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Change the code that collects samples for sqlite_stat2 so that the first sample taken is the (nRow/(2*SQLITE_INDEX_SAMPLES))th entry in the index, where nRow is the total number of index entries.

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FossilOrigin-Name: cbfe6e9df39684607cbc9637e3fb3c5ee6af2515
This commit is contained in:
dan
2009-08-20 09:11:06 +00:00
parent cdaca55eb1
commit 68c4dbbdfc
4 changed files with 49 additions and 53 deletions
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38
src/analyze.c
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@@ -124,11 +124,13 @@ static void analyzeOneTable(
int regRec = iMem++; /* Register holding completed record */
int regTemp = iMem++; /* Temporary use register */
int regRowid = iMem++; /* Rowid for the inserted record */
#ifdef SQLITE_ENABLE_STAT2
int regTemp2 = iMem++; /* Temporary use register */
int regSamplerecno = iMem++; /* Next sample index record number */
int regRecno = iMem++; /* Register next index record number */
int regCount = iMem++; /* Total number of records in table */
int regSamplerecno = iMem++; /* Index of next sample to record */
int regRecno = iMem++; /* Current sample index */
int regLast = iMem++; /* Index of last sample to record */
int regFirst = iMem++; /* Index of first sample to record */
#endif
v = sqlite3GetVdbe(pParse);
@@ -171,26 +173,29 @@ static void analyzeOneTable(
sqlite3VdbeAddOp4(v, OP_String8, 0, regIdxname, 0, pIdx->zName, 0);
#ifdef SQLITE_ENABLE_STAT2
/* If this iteration of the loop is generating code to analyze the
** first index in the pTab->pIndex list, then register regCount has
** first index in the pTab->pIndex list, then register regLast has
** not been populated. In this case populate it now. */
if( pTab->pIndex==pIdx ){
sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regCount);
sqlite3VdbeAddOp2(v, OP_Integer, SQLITE_INDEX_SAMPLES, regSamplerecno);
sqlite3VdbeAddOp2(v, OP_Integer, SQLITE_INDEX_SAMPLES*2-1, regTemp);
sqlite3VdbeAddOp2(v, OP_Integer, SQLITE_INDEX_SAMPLES*2, regTemp2);
sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regLast);
sqlite3VdbeAddOp2(v, OP_Null, 0, regFirst);
addr = sqlite3VdbeAddOp3(v, OP_Lt, regSamplerecno, 0, regLast);
sqlite3VdbeAddOp3(v, OP_Divide, regTemp2, regLast, regFirst);
sqlite3VdbeAddOp3(v, OP_Multiply, regLast, regTemp, regLast);
sqlite3VdbeAddOp2(v, OP_AddImm, regLast, SQLITE_INDEX_SAMPLES*2-2);
sqlite3VdbeAddOp3(v, OP_Divide, regTemp2, regLast, regLast);
sqlite3VdbeJumpHere(v, addr);
}
/* Zero the regSampleno and regRecno registers. */
sqlite3VdbeAddOp2(v, OP_Integer, 0, regSampleno);
sqlite3VdbeAddOp2(v, OP_Integer, 0, regRecno);
/* If there are less than INDEX_SAMPLES records in the index, then
** set the contents of regSampleRecno to integer value INDEX_SAMPLES.
** Otherwise, set it to zero. This is to ensure that if there are
** less than the said number of entries in the index, no samples at
** all are collected. */
sqlite3VdbeAddOp2(v, OP_Integer, SQLITE_INDEX_SAMPLES, regSamplerecno);
sqlite3VdbeAddOp3(v, OP_Lt, regSamplerecno, sqlite3VdbeCurrentAddr(v)+2,
regCount);
sqlite3VdbeAddOp2(v, OP_Integer, 0, regSamplerecno);
sqlite3VdbeAddOp2(v, OP_Copy, regFirst, regSamplerecno);
#endif
/* The block of memory cells initialized here is used as follows.
@@ -235,6 +240,7 @@ static void analyzeOneTable(
&& regTabname+2==regSampleno
&& regTabname+3==regCol
);
sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);
sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 4, regRec, "aaab", 0);
sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur+1, regRowid);
sqlite3VdbeAddOp3(v, OP_Insert, iStatCur+1, regRec, regRowid);
@@ -245,7 +251,7 @@ static void analyzeOneTable(
** samplerecno = samplerecno+(remaining records)/(remaining samples)
*/
sqlite3VdbeAddOp2(v, OP_AddImm, regSampleno, 1);
sqlite3VdbeAddOp3(v, OP_Subtract, regRecno, regCount, regTemp);
sqlite3VdbeAddOp3(v, OP_Subtract, regRecno, regLast, regTemp);
sqlite3VdbeAddOp2(v, OP_AddImm, regTemp, -1);
sqlite3VdbeAddOp2(v, OP_Integer, SQLITE_INDEX_SAMPLES, regTemp2);
sqlite3VdbeAddOp3(v, OP_Subtract, regSampleno, regTemp2, regTemp2);