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Overview
Comment: | Small simplification to the prepare statement opcode memory reuse logic. Easier to read, and slightly smaller and faster. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
8a1deae497edf3fa43fa96152d140405 |
User & Date: | drh 2016-01-25 02:15:02.255 |
Context
2016-01-25
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13:55 | Add the SQLITE_EXTRA_DURABLE compile-time option. (check-in: 30671345b1 user: drh tags: trunk) | |
02:15 | Small simplification to the prepare statement opcode memory reuse logic. Easier to read, and slightly smaller and faster. (check-in: 8a1deae497 user: drh tags: trunk) | |
01:07 | Small simplification and performance improvement in memsys5Free(). (check-in: 0a9cff5c48 user: drh tags: trunk) | |
Changes
Changes to src/vdbeaux.c.
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1717 1718 1719 1720 1721 1722 1723 | } z[j] = 0; sqlite3IoTrace("SQL %s\n", z); } } #endif /* !SQLITE_OMIT_TRACE && SQLITE_ENABLE_IOTRACE */ | > > > | > > > > > | > > | > > < | | < < | < < | < > | < < < < < | | < > | | | | | | 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 | } z[j] = 0; sqlite3IoTrace("SQL %s\n", z); } } #endif /* !SQLITE_OMIT_TRACE && SQLITE_ENABLE_IOTRACE */ /* An instance of this object describes bulk memory available for use ** by subcomponents of a prepared statement. Space is allocated out ** of a ReusableSpace object by the allocSpace() routine below. */ struct ReusableSpace { u8 *pSpace; /* Available memory */ int nFree; /* Bytes of available memory */ int nNeeded; /* Total bytes that could not be allocated */ }; /* Try to allocate nByte bytes of 8-byte aligned bulk memory for pBuf ** from the ReusableSpace object. Return a pointer to the allocated ** memory on success. If insufficient memory is available in the ** ReusableSpace object, increase the ReusableSpace.nNeeded ** value by the amount needed and return NULL. ** ** If pBuf is not initially NULL, that means that the memory has already ** been allocated by a prior call to this routine, so just return a copy ** of pBuf and leave ReusableSpace unchanged. ** ** This allocator is employed to repurpose unused slots at the end of the ** opcode array of prepared state for other memory needs of the prepared ** statement. */ static void *allocSpace( struct ReusableSpace *p, /* Bulk memory available for allocation */ void *pBuf, /* Pointer to a prior allocation */ int nByte /* Bytes of memory needed */ ){ assert( EIGHT_BYTE_ALIGNMENT(p->pSpace) ); if( pBuf==0 ){ nByte = ROUND8(nByte); if( nByte <= p->nFree ){ p->nFree -= nByte; pBuf = &p->pSpace[p->nFree]; }else{ p->nNeeded += nByte; } } assert( EIGHT_BYTE_ALIGNMENT(pBuf) ); return pBuf; } /* |
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1827 1828 1829 1830 1831 1832 1833 | sqlite3 *db; /* The database connection */ int nVar; /* Number of parameters */ int nMem; /* Number of VM memory registers */ int nCursor; /* Number of cursors required */ int nArg; /* Number of arguments in subprograms */ int nOnce; /* Number of OP_Once instructions */ int n; /* Loop counter */ | | < < | | | < < | | | | | | | | | | | | | | | | | | < | | | | < < | | | 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 | sqlite3 *db; /* The database connection */ int nVar; /* Number of parameters */ int nMem; /* Number of VM memory registers */ int nCursor; /* Number of cursors required */ int nArg; /* Number of arguments in subprograms */ int nOnce; /* Number of OP_Once instructions */ int n; /* Loop counter */ struct ReusableSpace x; /* Reusable bulk memory */ assert( p!=0 ); assert( p->nOp>0 ); assert( pParse!=0 ); assert( p->magic==VDBE_MAGIC_INIT ); assert( pParse==p->pParse ); db = p->db; assert( db->mallocFailed==0 ); nVar = pParse->nVar; nMem = pParse->nMem; nCursor = pParse->nTab; nArg = pParse->nMaxArg; nOnce = pParse->nOnce; if( nOnce==0 ) nOnce = 1; /* Ensure at least one byte in p->aOnceFlag[] */ /* For each cursor required, also allocate a memory cell. Memory ** cells (nMem+1-nCursor)..nMem, inclusive, will never be used by ** the vdbe program. Instead they are used to allocate memory for ** VdbeCursor/BtCursor structures. The blob of memory associated with ** cursor 0 is stored in memory cell nMem. Memory cell (nMem-1) ** stores the blob of memory associated with cursor 1, etc. ** ** See also: allocateCursor(). */ nMem += nCursor; /* Figure out how much reusable memory is available at the end of the ** opcode array. This extra memory will be reallocated for other elements ** of the prepared statement. */ n = ROUND8(sizeof(Op)*p->nOp); /* Bytes of opcode memory used */ x.pSpace = &((u8*)p->aOp)[n]; /* Unused opcode memory */ assert( EIGHT_BYTE_ALIGNMENT(x.pSpace) ); x.nFree = ROUNDDOWN8(pParse->szOpAlloc - n); /* Bytes of unused memory */ assert( x.nFree>=0 ); if( x.nFree>0 ){ memset(x.pSpace, 0, x.nFree); assert( EIGHT_BYTE_ALIGNMENT(&x.pSpace[x.nFree]) ); } resolveP2Values(p, &nArg); p->usesStmtJournal = (u8)(pParse->isMultiWrite && pParse->mayAbort); if( pParse->explain && nMem<10 ){ nMem = 10; } p->expired = 0; /* Memory for registers, parameters, cursor, etc, is allocated in one or two ** passes. On the first pass, we try to reuse unused memory at the ** end of the opcode array. If we are unable to satisfy all memory ** requirements by reusing the opcode array tail, then the second ** pass will fill in the remainder using a fresh memory allocation. ** ** This two-pass approach that reuses as much memory as possible from ** the leftover memory at the end of the opcode array. This can significantly ** reduce the amount of memory held by a prepared statement. */ do { x.nNeeded = 0; p->aMem = allocSpace(&x, p->aMem, nMem*sizeof(Mem)); p->aVar = allocSpace(&x, p->aVar, nVar*sizeof(Mem)); p->apArg = allocSpace(&x, p->apArg, nArg*sizeof(Mem*)); p->apCsr = allocSpace(&x, p->apCsr, nCursor*sizeof(VdbeCursor*)); p->aOnceFlag = allocSpace(&x, p->aOnceFlag, nOnce); #ifdef SQLITE_ENABLE_STMT_SCANSTATUS p->anExec = allocSpace(&x, p->anExec, p->nOp*sizeof(i64)); #endif if( x.nNeeded==0 ) break; x.pSpace = p->pFree = sqlite3DbMallocZero(db, x.nNeeded); x.nFree = x.nNeeded; }while( !db->mallocFailed ); p->nCursor = nCursor; p->nOnceFlag = nOnce; if( p->aVar ){ p->nVar = (ynVar)nVar; for(n=0; n<nVar; n++){ p->aVar[n].flags = MEM_Null; |
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