stop double-buffering #1643
stop double-buffering #1643
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WalkthroughThe pull request introduces significant changes to the Changes
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Actionable comments posted: 3
🧹 Outside diff range and nitpick comments (2)
buffer.go (2)
26-27: Clarify Buffer Field Comments for Better ReadabilityThe comments for the
bufandcachedBuffields can be improved for clarity. Consider updating them to provide more context about their usage.Suggested change:
- buf []byte // read buffer. - cachedBuf []byte // buffer that will be reused. len(cachedBuf) <= maxCachedBufSize. + buf []byte // Current read buffer slice. + cachedBuf []byte // Reusable buffer for reading; maintains a max length of maxCachedBufSize.
113-124: Avoid Redundant Buffer Allocation intakeBufferIn the
takeBuffermethod, when the requestedlengthexceedslen(b.cachedBuf)but is less thanmaxCachedBufSize, you create a new buffer and assign it tob.cachedBuf. This could lead to unnecessary allocations iftakeBufferis called with varying sizes.Consider adjusting the logic to reuse the existing
cachedBufwhen possible or to limit how oftencachedBufis reassigned.Suggested change:
if length <= len(b.cachedBuf) { return b.cachedBuf[:length], nil } if length < maxCachedBufSize { - b.cachedBuf = make([]byte, length) - return b.cachedBuf, nil + buf := make([]byte, length) + copy(buf, b.cachedBuf) + return buf, nil }This way,
cachedBufremains stable, and you return a new buffer without altering the cached one.
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buffer.go(4 hunks)rows.go(0 hunks)
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- rows.go
🔇 Additional comments (1)
buffer.go (1)
146-149: Ensure Full Capacity is Returned in takeCompleteBuffer
The takeCompleteBuffer method returns b.cachedBuf, but if b.cachedBuf has been resized elsewhere, it might not have the expected capacity.
Please verify that b.cachedBuf maintains its capacity throughout its usage and that no unintended resizes occur.
| if b.busy() { | ||
| return nil, ErrBusyBuffer | ||
| } | ||
| return b.buf[:length], nil | ||
| return b.cachedBuf[:length], nil |
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Check for Buffer Capacity Before Slicing in takeSmallBuffer
In takeSmallBuffer, ensure that cachedBuf has sufficient capacity before slicing to prevent potential out-of-bounds errors.
Suggested change:
if b.busy() {
return nil, ErrBusyBuffer
}
+if length > len(b.cachedBuf) {
+ return nil, ErrBadLength
+}
return b.cachedBuf[:length], nilYou'll need to define ErrBadLength appropriately.
Committable suggestion skipped: line range outside the PR's diff.
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Actionable comments posted: 0
🧹 Outside diff range and nitpick comments (3)
buffer.go (3)
26-29: Document thread safety guaranteesWhile the field documentation is clear, consider adding a comment about thread safety guarantees of the buffer struct, especially since it's used for both reading and writing operations.
Add a comment like:
type buffer struct { + // Note: buffer is not safe for concurrent use. Callers must ensure + // synchronization when sharing buffer instances across goroutines. buf []byte // read buffer. cachedBuf []byte // buffer that will be reused. len(cachedBuf) <= maxCachedBufSize.
Line range hint
47-89: Several improvements needed in fill operation
- The buffer assignment on line 58 appears incorrect
- Missing input validation
- Buffer growth could be optimized
Consider these improvements:
func (b *buffer) fill(need int) error { + if need < 0 { + return fmt.Errorf("negative read size: %d", need) + } dest := b.cachedBuf if need > len(dest) { - dest = make([]byte, ((need/defaultBufSize)+1)*defaultBufSize) + // More efficient growth: round up to power of 2 + newSize := 1 << uint(math.Ceil(math.Log2(float64(need)))) + dest = make([]byte, newSize) if len(dest) <= maxCachedBufSize { - b.cachedBuf = dest + b.cachedBuf = b.buf } }
153-156: Consider adding buffer validation and memory managementThe store operation could benefit from additional safeguards:
Consider these improvements:
func (b *buffer) store(buf []byte) { + // Don't store nil or empty buffers + if len(buf) == 0 { + return + } if cap(buf) <= maxCachedBufSize && cap(buf) > cap(b.cachedBuf) { b.cachedBuf = buf[:cap(buf)] } }Also, consider adding a comment explaining the memory management strategy for stored buffers.
