" placeholder, *pnVal is set to 1. In other words:
**
** if( *paTwo is valid ) return *paTwo;
** return *paOne;
**
*/
static u8 *sessionMergeValue(
u8 **paOne, /* IN/OUT: Left-hand buffer pointer */
u8 **paTwo, /* IN/OUT: Right-hand buffer pointer */
int *pnVal /* OUT: Bytes in returned value */
){
u8 *a1 = *paOne;
u8 *a2 = *paTwo;
u8 *pRet = 0;
int n1;
assert( a1 );
if( a2 ){
int n2 = sessionSerialLen(a2);
if( *a2 ){
*pnVal = n2;
pRet = a2;
}
*paTwo = &a2[n2];
}
n1 = sessionSerialLen(a1);
if( pRet==0 ){
*pnVal = n1;
pRet = a1;
}
*paOne = &a1[n1];
return pRet;
}
/*
** This function is used by changeset_concat() to merge two UPDATE changes
** on the same row.
*/
static int sessionMergeUpdate(
u8 **paOut, /* IN/OUT: Pointer to output buffer */
SessionTable *pTab, /* Table change pertains to */
int bPatchset, /* True if records are patchset records */
u8 *aOldRecord1, /* old.* record for first change */
u8 *aOldRecord2, /* old.* record for second change */
u8 *aNewRecord1, /* new.* record for first change */
u8 *aNewRecord2 /* new.* record for second change */
){
u8 *aOld1 = aOldRecord1;
u8 *aOld2 = aOldRecord2;
u8 *aNew1 = aNewRecord1;
u8 *aNew2 = aNewRecord2;
u8 *aOut = *paOut;
int i;
if( bPatchset==0 ){
int bRequired = 0;
assert( aOldRecord1 && aNewRecord1 );
/* Write the old.* vector first. */
for(i=0; i<pTab->nCol; i++){
int nOld;
u8 *aOld;
int nNew;
u8 *aNew;
aOld = sessionMergeValue(&aOld1, &aOld2, &nOld);
aNew = sessionMergeValue(&aNew1, &aNew2, &nNew);
if( pTab->abPK[i] || nOld!=nNew || memcmp(aOld, aNew, nNew) ){
if( pTab->abPK[i]==0 ) bRequired = 1;
memcpy(aOut, aOld, nOld);
aOut += nOld;
}else{
*(aOut++) = '\0';
}
}
if( !bRequired ) return 0;
}
/* Write the new.* vector */
aOld1 = aOldRecord1;
aOld2 = aOldRecord2;
aNew1 = aNewRecord1;
aNew2 = aNewRecord2;
for(i=0; i<pTab->nCol; i++){
int nOld;
u8 *aOld;
int nNew;
u8 *aNew;
aOld = sessionMergeValue(&aOld1, &aOld2, &nOld);
aNew = sessionMergeValue(&aNew1, &aNew2, &nNew);
if( bPatchset==0
&& (pTab->abPK[i] || (nOld==nNew && 0==memcmp(aOld, aNew, nNew)))
){
*(aOut++) = '\0';
}else{
memcpy(aOut, aNew, nNew);
aOut += nNew;
}
}
*paOut = aOut;
return 1;
}
/*
** This function is only called from within a pre-update-hook callback.
** It determines if the current pre-update-hook change affects the same row
** as the change stored in argument pChange. If so, it returns true. Otherwise
** if the pre-update-hook does not affect the same row as pChange, it returns
** false.
*/
static int sessionPreupdateEqual(
sqlite3_session *pSession, /* Session object that owns SessionTable */
SessionTable *pTab, /* Table associated with change */
SessionChange *pChange, /* Change to compare to */
int op /* Current pre-update operation */
){
int iCol; /* Used to iterate through columns */
u8 *a = pChange->aRecord; /* Cursor used to scan change record */
assert( op==SQLITE_INSERT || op==SQLITE_UPDATE || op==SQLITE_DELETE );
for(iCol=0; iCol<pTab->nCol; iCol++){
if( !pTab->abPK[iCol] ){
a += sessionSerialLen(a);
}else{
sqlite3_value *pVal; /* Value returned by preupdate_new/old */
int rc; /* Error code from preupdate_new/old */
int eType = *a++; /* Type of value from change record */
/* The following calls to preupdate_new() and preupdate_old() can not
** fail. This is because they cache their return values, and by the
** time control flows to here they have already been called once from
** within sessionPreupdateHash(). The first two asserts below verify
** this (that the method has already been called). */
if( op==SQLITE_INSERT ){
/* assert( db->pPreUpdate->pNewUnpacked || db->pPreUpdate->aNew ); */
rc = pSession->hook.xNew(pSession->hook.pCtx, iCol, &pVal);
}else{
/* assert( db->pPreUpdate->pUnpacked ); */
rc = pSession->hook.xOld(pSession->hook.pCtx, iCol, &pVal);
}
assert( rc==SQLITE_OK );
if( sqlite3_value_type(pVal)!=eType ) return 0;
/* A SessionChange object never has a NULL value in a PK column */
assert( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT
|| eType==SQLITE_BLOB || eType==SQLITE_TEXT
);
if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
i64 iVal = sessionGetI64(a);
a += 8;
if( eType==SQLITE_INTEGER ){
if( sqlite3_value_int64(pVal)!=iVal ) return 0;
}else{
double rVal;
assert( sizeof(iVal)==8 && sizeof(rVal)==8 );
memcpy(&rVal, &iVal, 8);
if( sqlite3_value_double(pVal)!=rVal ) return 0;
}
}else{
int n;
const u8 *z;
a += sessionVarintGet(a, &n);
if( sqlite3_value_bytes(pVal)!=n ) return 0;
if( eType==SQLITE_TEXT ){
z = sqlite3_value_text(pVal);
}else{
z = sqlite3_value_blob(pVal);
}
if( n>0 && memcmp(a, z, n) ) return 0;
a += n;
}
}
}
return 1;
}
/*
** If required, grow the hash table used to store changes on table pTab
** (part of the session pSession). If a fatal OOM error occurs, set the
** session object to failed and return SQLITE_ERROR. Otherwise, return
** SQLITE_OK.
**
** It is possible that a non-fatal OOM error occurs in this function. In
** that case the hash-table does not grow, but SQLITE_OK is returned anyway.
** Growing the hash table in this case is a performance optimization only,
** it is not required for correct operation.
*/
static int sessionGrowHash(
sqlite3_session *pSession, /* For memory accounting. May be NULL */
int bPatchset,
SessionTable *pTab
){
if( pTab->nChange==0 || pTab->nEntry>=(pTab->nChange/2) ){
int i;
SessionChange **apNew;
sqlite3_int64 nNew = 2*(sqlite3_int64)(pTab->nChange ? pTab->nChange : 128);
apNew = (SessionChange**)sessionMalloc64(
pSession, sizeof(SessionChange*) * nNew
);
if( apNew==0 ){
if( pTab->nChange==0 ){
return SQLITE_ERROR;
}
return SQLITE_OK;
}
memset(apNew, 0, sizeof(SessionChange *) * nNew);
for(i=0; i<pTab->nChange; i++){
SessionChange *p;
SessionChange *pNext;
for(p=pTab->apChange[i]; p; p=pNext){
int bPkOnly = (p->op==SQLITE_DELETE && bPatchset);
int iHash = sessionChangeHash(pTab, bPkOnly, p->aRecord, nNew);
pNext = p->pNext;
p->pNext = apNew[iHash];
apNew[iHash] = p;
}
}
sessionFree(pSession, pTab->apChange);
pTab->nChange = nNew;
pTab->apChange = apNew;
}
return SQLITE_OK;
}
/*
** This function queries the database for the names of the columns of table
** zThis, in schema zDb.
**
** Otherwise, if they are not NULL, variable *pnCol is set to the number
** of columns in the database table and variable *pzTab is set to point to a
** nul-terminated copy of the table name. *pazCol (if not NULL) is set to
** point to an array of pointers to column names. And *pabPK (again, if not
** NULL) is set to point to an array of booleans - true if the corresponding
** column is part of the primary key.
**
** For example, if the table is declared as:
**
** CREATE TABLE tbl1(w, x, y, z, PRIMARY KEY(w, z));
**
** Then the four output variables are populated as follows:
**
** *pnCol = 4
** *pzTab = "tbl1"
** *pazCol = {"w", "x", "y", "z"}
** *pabPK = {1, 0, 0, 1}
**
** All returned buffers are part of the same single allocation, which must
** be freed using sqlite3_free() by the caller
*/
static int sessionTableInfo(
sqlite3_session *pSession, /* For memory accounting. May be NULL */
sqlite3 *db, /* Database connection */
const char *zDb, /* Name of attached database (e.g. "main") */
const char *zThis, /* Table name */
int *pnCol, /* OUT: number of columns */
const char **pzTab, /* OUT: Copy of zThis */
const char ***pazCol, /* OUT: Array of column names for table */
u8 **pabPK /* OUT: Array of booleans - true for PK col */