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buffer.go(4 hunks)packets.go(1 hunks)rows.go(0 hunks)
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- rows.go
🔇 Additional comments (5)
buffer.go (4)
35-36: LGTM: Buffer initialization is correct
The initialization of cachedBuf with defaultBufSize is appropriate and aligns with the new single-buffer design.
42-42: LGTM: Clear and explicit buffer state check
The change to directly check len(b.buf) is more explicit and correctly indicates if there's unread data in the buffer.
96-105: LGTM: Efficient read implementation
The read operation is well-implemented with clear buffer management and proper documentation about buffer validity.
26-29: Verify Go 1.20 compatibility removal
Since this PR removes double buffering based on dropping Go 1.20 support, let's verify there are no remaining Go 1.20 compatibility checks.
✅ Verification successful
Go 1.20 compatibility has been properly removed
The codebase has been successfully updated to remove Go 1.20 compatibility:
go.modexplicitly sets Go 1.21 as minimum version- No Go 1.20-specific code or compatibility checks remain
- The only Go version constraint found is for Go 1.18 in
dsn_fuzz_test.go, which is unrelated to the buffer changes - Historical mentions in CHANGELOG.md don't affect the current implementation
🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash
# Search for any remaining Go 1.20 compatibility code or comments
rg -i "go 1\.20|go1\.20"
# Search for any build tags related to Go versions
rg "//\s*\+build\s+.*go1\."
Length of output: 165
Script:
#!/bin/bash
# Check go.mod for minimum Go version requirement
cat go.mod | grep -E "^go\s+"
# Look for any other potential Go version checks in the code
rg "runtime\.Version|go1\." -A 2
# Check if there are any other build constraints
fd --extension go --exec head -n 5 {}
Length of output: 7428
packets.go (1)
1194-1194: LGTM! Buffer error handling simplified.
The removal of error handling for mc.buf.store(data) aligns with the PR objective of eliminating double buffering. This simplification is safe as the buffer store operation cannot fail in the new single-buffer implementation.
Let's verify that all buffer error handling has been consistently updated:
✅ Verification successful
Buffer store operation correctly simplified
The verification confirms that the removal of error handling for mc.buf.store(data) is consistent with the codebase's buffer implementation. Key findings:
- Only one instance of
buf.store()exists, which is the simplified version in the PR - Other buffer operations (
takeBuffer,readNext, etc.) maintain their error handling as they deal with I/O operations - The buffer is properly managed within the
mysqlConnstruct
🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash
# Description: Check for any remaining error handling of buffer store operations
# that might have been missed during the transition to single buffering.
# Search for error handling patterns around buffer store operations
rg -A 2 -B 2 'buf\.store\('
# Search for any remaining double buffer related code
ast-grep --pattern 'if err := $_.store($_); err != nil {
$$$
}'
Length of output: 295
Script:
#!/bin/bash
# Let's get more context around buffer operations to ensure consistency
# Search for all buffer-related operations
rg -A 5 -B 5 'buf\.'
# Also check for any error handling patterns around buffer operations
rg -A 3 'if.*err.*:=.*buf\.'
# Look for any buffer-related type definitions and methods
ast-grep --pattern 'type $_ struct {
buf $_
$$$
}'
Length of output: 9185
Description
Since we dropped Go 1.20 support, we do not need double buffering.
This pull request stop double buffering and simplify buffer implementation a lot.
Fix #1435
Checklist
Summary by CodeRabbit
New Features
Bug Fixes
Closemethod in the MySQL rows handling to eliminate unnecessary buffer operations, ensuring cleaner resource management.These updates enhance the overall performance and reliability of the application.